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Microbial
Biotechnology
An Interdisciplinary Approach
Microbial
Biotechnology
An Interdisciplinary Approach
Pratyoosh Shukla
CRC Press
Taylor & Francis Group
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Boca Raton, FL 33487-2742
© 2017 by Taylor & Francis Group, LLC
CRC Press is an imprint of Taylor & Francis Group, an Informa business
No claim to original U.S. Government works
Printed on acid-free paper

Version Date: 20161019
International Standard Book Number-13: 978-1-4987-5677-8 (Hardback)
This book contains information obtained from authentic and highly regarded sources. Reasonable
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Contents
Foreword, vii
Preface, ix
Contributors, xi
Chapter 1 ◾ Bacterial Exopolysaccharides: Major Types

and Future Prospects 1
Aparna Banerjee and R ajib Bandopadhyay
Chapter 2 ◾ Bioremediation: A Novel Green Technology

to Clean Up the Highly Contaminated
Chromites Mining Sites of Odisha 21
Swati Sucharita Panda and Nabin Kumar Dhal
Chapter 3 ◾ Recent Developments in Food Biotechnology

to Improve Human Health with Probiotics
with Special Emphasis on Lowering Cholesterol 35
Renu Agrawal
Chapter 4 ◾ Molecular Characterization and

Quantification of Microbial Communities in
Wastewater Treatment Systems 59
Jashan Gokal, Oluyemi Olatunji Awolusi, Abimbola
Motunrayo Enitan, Sheena Kumari, and Faizal Bux
Chapter 5 ◾ Thermostable Enzymes and Their Industrial

Applications 115
Santhosh Kumar, Nanthakumar Arumugam,
Kugenthiren Permaul, and Suren Singh
v
vi ◾ Contents
Chapter 6 ◾ Microbial Enzymes for Pulp and Paper

Industry: Prospects and Developments 163
Puneet Pathak, Prabhjot K aur, and Nishi K. Bhardwaj
Chapter 7 ◾ Rhizobacteria: Tools for the Management

of Plant Abiotic Stresses 241
Anjali Singh, Ajay Shankar, Vijai Kumar Gupta, and Vishal Prasad
Chapter 8 ◾ Betulin Biotransformation toward Its

Antitumor Activities: A Brief Overview 263
Dhirendra Kumar and K ashyap Kumar Dubey
Chapter 9 ◾ Optimizing the Performance of Wastewater

Treatment Plants and Effluent Quality Using
Evolutionary Algorithms 287
Abimbola Motunrayo Enitan, Josiah Adeyemo, Gulshan Singh,
and Folasade Adeyemo
Chapter 10 ◾ Production of Fructooligosaccharides as

Ingredients of Probiotic Applications: Future
Scope and Trends 311
Ruby Yadav, Puneet Kumar Singh, and Pratyoosh Shukla
Chapter 11 ◾ Avenues in Ophthalmic Optical Coherence

Tomography in Medical Biotechnology:
Prospects and Future Trends 325
R aju Poddar, Vinod Aggarwal, Varun Gogia, Mayank Bansal,
Shika Gupta, Rohan Chawla, and Pradeep Venkatesh
INDEX349
Foreword
T he book Microbial Biotechnology: An Interdisciplinary Approach,

edited by Dr. Pratyoosh Shukla, covers some of the latest applications
of microorganisms from a practical point of view. The field of microbial
biotechnology, in the context of the so-called cell factories, is of great
interest and the number of groups involved in such projects is growing
exponentially.
Although the book chapters cover different aspects of microbial bio-
technology, I want to highlight two of them. The first refers to the field
of functional foods; several chapters deal with the production of probiot-
ics and prebiotics, and their effect on gastrointestinal health. The second
topic is microbial bioremediation, which is exemplified in this book by
the use of microbes to clean up mining sites and by the optimization of
wastewater treatments. Other issues having a significant impact are also
addressed in the book: for example, the use of microbial enzymes in pulp
and paper industries, the different applications of exopolysaccharides, or
the latest developments in medical biotechnology, among others.
In summary, there is no doubt about the interest of the contents dis-
played in this book. I am sure that the book Microbial Biotechnology: An
Interdisciplinary Approach will provide the scientific community with
great benefits for the coming years.
Francisco Plou
Research Scientist at Spanish CSIC
Honorary Professor at Autonomous University of Madrid
Madrid, April 4, 2016
vii
Preface
T he book describes the interdisciplinary scope of biotechnology

and discoveries thereof. This book briefs the reader on various novel and
innovative ideas of emerging biotechnology. The key features are described
below to highlight the important contents of the book:
1. The book envisages the recent ideas of novel findings in microbiology.

2. It also provides insights into various interdisciplinary research
avenues.
3. There are very few books available covering the diversity of topics
described in this book.
4. Some key areas of modern biotechnology are also covered in this
book, which are not available in any such books in the market.
5. Enhanced and simplified descriptions are the key components of
this book, which provide unique benefits to its readers.
This book will also act as an important means of information on research-

ers working in interdisciplinary areas of research. The chapters outlined
in this book cater to the needs of researchers working in the areas of bac-
terial exopolysaccharides, microalgal proteomics, applications of micro-
bial L-asparaginases, novel aspects of bioremediation, probiotics and their
impact on society, microbial community analysis in wastewater treatment
techniques, etc. The book focuses on describing the above-mentioned
aspects and on diversifying the understanding of microbial biotechnology
to an expanded level.
ix
x ◾ Preface
This book will be a valuable resource to senior undergraduate and grad-

uate students, researchers, professionals, and other interested individuals
or groups working in the areas mentioned in the book.
Pratyoosh Shukla, PhD

December 2016
Rohtak, India
Contributors
Folasade Adeyemo Oluyemi Olatunji Awolusi

Institute for Water and Wastewater Institute for Water and Wastewater
Technology (IWWT) Technology
Durban University of Durban University of Technology
Technology Durban, South Africa
Durban, South Africa
Rajib Bandopadhyay
Josiah Adeyemo Department of Botany
Department of Civil and The University of Burdwan
Structural Engineering Burdwan, West Bengal, India
Masinde Muliro University of Aparna Banerjee
Science and Technology Department of Botany
Kakamega, Kenya The University of Burdwan
Burdwan, West Bengal, India
Vinod Aggarwal
Dr. Rajendra Prasad Centre for Mayank Bansal
Ophthalmic Sciences Dr. Rajendra Prasad Centre for
A.I.I.M.S. Ophthalmic Sciences
New Delhi, India A.I.I.M.S.
New Delhi, India
Renu Agrawal
Nishi K. Bhardwaj
CSIR-CFTRI and Rural
Avantha Centre for Industrial
Development Programme
Research & Development
Mysore, India
Yamuna Nagar, Haryana, India
Nanthakumar Arumugam Faizal Bux
Department of Biotechnology Institute for Water and Wastewater
and Food Technology Technology (IWWT)
Durban University of Technology Durban University of Technology
Durban, South Africa Durban, South Africa
xi
xii ◾ Contributors
Rohan Chawla Shika Gupta

Dr. Rajendra Prasad Centre for Dr. Rajendra Prasad Centre for
Ophthalmic Sciences Ophthalmic Sciences
A.I.I.M.S. A.I.I.M.S.
New Delhi, India New Delhi, India
Nabin Kumar Dhal Vijai Kumar Gupta

Environment and Sustainability School of Natural Sciences
Department NUI Galway
CSIR-IMMT Galway, Ireland
Bhubaneswar, India
Prabhjot Kaur
Kashyap Kumar Dubey Avantha Centre for
University Institute of Industrial Research &
Engineering and Technology Development
(UIET) Yamuna Nagar, Haryana, India
Maharshi Dayanand University
Rohtak, Haryana, India Dhirendra Kumar
Department of Biotechnology
Abimbola Motunrayo Enitan University Institute of
Institute for Water and Wastewater Engineering and Technology
Technology (IWWT) (UIET)
Durban University of Technology Maharshi Dayanand University
Durban, South Africa Rohtak, Haryana, India
Varun Gogia Santhosh Kumar

Dr. Rajendra Prasad Centre for Department of Biotechnology and
Ophthalmic Sciences Food Technology
A.I.I.M.S. Durban University of Technology
New Delhi, India Durban, South Africa
Jashan Gokal Sheena Kumari

Institute for Water and Wastewater Institute for Water and Wastewater
Technology Technology (IWWT)
Durban University of Technology Durban University of Technology
Durban, South Africa Durban, South Africa
Contributors ◾ xiii
Swati Sucharita Panda Anjali Singh

Environment and Sustainability Institute of Environment and
Department Sustainable Development
CSIR-IMMT Banaras Hindu University
Bhubaneswar, India Varanasi, India
Puneet Pathak
Gulshan Singh
Avantha Centre for Industrial
Institute for Water and Wastewater
Research & Development
Technology (IWWT)
Yamuna Nagar, Haryana, India
Durban University of
Kugenthiren Permaul Technology
Department of Biotechnology and Durban, South Africa
Food Technology
Durban University of Technology Puneet Kumar Singh
Durban, South Africa Department of Microbiology
Maharshi Dayanand University
Raju Poddar Rohtak, Haryana, India
Department of Bioengineering
Birla Institute of Technology
Ranchi, India Suren Singh
Department of Biotechnology and
Vishal Prasad Food Technology
Institute of Environment and Durban University of
Sustainable Development Technology
Banaras Hindu University Durban, South Africa
Varanasi, India
Pradeep Venkatesh
Ajay Shankar
Dr. Rajendra Prasad Centre for
Institute of Environment and
Ophthalmic Sciences
Sustainable Development
A.I.I.M.S.
Banaras Hindu University
New Delhi, India
Varanasi, India
Pratyoosh Shukla Ruby Yadav

Department of Microbiology Department of Microbiology
Maharshi Dayanand University Maharshi Dayanand University
Rohtak, Haryana, India Rohtak, Haryana, India
Chapter 1
Bacterial
Exopolysaccharides
Major Types and Future Prospects
Aparna Banerjee and Rajib Bandopadhyay
CONTENTS
Abstract.................................................................................................................2
Introduction.........................................................................................................2
EPS Producing Bacteria: Major Types..............................................................4
Soil Inhabitants...............................................................................................4
Lactic Acid Bacteria.......................................................................................4
Halophiles........................................................................................................4
Thermophiles..................................................................................................8
Psychrophiles..................................................................................................8
EPS from Pathogenic Bacteria.................................................................8
Regulation of EPS Production...........................................................................9
Present Studies on Bacterial EPS.....................................................................10
Heteropolysaccharides.................................................................................10
Homopolysaccharides..................................................................................12
Future Prospects of Bacterial EPSs.................................................................13
Food Industry................................................................................................13
Pharmaceutical Industry.............................................................................13
Biomedical Application...............................................................................14
Bioremediation and Wastewater Treatment..............................................14
Patenting in the Field of Bacterial EPS...........................................................14
Conclusion.........................................................................................................16
Acknowledgment...............................................................................................17
References...........................................................................................................17
1
2 ◾ Microbial Biotechnology
ABSTRACT
Exopolysaccharide (EPS) is secreted by bacteria for their survival in harsh
environmental conditions as a protective mechanism. Repeating sugar
units, attached with proteins, lipids, organic and inorganic compounds,
metal ions, and DNA are found in EPS. Bacterial EPSs have possible com-
mercial applications in pharmaceutical industry, food processing, drug
detoxification, bioremediation, and in many more. The most used and
patented bacterial EPSs are xanthan, cellulose, gellan, alginate, etc. Varied
applications of microbial EPSs are somewhat unexplored and their study
is persistently enhancing toward isolation and characterization of novel
EPSs as renewable capital. Downstream processing for purification and
genetic engineering for increased EPS biosynthesis require more attention.
INTRODUCTION
Polysaccharides is an important content of microbial cell walls, either as
storage capsular polysaccharides or as biofilm called as exopolysaccharides
(EPSs) secreted by microbes in its surrounding. Presently, isolation and
characterization (Figure 1.1) of new microbial EPS is of key scientific inter-
est, because EPS has shown promising application as texture enhancers,
gelling agents, emulsifiers, viscosifiers, and also as the newest nanovector
for drug delivery, resulting in sustained release of drugs. Bacterial EPS own
a varied range of property which is not found in traditional plant polymers.
Although it competes for algal (alginates, carrageenans, and ulvan), crus-
tacean (chitin) or plant polysaccharides, its production level is less due to
green house effect, global warming, marine pollution, sea level increment,
loss of key stone species, crop failure, and overall climate change impacts.
Microorganisms provide a controlled production in bioreactors, with-
out any variation due to the physiological states encountered for higher
organisms (1). But downstream processing of bacterial polysaccharides has
cost-intensive steps, as the expenses needed for substrates requirement for
microbial growth and bioreactors are too high (2). Moreover, cultivation
of microorganisms in a fermenter allows growth optimization and pro-
duction yield either by physiological study or by genetic modification. For
high-value pharmaceutical industry, bacterial polysaccharides can be pro-
duced at a feasible economic cost. Research in the field of bacterial EPS pro-
duction is till now done on most available EPSs such as cellulose, xanthan
gum, levan, glucan, cellulose, sphigan, hyaluronan, and succinoglycan, of
which xanthan gum from Xanthomonas sp., gellan from Sphingomonas
Bacterial Exopolysaccharides ◾ 3
Centrifugation of microbial culture
Isolation of supernatant
Precipitation of EPS using

methanol, ethanol, or iso-propanol
Isolation of EPS from

centrifugated pellet and vacuum drying
Morphological Physical characterization Chemical

characterization characterization
Molecular weight
Fluorescence microscopy determination GC-MS, HPLC
Total carbohydrate FTIR
Scanning electron
content
microscopy 1
H NMR and 13C NMR
CHNS analysis
Thermo gravimetric
analysis
FIGURE 1.1 Flowchart elucidating the main steps of isolation and characteriza-
tion of bacterial EPS.
elodea and Sphingomonas paucimobilis, cellulose from Gluconacetobacter

xylinus, alginate from Pseudomonas aeruginosa and Pseudomonas putida,
levan from Zymomonas mobilis and Halomonas eurihalina, succinoglycan
from Agrobacterium radiobacter, Rhizobium meliloti, and Agrobacterium
tumefaciens, Glucan from Leuconostoc dextranicum show strong potential
commercial uses. All of these are very closely related structures and share
high level of homology in many biosynthetic pathways.
The word EPS is first termed by Sutherland (3) for high molecular
weight marine bacterial carbohydrate polymers. EPSs are produced in
large amounts surrounding the microbial cells in extreme environments
of Antarctic ecosystems, hypersaline lakes, hot water springs, or in deep-
sea hydrothermal vents. Among all other adaptations for survival in
extreme conditions, such as high temperatures, extreme salt levels, low
pH, temperature variation, and high radiation zone, EPS biosynthesis is
the most common protective mechanism by extremophilic microorgan-
isms. EPS producing bacteria can be screened by the presence of glossy
and slimy colony appearance, so that they can be further chosen for mass
production (4).
EPS PRODUCING BACTERIA: MAJOR TYPES

Several groups of bacteria are capable of EPS production and they can be
broadly categorized into five groups (Table 1.1): soil inhabitants, lactic acid
bacteria, halophiles, thermophiles, and psychrophiles.
Soil Inhabitants
The most famous EPS producers are soil inhabiting rhizobia. It forms
large amounts of polysaccharides when grown in pure cultures and also
into the rhizosphere. Rhizobium meliloti, Rhizobium leguminosarum, and
Rhizobium tropici are the three most studied EPS producing soil inhab-
iting bacteria (5,6). Regulation of motility related genes and presence of
quorum sensing proteins in rhizobia resulted into a complex EPS bio-
synthesis pathway. EPS production by bacteria and biofilm formation
enhances soil fertility and improved plant growth (7). Pantoea (formerly
Enterobacter) agglomerans isolated from mangrove forest had very high
ultraviolet radiation tolerance. The water-soluble EPS was extracted and
was further tested for its ultraviolet radiation protection and free radical
scavenging activities (8). Micrococcus luteus isolated from Egyptian soil,
produced a maximum of 13 g/L EPS and the EPS showed high antioxidant
activity (9).
Lactic Acid Bacteria

Lactic acid bacteria (LAB) improve the flavor, aroma, and texture of
milk, meat, and vegetables and therefore they are used in food fermenta-
tions. LAB usually produce small amounts of EPS (100–200 mg/L) (10)
but Lactobacillus sakei produced up to 4 g/L EPS (11). In fermented milk
(12) and during cheese production (13), small amounts of EPS produc-
tion change the texture and properties of the products. Several strains
of Streptococcus thermophilus produce EPS in milk or in same type of
media. The thermophilic LAB are also capable of producing EPS, such as
Streptococcus thermophilus and Lactobacillus delbrueckii (12).
Halophiles
The diversity of halophilic bacteria so far isolated and characterized can be
categorized into four different classes according to its salt requirement for
their growth, which include slight halophiles, moderate halophiles, extreme
TABLE 1.1 Recent Studies on Bacterial Exopolysaccharides, Its Chemical Composition, and Probable Function
Bacterial Type Bacterial Strain Maximum EPS Constituents of EPS Function of EPS References
Production
Soil inhabitant Pseudomonas 4.5 g/L Fructose:glucose:mannose = 4:1:0.6. NMR indicated Phosphate solubilizing Taguett et al.
fluorescens EPS produced was levan with β-(2 → 6)-linked activity (32)
fructose units
Rhizobium tropici 4.08 g/L Mannose (0.86%, 1.49%, and 2.68%), rhamnose Shear-resistant nature, Lemos et al.
(2.58%, 2.49%, and 0.60%), glucuronic acid (8.6%, soil stabilizing agent (5)
5.97%, and 3.57%) and trace of galacturonic acid
Micrococcus luteus 13 g/L Mannose:arabinose:glucose:glucuronic In vitro DPPH Asker et al.
acid = 3.6:2.7:2.1:1.0 radical-scavenging (33)
Main backbone consists of mannose units linked activity, with an EC50
with (1 → 6) glycosidic bonds and arabinose units value of 180 µg/mL
linked with (1 → 5) glycosidic bonds. There is a side
chain consisting of mannose units linked with
(1 → 6) glycosidic bonds at C3, when all glucose and

most of glucuronic acid are found in the side chain.
Lactic acid Lactobacillus sakei 2 g/L and IR spectra of both EPS were same as commercial Antiviral and Vázquez et al.
bacteria and Leuconostoc 1.4 g/L dextran; specifically α-(1 → 6) glucan with immunomodulatory (34)
mesenteroides approximately 6% substituted side chain glucose activity
Lactobacillus – Mannose:fructose:galactose:glucose = 8.2:1:4.1:4.2 Antibacterial, Wang et al.
plantarum antioxidant, and (35)
anticancerous activity
Streptococcus 12.14 g/L – Antibacterial, Kanmani
phocae antioxidant, and et al.(36)
flocculating activity
(Continued)
TABLE 1.1 (Continued) Recent Studies on Bacterial Exopolysaccharides, Its Chemical Composition and Probable Function
Maximum EPS
Bacterial Type Bacterial Strain Production Constituents of EPS Function of EPS References
Streptococcus Tetrasaccharide of glucose: galactose = 1:1 and – Marshall
thermophilus and heptasaccharide composed of et al. (37)
Lactobacillus galactose:glucose:rhammose = 5:1:1
Delbrueckii
Halophile Halomonas 3.89 g/L Monosaccharide (%): glucose (24 ± 1.73), glucuronic Flocculating and Amjres et al.
stenophila acid (7.5 ± 0.37), mannose (5.5 ± 0.17), fucose emulsifying activities (38)
(4.5 ± 0.36), galactose (1.2 ± 0.17), and rhamnose
(1 ± 0.05)
Halomonas 1.7 g/L Monosaccharide: 72% mannose, 27.5% glucose, and Emulsifying Llamas et al.
almeriensis 0.5% rhamnose. hydrophobic (39)
Low-molecular-weight EPS: 1.1% protein, 70% substrates and
mannose, and 30% glucose pseudoplasticity
Thermophile Brevibacillus 2.08 g/L Glucose:galactose:mannose: Nonpathogenic Yildiz et al.
thermoruber galactosamine:mannosamine =57.7:16.3:9.2:14.2:2.4 promising EPS (25)
Geobacillus 1.12 g/L Carbohydrate content = 98% Anti-cytotoxic activity Kambourova
tepidamans Protein content = 1.8% against Avarol et al. (24)
Uronic acids = 0.2%
(Continued)
TABLE 1.1 (Continued) Recent Studies on Bacterial Exopolysaccharides, Its Chemical Composition and Probable Function
Maximum EPS
Bacterial Type Bacterial Strain Production Constituents of EPS Function of EPS References
Psychrophile Pseudoalteromonas – – Inhibitory activity Chen et al.
sp. S-5 against human (40)
leukemia K562 cells
Pseudomonas sp. – Carbohydrate content = 33.81% ± 2.59, composed of Emulsifier and Mercade
ID1 glucose (17.04% ± 0.32), galactose (8.57% ± 1.15), cryoprotector et al. (41)
and fucose (8.21% ± 1.12). Total uronic acid
content = 2.40% ± 0.33%.

Pseudoalteromonas 8.61 g/L – Cryoprotector Liu et al. (42)
sp. strain
SM20310
Zunongwangia Highly complex α-mannan polymer of 2-α-, Cryoprotector Liu et al. (28)
profunda 6-α-mannosyl residues, where 6-α-mannosyl
residues are branched at 2nd position with 1–2
t-mannosyl residues
halophiles, and borderline halophiles. The halotolerant bacteria in con-

trast show tolerance to a wide range of salinity stress, from high salt con-
centration to zero salt requirement (14). Many halophilic Archaea such as
Haloferax, Haloarcula, Halococcus, Natronococcus, and Halobacterium are
also good EPS producers (15–17). H. maura, H. eurihalina, H. ventosae,
and H. Anticariensis of Halomonas genus are the most dominant halo-
philic EPS producing group. The characteristic features of EPS synthesized
by Halomonas strain are unusually high sulfate content and uronic acids in
large amounts which result in good jellifying properties (18). Most halophiles
show high levels of heavy metal resistance as it is found in coastal areas.
Thermophiles
Thermophiles are currently classified as: moderate thermophiles (50–
70°C) and extremothermophiles (>70°C) based on its optimal growth
temperatures; extremothermophiles grow optimally above 80°C and are
also termed as “hyperthermophiles.” They inhabit a wide range of habitats
from geothermal springs and solfataric (sulfur) fields, shallow submarine
hydrothermal systems, geothermally heated oil reservoirs to abyssal hot-
vent environments or hot coal-refuse piles (19).
Different hyperthermophilic microorganisms such as Thermotoga
maritima, Archaeoglobus fulgidus, and Thermococcus litoralis produce EPS
significantly (20–22). Works has also been done on EPS producing Bacillus
licheniformis from marine hot springs (23), glucan producing Geobacillus
tepidamans from Bulgarian hot springs (24), Brevibacillus thermoruber
from geothermal springs of Turkey and Bulgaria (25).
Psychrophiles
A large portion of reduced carbon reserve of the ocean is EPS and it
enhances the survival rate of psychrophilic marine bacteria by modify-
ing the physicochemical environment around the bacterial cell. Antarctic
marine environments are rich in bacterial EPSs which help the micro-
bial communities to survive under extreme cold temperature and salin-
ity with least nutrient availability. EPS produced by a new genus of
Pseudoalteromonas, isolated from Antarctic sea ice at −2°C and 10°C
showed higher uronic acid content than EPS produced at 20°C (26).
EPS from Pathogenic Bacteria

Surface attaching bacteria come together in a hydrated polymeric matrix
for biofilm formation. EPS biosynthesis by these virulent communities
results in resistance to antimicrobial drugs, which is the root to many

chronic and persistent bacterial infections. Bacterial EPS is also the basis
of growth of pathogenic microorganism in biofilms as it provides the sub-
stratum for microbial growth in mats; for example, dental caries by acido-
genic Gram-positive cocci, cystic fibrosis pneumonia by Pseudomonas
aeruginosa and Burkholderia cepacia, nosocomial infection by different
Gram-negative bacteria are all biofilm-mediated infection. Nitric-oxide-
mediated signaling results in EPS production in Shewanella oneidensis.
LasI-dependent QS provides maturation signal and results in the forma-
tion of a thick and differentiated biofilm of Pseudomonas aeruginosa.
Presently, diguanylate cyclase and its product cyclic di-guanosine mono-
phosphate (c-di-GMP) are key biomedical targets for the inhibition of
biofilm development.
REGULATION OF EPS PRODUCTION

A complex process involving the transport of organic and inorganic mol-
ecules to the outer surface, its adsorption to that surface and finally the
formation of an unalterable attachment result in the growth of EPS as bio-
film. The most studied regulatory mechanism controlling EPS production
is QS. QS maintains bacterial intercellular communication and regulate
gene-specific expression to increase cell density.
Two QS processes described in bacteria are AI-1 and AI-2. Autoinducer-1
(AI-1) regulates intraspecies communication and AI-2 regulates interspe-
cies communication. Gram-negative bacteria secrete AI molecule: N-acyl
homoserine lactone (AHL) that control cell density. The detection of accu-
mulated AHL signal by bacteria switches on transcriptional effectors to
activate silent genes above a certain threshold concentration. This results
into cell density dependent gene expression and behavioral change. Gram-
positive bacteria communicate with modified oligopeptides and mem-
brane-bound histidine kinase sensor as receptors. Signaling is controlled
by multiple phosphorylations which modify the activity of the regulator
(27). The omnipresent bacterial c-di-GMP is an important messenger in
controlling bacterial biofilm formation. Cyclic nucleotides are synthe-
sized by external stimuli on various signaling domains within N-terminal
region of dimeric diguanylate cyclase. It initiates condensation of two
molecules of guanosine triphosphate opposite to each other within the
C-terminal region of the enzyme. Additionally, the formation of a long-
term stable aerobic granule, a superior biofilm for biological wastewater
treatment, can be controlled by stimulating c-di-GMP.
Substrate (a) is first catabolized by glycolytic pathways into pyruvate

while entering the cell. Under aerobic conditions, it is converted to acetyl-
CoA and enters TCA cycle (b). UDP-Glc, UDP-Gal, and GDP-Man are
interconverted by epimerization, oxidation, decarboxylation, reduction,
and rearrangement (c) reactions to form energy-rich monosaccharide tri-
phosphates. EPS biosynthesis and polymerization occurs through any of
the following mechanisms (d).
Wzx–Wzy system (left) synthesize EPS by the sequentially transferring
monosaccharides from NDP-sugars to a polyprenylphosphate lipid carrier.
For polymerization by polymerase enzyme Wzy, modified repeating units
are transported across the inner membrane by a flippase enzyme Wzx to
the periplasmic place. Polysaccharide copolymerase (PCP) determines the
polymer length, while an outer membrane polysaccharide export protein
OPX forms the intermembrane channel.
The ABC-transporter system (right) results in EPS formation at the
cytoplasmic side of the inner membrane by adding sugar residues to the
nonreducing end of the polymer and export it across the inner membrane,
followed by its translocation across the outer membrane by PCP and OPX
(Figure 1.2).
PRESENT STUDIES ON BACTERIAL EPS

Microbial EPSs are usually linear molecules with different side chains.
Association of high molecular weight polymer chains results in complex
entanglement. These high molecular weight polymers show a tendency
to form double-stranded helices (kappa carrageenans, xanthan, succino-
glycan, and gellan) and sometimes triple stranded (curdlan, schizophyl-
lan) (28,29) also. Commonly found monosaccharides in bacterial EPSs
are d-glucose, d-galactose, and d-mannose; l-fucose and l-rhamnose;
and N-acetylhexosamines, N-acetyl-d-glucosamine, and N-acetyl-d-
galactosamine. Uronic acids such as d-glucuronic and d-galacturonic acid
are also present in few microbial EPSs. Common and commercially most
exploited types of bacterial EPSs (Figure 1.2) are xanthan, gellan, cellu-
lose, sphingan, hyaluronan, alginate, etc.
Heteropolysaccharides
1. Xanthan gum: It is the first industrially produced biopolymer,
which is extensively studied and widely accepted commercially.
Xanthomonas genus of bacteria secretes this heteropolysaccharide
(a)
ADP + Pi Substrate
ATP Glycerol
Glucose
Fructose
Man-6-P Glucose-6-P
Fructose-6-P
(c) ADP + Pi NAD+
Glycolysis
(b)
Man-1-P Glc-1-P ATP NADH + H+
Acetyl CoA
TDP-Glc Pyruvate
UDP-Glc CO2
GDP-Man
FADH2 TCA NAD+
cycle
FAD NADH + H+
GDP-Fuc TDP-Rha UDP-Gal UDP-GlcA
ATP ADP + Pi
NDP-sugars
NDPs
NMP
NDPs ADP + Pi
(d) NMP
NDP-sugars
Cytoplasm
NDP-sugars ATP ABC

P
Wzy Wzx P
PCP
Inner membrane
PCP
P P
P P
Peptidoglycan
OPX
OPX
Outer membrane
EPS EPS Extracellular

environment
FIGURE 1.2 Schematic diagram showing biosynthetic pathways of EPS syn-

thesis by Gram-negative bacteria. (a) Substrate entry to the cell, (b) entry
of phosphorylated sugars in TCA cycle, (c) interconversion of sugars, and
(d) EPS polymerization. Fuc, fucose; Gal, galactose; Glc, glucose; GlcA, gluc-
uronic acid; Man, mannose; Rha, rhamnose; GDP, guanosine diphosphate;
TDP, tyrosine diphosphate; NMP, nucleoside monophosphate. (Adapted
from Freitas, F., Alves, D. V., and Reis, M. A. M. 2011. Trends in Biotechnology
29:388–398.)
and it has a glucose backbone with trisaccharide side chain of gluc-

uronic acid, mannose, pyruvil, and acetyl residues.
2. Sphingans: These are heteropolysaccharides produced by members
of the genus Sphingomonas having a characteristic tetrasaccharide
backbone of rhamnose, glucose, and glucuronic acid. Different vari-
ations of sphingans are gellan, welan, rhamsan, and diutan. They
have difference in composition and linkage of the side chains, for
example, gellan contains acetyl and glyceryl residues in side chain,
whereas welan has a rhamnose or mannose containing a side chain
branch.
3. Hyaluronan: Repeating disaccharide units of glucuronic acid and
N-acetylglucosamine form a linear structured polymer named
hyaluronan. Bacterial strains, for example, Pseudomonas aeru-
ginosa and group A and C Streptococci attenuated strains are
observed to produce this high market value EPS.
4. Succinoglycan: This is a branched bacterial EPS with glucose and
galactose backbone and tetrasaccharide side chains of glucose resi-
dues. Succinate, pyruvate, and acetate are also commonly found in
it. Many soil inhabiting bacteria such as Rhizobium sp., Alcaligenes
sp., Pseudomonas sp., and Agrobacterium sp. are good producers of
succinoglycan.
5. Alginate: This is a linear copolymer of block-structured poly-
mannuronic acid and poly-guluronic acids. Alginate is secreted by
Pseudomonas aeruginosa and Azotobacter vinelandii. The main dif-
ference between algal and bacterial alginate is the algal one is an
acetylated polysaccharide.
Homopolysaccharides
1. Glucans: Glucans are glucose homopolysaccharides differing
in glycosidic bond, degree and type of branching, chain length,
molecular mass, and polymer conformations. Glucans are of two
types—α-glucans (reuteran, dextran, mutan, and alternan) and
β-glucans (e.g., cellulose and curdlan). Bacterial genera, such as
Gluconacetobacter, Agrobacterium, Aerobacter, Achromobacter,
Azotobacter, Rhizobium, Sarcina, and Salmonella are able to pro-
duce cellulose. Extracellular enzyme dextransucrase that form
α-glucans are produced from sucrose in several bacterial genera
of Lactobacillus Leuconostoc and Streptococcus. Substrate synthe-

sis for cellulose production starts from the glycolytic intermedi-
ate glucose-6-phosphate. Curdlan is glucans homopolysaccharide
of β-(1 → 3)-linked glucose residues produced by bacteria such as
Agrobacterium biobar and A. tumefaciens, and it forms characteris-
tic elastic gels after heating in aqueous suspension. Curdlan produc-
tion by Alcaligenes faecalis is developed for commercial use in gel
production.
2. Levan: It is synthesized from sucrose by the extracellular enzyme
levansucrase (EC 2.4.1.10), also known as sucrose 6-fructosyltrans-
ferase by several bacterial genera of Bacillus, Rahnella, Aerobacter,
Erwinia, Streptococcus, Pseudomonas, and Zymomonas (30). Levan
is highly branched water-soluble fructose homopolysaccharide.
Due to the presence of β-(2 → 6) linkage, levan is soluble in oil.
FUTURE PROSPECTS OF BACTERIAL EPSs

The future of bacterial EPS production will be glorious, as immense poten-
tial applications of EPS are already established in vitro. The most accepted
bacterial EPS as drug delivery systems are xanthan and cellulose. There
are many others and the most promising are the ones mentioned below.
Food Industry
First industrially marketed EPS dextran is produced by LAB and is used
in confectionary to improve moisture retention, maintenance of viscos-
ity, and to inhibit sugar crystallization. It acts as gelling agents in jelly
and gum. It inhibits water crystal formation in ice cream and also gives
the desired body and mouth feel in pudding. Due to the growing demand
in natural and minimally processed foods, the use of antimicrobial com-
pounds produced by LAB is of huge scientific and commercial interest as
a safe and natural food preservative. Nisin produced by Lactococcus lactis
and Reuterin produced by Lactococcus reuteri are widely used as natural
antibacterial food preservatives.
Pharmaceutical Industry
Recently there is a huge growing demand for LAB as probiotics. The
characteristic features of LAB strains as probiotics are its acid and bile
tolerance, producing antimicrobial compounds against pathogens and
adherence, and colonization in human intestinal mucosa.
Bacterial EPS xanthan gum synthesized by Xanthomonas campestris is

a sustained drug delivery system and increase drug effectivity. Bacterial
cellulose nanocrystals produced by Gluconacetobacter xylinus showed
superior properties than plant-derived cellulose and are recently patented
by FDA for using as transdermal drug delivery system, tablet excipient,
and aerogel–hydrogels.
Biomedical Application
Polysaccharides of marine Vibrio, Pseudomonas, and Bacillus lichenifor-
mis showed to have antitumor, antiviral, and immune stimulant activity.
Alteromonas infernus isolated from deep-sea hydrothermal vent, pro-
duced a low-molecular weight heparin-like EPS with good anticoagulant
property. An l-fucose containing polysaccharide Clavan showed prom-
ising roles in tumor cell colonization prevention in lung, regulation of
white blood-cell formation, rheumatoid arthritis treatment, antigen syn-
thesis for antibody production, and in cosmeceuticals as a skin mois-
turizing agent. Water-soluble EPS from Pantoea agglomerans showed
protective activity against UV radiation by its free radical scavenging
activity (8).
Bioremediation and Wastewater Treatment

Bacterial EPS can effectively perform bioremediation, as bacteria grow-
ing within the biofilm have higher adaptation to different extreme envi-
ronments and increased survival rate. Biofilm reactors are mainly used to
treat municipal and industrial wastewater. As EPSs have good floccula-
tion activity and are able to bind metal ions in solutions, it is used in the
removal of heavy metals from the environment. Sulfate reducing bacte-
ria, Enterobacter and Pseudomonas species are the major group of bacte-
ria commonly found in metal contaminated wastewaters and are highly
efficient in anaerobic degradation of organic pollutants and heavy metal
precipitation from wastewater. Recently Acidithiobacillus thiooxidans
and Acidithiobacillus ferroxidans are proved to be potent accumulators of
Fe3+ (4).
PATENTING IN THE FIELD OF BACTERIAL EPS

Bioactive microbial EPSs have shown enormous growth in patent-
ing from last 30 years as the first patent in “recombinant DNA plasmid
for xanthan gum synthesis” was published in 1987 by Merck. Till then
TABLE 1.2 Important Patents in the Field of Bacterial Exopolysaccharide in the

Last Two Years
Patent Filing Date Applicants Title
20150150959 06.04.2015 Children’s Medical Bacterial biofilm matrix as a
Center Corporation platform for protein delivery
20150079137 19.03.2015 Polymaris Exopolysaccharide for the
Biotechnology treatment and/or care of the skin,
mucous membranes, and/or nails
20140348878 27.11.2014 Ai et al. Strain of exopolysaccharide-
secreting Lactobacillus brevis and
application thereof
20140322273 30.10.2014 Ai et al. Strain of exopolysaccharide
secreting Lactobacillus plantarum
and application thereof
20140171386 19.06.2014 Cheuk et al. Method and composition to
reduce diarrhea in a companion
animal
20140057018 27.02.2014 Ashraf Hassan Processed cheese with cultured
dairy components and
manufacturing
20140037687 06.02.2014 Apariin et al. Exopolysaccharide of Shigella
sonnei bacteria, method for
producing same, vaccine and
pharmaceutical composition
containing same
20140037597 06.02.2014 Senni et al. Sulfated depolymerized derivatives
of exopolysaccharides (eps) from
mesophilic marine bacteria,
preparing same, and uses thereof
in tissue regeneration
Source: http://tgs.freshpatents.com/Exopolysaccharide-bx1.php
bacterial xanthan gum from Xanthomonas campestris have different pat-

ents with varying applications. Some of the recent patenting trends in last
2 years have excelled with lactic acid bacteria, soil inhabitants, and halo-
philes (Table 1.2). More research is needed in the field of EPS producing
thermophiles and psychrophiles, as EPS is produced in large quantities to
survive in extreme harsh environment. Hyaluronan because of its highly
hydrophilic nature is currently used in pharmaceutical industry and has
the highest market value of 1 billion US$ among all other bacterial EPSs,
which indicates a strong market demand for it. But the main hindrance in
using hyaluronan commercially is its high cost, which is around 100,000
US$. Other important bacterial exopolysaccharides like xanthan, gellan,
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however be of a different kind. The Muses, like other nymphs, were worshipped in
grottoes as guardian genii of fountains, and Pliny, Hist. Nat., XXXVI, 21, writes of
‘erosa saxa in aedificiis, quae musaea vocant, dependentia ad imaginem specus
arte reddendam,’ where the suggestion is of a rustic grotto like that in the Boboli
Gardens. Such grottoes, natural or artificial, might fittingly be decked with shells
and coloured stones and any bright inlay that offered itself. If incrustations of the
kind we call mosaic were actually met with in these haunts of the Muses, the work
might readily be called by a name suggestive of these same nymphs, and this might
be applied later on to tesselated work in general. There is however no proof, either
in Pliny or elsewhere, that what we call mosaic was actually so used, and it has
been questioned by more than one authority whether there is really any connection
between the word ‘mosaic,’ in its various forms, and the Muses. An oriental
derivation has even been suggested for the term.
Dr Albert Ilg, in an exceedingly learned paper on the subject in the Wiener
Quellenschriften, Neue Folge, V, 158 f., offered an entirely new explanation of the
word ‘mosaic,’ which he maintained had in its original sense nothing to do with
inlaid work at all, but rather with gilding. He connected it with a root ‘mus’ or
‘mos,’ with a sense of ‘beating’ or ‘grinding,’ and instanced the mediaeval Latin
term ‘mosnerium,’ which Ducange notices as equivalent to ‘molendinum,’ ‘mill.’
‘Musivum opus’ would refer on this view to the gilding process in which the gold is
ground to powder or beaten out; and Ilg affirmed ‘Musaicum im alten Sinne kann
nur eigentlich Vergoldung, nicht das moderne Mosaik, bezeichnen.’ If the word at
first meant ‘gilded work’ it would later on be extended to what we know as ‘mosaic,’
because of the use in mediaeval mosaics of the familiar gold background. The
argument of Dr Ilg is not convincing, and the question must be considered still
open. Theophilus, for example, Lib. II, c. 12, uses ‘musivum opus’ for inlaid work in
which there is no question of gold.
143. Possibly what we call ‘mother of pearl.’
144. See Note on ‘The Sassi, della Valle, and other Collections,’ etc., postea, p.
102 f. The mosaic here noticed is unfortunately lost. Lanciani, The Golden Days of
the Renaissance in Rome, 1906, p. 234, states that he has searched for it in vain.
145. See Note 5, ante, p. 27.
146. Mosaics made up of small cubes of coloured or gilded glass are abundant
in early Christian and Byzantine times, but were also used, though sparingly, by
the Romans from the time of Augustus downwards. See Pliny, Hist. Nat., XXXVI,
189, who fixes the time of their introduction.
147. Egg-shell mosaic. See Note, postea, p. 136.
148. See Chapters XV and XVI of the ‘Introduction’ to Painting. The pavement
of the cathedral of Siena exhibits a large collection of such mosaics in black and
white executed in different technical processes.
149. See Note on ‘Ideal Architecture’ at the close of the ‘Introduction’ to
Architecture, postea, p. 138.
150. That is, about 4½ inches.
151. About 15½ inches.
152. See note on ‘The Nature of Sculpture,’ at the close of the ‘Introduction’ to
Sculpture, postea, p. 179.
153. ‘Working from manner.’ Vasari refers here to what artists call ‘treatment,’
which is a process of analysis and grouping, applied to appearances in nature
where the eye sees at first little more than a confused medley of similar forms that
are perhaps constantly changing. Under such an aspect the hair as well as the folds
of drapery on the human figure presented themselves to the early Greek sculptor,
and it was a long time before he learned to handle them aright. In the case of the
hair he had no help in previous work, for in Egyptian statues it is often covered, or
is replaced by a formal wig, and in Assyrian art the hair is very severely though
finely conventionalized. It was not until the age of Pheidias that the Greeks learned
how to suggest the soft and ample masses of the hair, and at the same time to
subdivide these into the distinct curls or tresses, each one ‘solid,’ as Vasari
requires, but individually rendered with the minuter markings which suggest the
structure and ‘feel’ of the material. The Italians started of course with this
treatment or ‘manner’ already an established tradition founded on antique
practice. In the mediaeval sculpture of the thirteenth and fourteenth centuries in
France and England the hair is often very artistically rendered.
154. This paragraph opens up a subject of much artistic interest, on which see
Note on ‘Sculpture Treated for Position,’ at the close of the ‘Introduction’ to
Sculpture, postea, p. 180 f.
155. For Vasari, a practical artist, to commit himself to the statement that
figures are made nine heads high, is somewhat extraordinary, for eight heads, the
proportion given by Vitruvius (III, 1) is the extreme limit for a normal adult, and
very few Greek statues, let alone living persons, have heads so small. The recently
discovered ‘Agias’ by Lysippus, at Delphi, is very nearly eight heads high. The
‘Doryphorus’ at Naples not much more than seven. The ‘Choisseul Gouffier Apollo’
about seven and a half, etc. Vasari seems to have derived his curious mode of
reckoning from Filarete, who in Book 1 of his Treatise on Architecture measures a
man as follows: Head = 1 head, neck = ½, breast = 1, body = 2, thighs = 2, legs = 2,
foot = ½, total nine heads. Alberti, Leonardo, Albrecht Dürer, and indeed almost
all the older writers on art, discourse on the proportions of the human figure.
156. See Note on ‘Waxen Effigies and Medallions,’ at the close of the
‘Introduction’ to Sculpture, postea, p. 188.
157. One objection to an armature of wood is that the material may swell with
the damp of the clay and cause fissures. Iron is objectionable because the rust
discolours the clay. Modern sculptors often use gas-piping in the skeletons of their
models, as this is flexible and will neither rust nor swell.
158. Baked flour used to be employed by plasterers to keep the plaster they
were modelling from setting too rapidly. See the Introduction by G. F. Robinson to
Millar’s Plastering Plain and Decorative, London, 1897. The former used rye
dough with good effect for the above purpose.
159. The tow or hay tied round the wood affords a good hold for the clay,
which is apt to slip on anything smooth.
160. This method of producing drapery is not very artistic.
161. See Note on ‘Proportionate Enlargement’ at close of the ‘Introduction’ to
Sculpture, postea, p. 190.
162. See Note on ‘The Use of Full-sized Models’ at the close of the
‘Introduction’ to Sculpture, postea, p. 192.
163. The carvers’ tools described by Vasari are the same that appear to have
been in use in ancient Greece (see the article by Professor E. Gardner already
referred to), that are figured in the Encyclopédie of the eighteenth century, and are
now in use. Fig. 2, E to J, ante, p. 48, shows a set of them actually employed in a
stone carver’s workshop at Settignano near Florence.
164. Actual polish of the surface of a marble figure is to be avoided, as the
reflections from it where it catches the light destroy the delicacy of the effect of
light and shade. Greek marbles were not polished, save in some cases where the
aim seems to have been to imitate the appearance of shining bronze, but the
Greeks finished their marbles more smoothly than the sculptors of to-day, most of
whom prefer a ‘sensitive’ surface on which the marks of the last delicate chiselling
can be discerned. Michelangelo’s Dead Christ in the ‘Pietà’ of St. Peter’s, his most
finished piece of marble work, may almost be said to show polish, and Renaissance
marbles generally are quite as smoothly finished as antiques. In the case of
coloured marbles, used for surface decoration in plain panels, polish is of course
necessary in order that the colour and veining may appear, but it does not follow
from this that a self-coloured marble, carved into the similitude of a face or figure,
should be polished.
165. English terminology for the different kinds of reliefs, and for sculpture
generally, is very deficient, and many Italian terms are employed. It may be noted
that Vasari’s ‘half relief’ (mezzo rilievo) is the highest kind he mentions, and would
correspond to what is called in English ‘high relief.’
166. See Note on ‘Italian and Greek Reliefs,’ at the close of the ‘Introduction’
to Sculpture, postea, p. 196.
167. Donatello’s flat, or ‘stiacciati’ reliefs are deservedly famous. The difficulty
here is to convey the impression of solid form of three dimensions with the
slightest possible actual salience. The treatment of the torso of the Christ in the
marble ‘Pietà’ of the Victoria and Albert Museum is a good example.
168. The antique vessels of so-called ‘Arezzo’ ware are called Aretine vases.
Messer Giorgio was in duty bound to take some note of the ancient pottery of his
native city for it was from this that the Vasari derived their family name. According
to the family tree given in a note to the Life of an ancestor of the historian (Opere,
ed. Milanesi, II, 561), the family came from Cortona, and the first who settled in
Arezzo was the historian’s great-grandfather, one Lazzaro, an artist in ornamental
saddlery. He had a son, Giorgio, who practised the craft of the potter, and was
especially concerned with the old Roman Aretine vases the technique of which he
tried to reproduce. Hence he was called ‘Vasajo,’ ‘the vase maker,’ from which
came the family appellation Vasari.
This ancient Aretine ware ‘must be regarded as the Roman pottery par
excellence’ (Waters, History of Ancient Pottery, Lond., 1905, II, 480). It is
practically the same ware that is known by the popular but unscientific term
‘Samian,’ and consists in cups and bowls and dishes usually of a small size of a fine
red clay, ornamented with designs in low relief, produced by the aid of stamps or
moulds. It is these relief ornaments that Vasari had in his mind when he wrote the
words in the text. Arezzo is noticed by Pliny and other ancient writers as a great
centre for the fabrication of this sort of ware, and Vasari tells us how his
grandfather, Giorgio the ‘vasajo,’ discovered near the city some kilns of the ancient
potters and specimens of their work. Very good specimens of Aretine ware are to
be seen in the Museum at Arezzo, and the fabrique is represented in all important
collections of ancient pottery.
169. See Note on ‘The Processes of the Bronze Founder’ at the close of the
‘Introduction’ to Sculpture, postea, p. 199, which the reader who is unacquainted
with the subject, will find it useful to read forthwith. The best commentary on
Vasari’s and Cellini’s account of bronze casting is to be found in the French
Encyclopédie, where there is a description, with numerous illustrations, of the
casting in 1699 of Girardon’s great equestrian statue of Louis XIV, destined for the
Place Vendôme. It was claimed at the time to be the largest known single casting in
the world, and represents in their utmost elaboration the various processes
described by Vasari. Some of the illustrations are here reproduced, and will help to
render clearer the descriptions in the text.
170. Plate VII shows a section or two of a piece-mould round a portion of a
figure. It will be noticed that the pieces are so planned that they will all come away
easily from the model and not be held by any undercut projections. The small
pieces are then all enclosed in an outer shell divided into two halves, and called in
French ‘chape’ answering to the ‘cappa’ of Vasari’s text. Plate VIII, A, shows the
model of the Louis XIV statue as piece-moulded.
171. In the case of a heavy casting such an armature is necessary, and must be
carefully constructed to give support at all points. The armature within the core of
the horse of Louis XIV is shown in Plate VIII, D.
172. Vasari here describes a method of constructing the indispensable shell of
wax which is to be replaced by the bronze. The hollow piece-mould is lined section
by section with wax and a core is then formed to fill the rest of the interior and
touch the inner surface of the wax at every point. The plaster mould is then
removed and the wax linings of each of its sections are applied, each in its proper
place, to the core, and fixed thereon by skewers. There is then a complete figure in
wax, but, as this is made up of very many pieces, it has to be gone over carefully to
smooth over the joins and secure unity of surface. Cellini’s plan seems a better one.
He lines his hollow mould with a sort of paste or dough, and then fills up with the
core. The dough is then removed and wax is poured in in its place, thus forming a
continuous skin and securing a more perfect unity in the waxen shell.
173. On Plate VIII at B we see the core covered with the skin of wax and
carefully gone over and finished in every part. The system of pipes with which it is
covered are the ‘vents’ that Vasari notices in § 62, and also the channels through
which the melted wax is to escape and the molten bronze to enter, as noticed in §§
63, 64.
174. Vasari actually says that it must be put ‘al fuoco’ ‘to the fire,’ but it is clear
that he does not mean that heat is at once to be applied to it. If this were done the
wax would all be melted off the core too soon, before it was covered by the outer
skin. It is only when the wax has been securely enclosed between the core and the
outer skin that heat is needed to melt it away and leave its place free for the molten
metal.
175. Plate VIII, C, shows this outer armature, with the ends of the transverse
rods holding core and envelope together.
176. ‘Give passage to the metal.’ Their essential purpose is to allow for the
escape of air which would be dangerous if driven by the metal into a confined
space.
177. It should be understood that, in the process Vasari has in mind, the
melted metal is introduced at the bottom of the mould so as to rise in it and expel
before it the air. It is not poured in at the top. Hence the metal enters at the same
orifice at which the wax flows out.
178. Plate VIII, D, gives a section through the model in the casting-pit, when
all is ready for the actual operation of introducing the molten metal. The wax has
all been run out, and the outline of the figure and of the horse is marked by a
double line with a narrow space between. It is this space that will be filled by the
bronze which will be introduced through numerous channels so that it may be
distributed rapidly and evenly over the whole surface it is to cover. When in the pit
the mould is packed all round with broken bricks or similar material, so that ‘the
bronze may not strain it,’ nor cause it to shift.
179. The wax has already been carefully weighed, and in order to estimate how
much bronze will be required for the cast a rough calculation is made based on the
amount of wax.
180. The subject of the composition of bronze and of other alloys of copper is a
complicated one, for the mixtures specified or established by analysis are very
varied. Normally speaking, bronze is a mixture of copper with about ten per cent.
of tin, brass of copper with twenty to forty per cent. of zinc. Vasari’s proportions
for bells and for cannon are pretty much what are given now. In the Manuel de
Fondeur (Manuels Roret) Paris, 1879, II, p. 94, eight to fifteen per cent. of tin are
prescribed for cannon, fifteen to thirty per cent. for bell metal, the greater
percentage of tin with the copper resulting in a less tough but harder and so
sharper sounding metal. It will be noted however that for statuary metal Vasari
specifies a mixture not of copper and tin but of copper and brass, that is, copper
and zinc. Brass is composed of, say, twenty-five per cent. of zinc and seventy-five
per cent. of copper, so that a mixture of two thirds, or sixty-six per cent., of copper
with one third, or thirty-three per cent., of brass would work out to about ten parts
of zinc to ninety of copper, and this agrees with classical proportions. The Greeks
used tin for their bronzes, but various mysterious ingredients were supposed to be
mingled in to produce special alloys. The Romans used zinc, or rather zinciferous
ores such as calamine, with or in place of tin, and this is the tradition that Vasari
follows.
A recent analysis of the composition of the bronze doors at Hildesheim, dating
from 1015 A.D., gives about seventy-six parts copper, ten lead, eight tin, four zinc;
and of the ‘Bernward’ pillar ascribed to about the same date, seventy copper,
twenty-three tin, and five lead. These differences may surprise us, but metal
casting in those days was a matter of rule of thumb, and we may recall Cellini’s
account of his cramming all his household vessels of pewter into the melting pot to
make the metal flow for casting his ‘Perseus.’
181. Vasari’s account of the making of dies for medals and of the process of
striking these is clear, and agrees with the more elaborate directions contained in
the seventh and following chapters of Cellini’s Trattato dell’ Oreficeria. Cellini
however, unlike Vasari, was a practical medallist, and he goes more into detail. The
process employed was not the direct cutting of the matrices or dies with chisels,
nor, as gems are engraved, by the use of the wheel and emery (or diamond)
powder, but the stamping into them of the design required by main force, by
means of specially shaped hard steel punches on which different parts of the design
had been worked in relief. The steel of the matrix or die had of course to be
previously softened in the fire, or these punches would have made no impression
on it. When finished it was again hardened by tempering. It may be noticed that
the dies from which Greek coins were struck were to all appearance engraved as
gems were engraved by the direct use of cutting tools or tools that, like the wheel,
wore away the material with the aid of sand or emery.
The two matrices, or dies, for the obverse and reverse of the medal, being now
prepared, the medal is not immediately struck. In the case of the Greek coin a
bean-shaped piece, or a disk, of plain metal, usually of silver, called a ‘blank’ or
‘flan,’ was placed between the two dies and pressed into their hollows by a blow or
blows of the hammer, so that all that was engraved on them in intaglio came out on
the silver in relief. Vasari’s process is more elaborate. A sort of trial medal is first
struck from the matrices in a soft material such as lead or wax, and this trial medal
is reproduced by the ordinary process of casting in the gold or silver or bronze
which is to be the material of the final medal. This cast medal has of course the
general form required, but it is not sharp nor has it a fine surface. It is therefore
placed between the matrices and forcibly compressed so as to acquire all the finish
of detail and texture desired.
182. Plaster, or stucco, is sometimes regarded as an inferior material only to
be used when nothing better can be obtained. It should not however be judged
from the achievements of the domestic plasterer of to-day, who has to trust
sometimes to the wall-paper to keep his stuff from crumbling away. Plaster as used
by the ancients, and through a good part of the mediaeval and Renaissance periods
up to the eighteenth century, is a fine material, susceptible of very varied and
effective artistic treatment. It was made by the Greeks of so exquisite a quality that
it was equivalent to an artificial marble. It could be polished, so Vitruvius tells us,
till it would reflect the beholder’s face as in a mirror, and he describes how the
Roman connoisseurs of his time would actually cut out plain panels of Greek
stucco from old walls and frame them into the plaster work of their own rooms,
just as if they were slabs of precious marble. (De Architectura, VII, iii, 10.) Vitruvius
prescribes no fewer than six successive coats of plaster for a wall, each laid on
before the last is dry, the last coat being of white lime and finely powdered marble.
By the Villa Farnesina at Rome some Roman, or more probably Greek, plaster
decoration was discovered a few years ago that surpassed any work of the kind
elsewhere known. We find there the moulded or stamped ornament Vasari
describes, as well as figure compositions modelled by hand, while the plain
surfaces are in themselves a delight to the artistic eye.
Among the best and best known stucco work, in figures and ornaments, of the
later Italian Renaissance, may be ranked that at Fontainebleau by Primaticcio and
other artists from the peninsula who were invited thither by François I, for the
decoration of the ‘Galerie François I’ and the ‘Escalier du Roi.’
183. The composition of these two mucilages is given by Theophilus, in the
Schedula, Book one, chapter 17, and also by Cennini, Trattato, chapters 110–112.
Soft cheese from cows’ milk must, according to the earlier recipe, be shredded
finely into hot water and braised in a mortar to a paste. It must then be immersed
in cold water till it hardens, and then rubbed till it is quite smooth on a board and
afterwards mixed with quick lime to the consistency of a stiff paste. Panels
cemented with this, says Theophilus, will be held so fast when they are dry that
neither moisture nor heat will bring them apart. Vasari does not seem to have such
faith in the mucilage, and prefers that made from boiling down shreds of
parchment and other skins. The twelfth century writer knows how to make this
also. See chapter eighteen of the first Book of the Schedula.
184. Every museum contains examples of these delicate German carvings in
hard materials.
185. In a Note to the ‘Introduction’ to Architecture, ante, p. 128 f., an account
was given of some sculptures in travertine on the façade of the church of S. Luigi
dei Francesi at Rome by a ‘Maestro Gian’ who has been conjecturally identified as a
certain Jean Chavier or Chavenier of Rouen who worked at Rome in the first
quarter of the sixteenth century. Vasari in this place introduces an artist of the
name of ‘Maestro Janni francese,’ and the question at once arises whether he is the
same person as the ‘Maestro Gian’ of Rome.
The statue here described is to be seen in the church of the Annunziata at
Florence, but not where Vasari saw it. It has been placed for about the last half
century in the spacious round choir, where it occupies a niche in the wall of the
second chapel to the left as one faces the high altar. It has been painted white in
the hope that it may be mistaken for marble, and this characteristic performance
dates from about 1857. Certain fissures observable show however that it is of wood,
and one of the Frati remembers it when it was as Vasari saw it ‘nello stesso colore
del legname.’ The work is shown on Plate IX. We have been unable to discover
anything certain about the artist. The figure, which is in excellent preservation,
speaks for itself. The Saint has a tight fitting cap over his head and curling hair and
beard. His eyes are almost closed as he looks down with a somewhat affected air at
his wounded leg to which the finger of his right hand is pointing. The other hand
holds a staff, round which the drapery curls and over the top of which it is caught.
This drapery bears out Vasari’s description of it as ‘traforato’ ‘cut into.’ It is floridly
treated with the sharp angles common in the carving of the fifteenth and sixteenth
centuries in Germany, Flanders, and parts of France. M. Marcel Reymond, who has
kindly given his opinion on the photographs submitted to him, has written about it
as follows: ‘Le St. Roch, par la surcharge de vêtements, l’excès de reliefs, l’agitation
des draperies, se rattache à l’art français tel qu’il s’était constitué au xivme siècle, et
tel qu’il s’était continué jusqu’au xvime siècle, notamment dans le Bourgogne et la
Champagne.’ He does not consider the two ‘Maîtres Jean’ the same person. ‘Ce
sont sans doute deux artistes du xvime siècle, l’un travaillant la pierre, le travertin,
l’autre travaillant le bois. C’est leur aptitude à travailler ces deux matières, que les
artistes italiens travaillaient moins bien que les français qui a retenu l’attention de
Vasari sur eux et qui leur a fait attribuer une place si importante dans les préfaces
de Vasari.’ Our study of the originals at Rome and Florence has led us to the same
opinion. The S. Rocco is Gothic in feeling, the ‘Salamander’ and other pieces at
Rome are Renaissance. The Roman ‘Maestro Gian’ may be credited with an Italian
style, but Vasari does not show much critical acumen when he sees ‘la maniera
italiana’ in the S. Rocco of the Florentine Janni.
186. The first two sections, §§ 74, 75, of this chapter were added by Vasari in
the second edition. They contain his contribution to the philosophy of the graphic
art. It will be noted that his word ‘Disegno’ corresponds alike to our more general
word ‘design’ and the more special term ‘drawing.’
187. This remark of Vasari is significant of the change in architectural practice
between the mediaeval and modern epochs. That the architect is a man that sits at
home and makes drawings, while practical craftsmen carry them out, is to us a
familiar idea, but the notion would greatly have astonished the builders of the
French Gothic cathedrals or the Florentines of the fourteenth century. In
mediaeval practice the architect was the master of the work, carrying the scheme of
the whole in his head, but busy all the time with the actual materials and tools, and
directing progress rather from the scaffolding than from the drawing office. On the
tombstone of the French architect of the thirteenth century, Hughes Libergier, at
Reims, he is shown with the mason’s square, rule, and compasses about him; while
in the relief that illustrates ‘Building’ on Giotto’s Campanile at Florence we see the
master mason directing the operations of the journeymen from a position on the
structure itself. In the present day there is a strong feeling in the profession that
this separation of architect and craftsman, which dates from the later Renaissance,
is a bad thing for art, and that the designer should be in more intimate touch with
the materials and processes of building.
188. It is characteristically Florentine to regard painting as essentially the
filling up of outlines, and to colour in staccato fashion with an assorted set of tints
arranged in gradation. To the eye of the born painter outlines do not exist and
nature is seen in tone and colour, while colours are like the tones of a violin infinite
in gradation, not distinct like the notes of a piano. With the exception of the
Venetians and some other North Italians such as Correggio and Lotto, the Italians
generally painted by filling outlines with local tints graded as light, middle, and
dark, and the Florentines were pre-eminent in the emphasis they laid on the well-
drawn outline as the foundation of the art. Since the seventeenth century the
general idea of what constitutes the art of painting has suffered a change and
Vasari’s account of Florentine practice, in which he was himself an expert, is all the
more interesting. Vasari’s point of view is that of the frescoist. In that process,
which, as we shall see, had to be carried out swiftly and directly so as to be finished
at one sitting, it was practically necessary to have the various tints in their
gradations mixed and ready to hand. The whole method and genius of oil painting,
as moderns understand it, is different, and its processes much more varied and
subtle.
189. The innumerable sketches and finished drawings that have come down to
us from the hands of Florentine artists testify to the importance given in the school
to preliminary studies for painting, and any collection will furnish examples of the
different methods of execution here described. Drawings by Venetian masters, who
felt in colour rather than in form, are not so numerous or so elaborate.
190. That is to say, by observation of aerial as well as linear perspective.
191. This practice is noticed in the case of more than one artist of whom Vasari
has written the biography. Tintoretto is one. See also postea, p. 216.
192. See the Note on ‘Fresco Painting’ at the close of the ‘Introduction’ to
Painting, postea, p. 287.
193. Michelangelo’s greatest tour de force in foreshortening, much lauded by
Vasari in his Life of the master, is the figure of the prophet Jonah on the end wall
of the Sistine chapel. It is painted at the springing of the vault, on a surface that is
inclined sharply towards the spectator, but the figure is so drawn as to appear to be
leaning back in the opposite direction.
194. Correggio is responsible for many of the forced effects of drawing in the
decorative painting of vaults and ceilings in later times, but the Umbrian Melozzo
da Forlì in his painting of the Ascension of Christ, now destroyed save for the
fragments in the Quirinal and in the sacristy of St. Peter’s at Rome, may have the
doubtful honour of beginning the practice of foreshortening a whole composition,
so that the scene is painted as it would appear were we looking up at it from
underneath.
195. This truth, about the mutual influence of colours in juxtaposition, was
well put by Sir Charles Eastlake when he wrote, in his Materials for a History of
Oil Painting, ‘flesh is never more glowing than when opposed to blue, never more
pearly than when compared with red, never ruddier than in the neighbourhood of
green, never fairer than when contrasted with black, nor richer or deeper than
when opposed to white.’
196. Vitruvius describes the fresco process in his seventh Book. See Note on
‘Fresco Painting’ at the end of the ‘Introduction’ to Painting, postea, p. 287. This
chapter is one of the most interesting in the three ‘Introductions.’
197. Travertine, next to marble, makes when burnt the whitest lime (see § 30,
ante, p. 86). From this lime the fresco white, called bianco Sangiovanni, is made,
and Cennini gives the recipe for its preparation in his 58th chapter. The ordinary
lead white (biacca) cannot be used in fresco.
198. The word ‘tempera’ is used by Vasari and other writers as a noun
meaning (1) a substance mixed with another, as a medium with pigments (2) a
liquid in which hot steel is plunged to give it a particular molecular quality (ante, p.
30) (3) the quality thus given to the steel (ante, p. 32), while (4) it has come to
mean in modern times, as in the heading of this Note, a particular kind of painting.
It is really to be regarded as the imperative of the verb ‘temperare,’ which alike in
Latin and in Italian means ‘to divide or proportion duly,’ ‘to qualify by mixing,’ and
generally ‘to regulate’ or ‘to discipline.’ ‘Tempera’ thus means strictly ‘mix’ or
‘regulate.’ It is used in the latter sense in metallurgy, as the liquid which Vasari
calls (ante, p. 30) a ‘tempera’ (translated ‘tempering-bath’) regulates the amount of
hardness or elasticity required in the metal, and the quality the steel thus receives
is called (ante, p. 32) its ‘temper.’ In the case of painting the ‘tempera’ is the
binding material mixed with the pigment to secure its adhesion to the ground
when it is dry. The painting process is, in Italian, painting ‘a tempera’ ‘with a
mixture,’ and our expression ‘tempera painting’ is a loose one. For the form of the
word we may compare ‘recipe,’ also employed as a substantive but really an
imperative meaning ‘take.’
Strictly speaking any medium mixed with pigments makes the process one ‘a
tempera.’ Many substances may be thus used, some soluble in water, as size, gum,
honey, and the like; others insoluble in water, such as drying oils, varnishes, resins,
etc., while the inside of an egg which is in great part oleaginous may have a place
between. It is not the usage however to apply the term ‘tempera’ to drying oils or
varnishes, and a distinction is always made between ‘tempera painting’ and ‘oil
painting.’ See Note on ‘Tempera Painting,’ postea, p. 291.
199. This practice of covering wooden panels with linen and laying over this
the gesso painting ground was in use in ancient Egypt. In fact the methods
described by Cennini of preparing and grounding panels are almost exactly the
same as those used in ancient Egypt for painting wooden mummy-cases. Even the
practice, so much used in early Italian art, of modelling details and ornaments in
relief in gesso and gilding them, is common on the mummy-cases. On the subject
of gesso see Note 5 on p. 249.
200. Vasari’s expression ‘rosso dell’ uovo o tempera, la quale è questa’ calls
attention to the fact, to which his language generally bears testimony, that he
looked upon the yolk of egg medium as the tempera par excellence. When he uses
the term ‘tempera’ alone he has the egg medium in his mind, and the size medium
is something apart. See this chapter throughout.
201. Tempera painting has had a far longer history and more extensive use
than any other kind. The technique predominated for all kinds of painting among
the older Oriental peoples and in classical lands, and was in use both on walls and
on panels in Western Europe north of the Alps during the whole mediaeval period,
while south of the Alps and at Byzantium it was to a great extent superseded for
mural painting by fresco, but remained in fashion for panels till the end of the
fifteenth century. After the fifteenth century the oil medium, as Vasari remarks,
superseded it entirely for portable pictures, and partly for work on walls and
ceilings, but in our own time there has been a partial revival of the old technique.
See Note on ‘Tempera Painting,’ postea, p. 291.
The whole question of the different vehicles and methods used in painting at
various periods is a difficult and complicated one, and too often chemical analysis
fails to give satisfactory results owing to the small amount of material available for
experiment. Berger, in his Beiträge zur Entwicklungs-Geschichte der Maltechnik,
an unfinished work that has already run to a thousand pages, goes elaborately into
the subject, but has to admit that many points are still doubtful. It makes
comparatively little difference what particular medium is used in tempera
painting, but it is of great importance to decide whether a particular class of work
is in tempera or in fresco. In connection with this Berger has reopened the old
controversy as to the technique of Pompeian wall paintings, which have been
accepted as frescoes, on the authority of Otto Dönner, for a generation past. There
are difficulties about Pompeian work and it is well that the question has again been
raised, but Berger goes much too far when he attempts to deny to the ancients the
knowledge and use of the fresco process. The evidence on this point of Vitruvius is
quite decisive, as he, and Pliny after him, refer to the process of painting on wet
plaster in the most unmistakeable terms. See Note on ‘Fresco Painting, postea, p.
287.
202. This passage about the early painters of Flanders occurs just as it stands,
with some trifling verbal differences, in Vasari’s first edition of 1550. The best
commentary on it is, first, the account of the same artists in Guicciardini’s
Descrittione di Tutti i Paesi Bassi, first published at Antwerp in 1567, and next,
Vasari’s own notes on divers Flemish artists which he added at the end of the Lives
in the second edition of 1568 (Opere, ed. Milanesi, VII, 579 f.). He there made
certain additions and corrections from Guicciardini, the most noteworthy of which
is the mention of Hubert van Eyck, whom Vasari ignores in this passage of the
Introduction, but who is just referred to by Guicciardini at the end of his sentences
on the younger brother—‘A pari a pari di Giovanni andava Huberto suo fratello, il
quale viveva, e dipingeva continuamente sopra le medesime opere, insieme con
esso fratello.’ Vasari however in the notes of 1568 goes much farther than this, and,
though he does not call Hubert the elder brother, he seems to ascribe to him
personally the supposed ‘invention’—‘Huberto suo fratello, che nel 1510 (sic) mise
in luce l’ invenzione e modo di colorire a olio’ (Opere, l.c.). ‘John of Bruges’ is of
course Jan van Eyck. Vasari writes of him at the end of the Lives as ‘John Eyck of
Bruges.’ Vasari’s statement in this sentence is of great historical importance, for it
is the first affirmation of a definite ‘invention’ of oil painting, and the first
ascription of this invention to van Eyck. As van Eyck’s own epitaph makes no
mention of this, and as oil painting was practised long before his time, Vasari’s
statement has naturally been questioned, and on the subject the reader will find a
Note at the close of the ‘Introduction’ to Painting, postea, p. 294.
203. It was long supposed that this picture was the ‘Epiphany’ preserved
behind the High Altar of the Church of S. Barbara, Naples, but Crowe and
Cavalcaselle, History of Painting in North Italy, II, 103, pronounce this ‘a feeble
and injured picture of the eighteenth century.’
204. Frederick of Urbino (there were not two of the name as Vasari supposes)
seems to have had a bathroom decorated with secular compositions by the Flemish
master. Facio, whose tract De Viris Illustribus, written in the middle of the
fifteenth century, was printed at Florence in 1745, writes, p. 46, of ‘Joannes
Gallicus’ (who can be identified as Jan van Eyck) who had painted certain ‘picturae
nobiles’ then in the possession of Cardinal Octavianus, with ‘representations of fair
women only slightly veiled at the bath.’ Such pictures were considered suitable
decorations for bath chambers. There is a curious early example of mediaeval date
in the Schloss Runkelstein near Botzen in the Tyrol, in the form of wall paintings
round a bathroom on one side of which nude figures are seen preparing to enter
the water, while on two other walls spectators of both sexes are seen looking in
through an open arcade. The pictures here referred to by van Eyck are now lost,
but by a curious coincidence attention has just been directed to an existing copy of
one of them, of which Facio gives a special notice. The copy occurs in a painting by
Verhaecht of Antwerp, 1593–1637, that represents the picture gallery of an
Antwerp connoisseur at about the date 1615. There on the wall is seen hanging the
van Eyck, that corresponds closely to the full description given by Facio. The
painting by Verhaecht was shown at Burlington House in the Winter Exhibition,
1906–7, and in the ‘Toison d’Or’ Exhibition at Bruges in 1907. See also the
Burlington Magazine, February, 1907, p. 325. It may be added that the Cardinal
Octavianus mentioned above was a somewhat obscure prelate, who received the
purple from Gregory XII in 1408.
205. The latest editors of Vasari (Opere, ed. Milanesi, I, 184) think this may be
a picture in the Museum at Naples, ascribed there to an apocryphal artist
‘Colantonio del Fiore.’ Von Wurzbach says it is by a Neapolitan painter influenced
by the Flemings.
206. Roger van der Weyden, more properly called, as by Guicciardini and by
Vasari in 1568, ‘Roger of Brussels.’ In 1449 he made a journey to Italy, and stayed
for a time at Ferrara, which under the rule of the art-loving Este was very
hospitable to foreign craftsmen. He was in Rome in 1450 and may have visited
Florence and other centres. His own style in works subsequent to this journey
shows little of Italian influence.
207. Hans Memling. ‘No Flemish painter of note,’ remark Crowe and
Cavalcaselle, Early Flemish Painters, p. 256, ‘produced pictures more attractive to
the Italians than Memling.’ The Portinari, for whom Memling worked, were
Florentine merchants who had a house at Bruges, the commercial connection of
which with Tuscany was very close. In his Notes on Flemish Painters at the end of
the Lives, Vasari says that the subject of ‘a small picture in the possession of the
Duke’ which is probably the one here mentioned, was ‘The Passion of Christ.’ If
this be the case, it cannot be the beautiful little Memling now in the Uffizi, No. 703,
for the subject of this is ‘The Virgin and Child.’ It might possibly however be the
panel of ‘The Seven Griefs,’ a Passion picture in the Museum at Turin. On the other
hand, Passavant thought the Turin panel was the ‘Careggi’ picture that Vasari goes
on to mention. See Note on p. 268 of Crowe and Cavalcaselle’s work.
208. The German editors of Vasari identified Lodovico da Luano with the
well-known painter Dierich Bouts of Louvain, but the name Ludovico (Chlodwig,
‘Warrior of Renown’) is not the same etymologically as Dierich (Theodoric, ‘Prince
of the People’). It is to be noted that in Guicciardini we find a mention of ‘Dirich da
Louano,’ who is undoubtedly Dierich Bouts (the surname is derived from St.
Rombout the patron of Haarlem, where the painter, who is also called ‘Dirick van
Haarlem’ [see below], was born) and also a mention of Vasari’s ‘Ludovico da
Luvano.’ A scrutiny however of the sentence in Guicciardini, where the last-
mentioned name occurs, shows that it is copied almost verbatim from our text of
Vasari. (Vasari [1550]:—‘Similmente Lodovico da Luano & Pietro Christa, &
maestro Martino, & ancora Giusto da Guanto, che fece la tavola della comunione
de’l Duca d’ Vrbino, & altre pitture; & Vgo d’ Anuersa, che fe la tauola di Sancta
Maria Nuoua di Fiorenza’; Guicciardini:—‘Seguirono a mano a mano Lodouico da
Louano, Pietro Crista, Martino d’ Holanda, & Giusto da Guanto, che fece quella
nobil’ pittura della comunione al Duca d’ Vrbino, & dietro a lui venne Vgo d’
Anuersa, che fece la bellissima tauola, che si vede a Firenze in santa Maria nuoua’).
Vasari is accordingly responsible for this ‘Ludovico da Luano,’ whose name is duly
chronicled in von Wurzbach’s ‘Niederländisches Künstler-Lexicon, Leipzig, 1906,
II, p. 69, on the authority of Guicciardini alone, and who is called in M. Ruelens’s
annotations to the French edition of Crowe and Cavalcaselle ‘Louys de Louvain
(peintre encore inconnu).’ Subsequently Guicciardini mentions also a ‘Dirich d’
Harlem,’ who can be none other than the same Dierick Bouts, and Vasari, as a
return favour, copies back all three Diericks into his Notes at the end of the edition
of 1568. The first ‘Ludovico’ may be merely due to a mistake in the text of Vasari
carelessly adopted by Guicciardini. Vasari’s copyist may have written ‘Ludovico’ in
place of the somewhat similar ‘Teodorico.’ There was however a certain Ludovicus
Dalmau or Dalman (D’Alamagna?), a Flemish painter who worked at Barcelona in
Spain about 1445 (von Wurzbach, sub voce) who may be meant, though there is no
indication of a connection between him and Louvain.
209. Pietro Crista is of course Petrus Christus or Christi of Bruges, an imitator,
though as Mr Weale has shown not an actual pupil, of the van Eycks. Von
Wurzbach says that Guicciardini was the first to mention his name, but Vasari in
1550 already knows him. As an explanation of the surname it has been suggested
that the artist’s father may have had a reputation as a painter or carver of Christ-
figures, so that Petrus would be called ‘son of the Christ-man.’
210. The name Martin belongs to painters of two generations in Ghent, and
von Wurzbach thinks it is the earlier of these, Jan Martins, apparently a scholar of
the van Eycks, who is referred to here, and called by Guicciardini (see above), and
by Vasari in 1568, ‘Martino d’ Holanda.’ There was a later and better known Martin
of Ghent called ‘Nabor Martin.’ The more famous ‘Martins,’ ‘of Heemskerk,’ and
‘Schongauer,’ when referred to by Vasari, have more distinct indications of their
identity. See, e.g., Opere, V, 396.
211. Justus of Ghent worked at Urbino, where he finished the altar piece
referred to by Vasari in 1474. The ‘other pictures’ may be a series of panels painted
for the library at Urbino, on which Crowe and Cavalcaselle have an interesting
paragraph, op. cit. p. 180.
212. Hugo of Antwerp is Hugo van der Goes, whose altar piece painted for S.
Maria Nuova at Florence has now been placed in the Uffizi.
213. Vasari’s stories about the connection with oil painting of Antonello da
Messina, Domenico Veneziano, and Andrea dal Castagno have of course been
subjected to a good deal of hostile criticism. Those about the two latter artists are
in the meantime relegated to the limbo of fable, but the case of Antonello da
Messina is somewhat different, and we are not dependent in his case on Vasari
alone. He certainly did not visit Flanders in the lifetime of Jan van Eyck, for this
artist died before Antonello was born, but von Wurzbach accepts as authentic a
visit on his part to Flanders between 1465 and 1475, and sees evidence of what he
learned there in his extant works (Niederländisches Künstler-Lexicon, sub voce,
‘Antonello’).
214. ‘Terre da campane,’ ‘bell earths.’ There seem to be two possible meanings
for the phrase. It may refer to the material used for the moulds in bell casting, or to
the clay from which are made the little terra-cotta bells by which children in Italy
set great store on the occasion of the mid-summer festival. This last is improbable.
Baldinucci, Vocabolario del Disegno, sub voce ‘Nero di Terra di Campana,’
says that this is a colour made out of a certain scale that forms on moulds for
casting bells or cannon, and that it is good with oil, but does not stand in fresco.
Lomazzo also mentions the pigment.
215. ‘L’abbozza’ evidently refers to the first or underpainting, not to the sketch
in chalk, for in the first edition the passage has some additional words which make
this clear. They run as follows: ‘desegnando quella: e così ne primi colori l’abozza,
il che alcuni chiamono imporre.’
216. With the above may be compared ch. 9 of Book VII of L. B. Alberti’s De Re
Aedificatoria.
217. The matter in our § 87 was added in the edition of 1568. Though Vasari
declared so unhesitatingly for fresco as the finest of all processes of painting, he
tells us that he used oil for a portion of his mural work in the Palazzo Vecchio at
Florence, when he prepared it for the residence of Duke Cosimo, and we shall
notice later his praise of tempera (postea, p. 291). Vasari describes how he painted
in oil on the walls of a refectory at Naples (Opere, VII, 674), and gives us an
interesting notice of his experiments in the technique about the year 1540 at the
monastery of the Camaldoli, near Arezzo, where he says ‘feci esperimento di unire
il colorito a olio con quello (fresco) e riuscimmi assai acconciamente’ (Opere, VII,
667). The technique required proper working out, for it was not a traditional one.
The most notable instance of its employment before the end of the fifteenth
century is in the case of the ‘Last Supper’ by Leonardo da Vinci at Milan. A
commission of experts has recently been examining the remains of this, the most
famous mural painting in the world, and has ascertained that the original process
employed by Leonardo was not pure oil painting but a mixed process in which oil
played only a part. The result at any rate, as all the world is aware, was the speedy
ruin of the work, which now only tells as a design, there being but little of its
creator’s actual handiwork now visible.
Some words of the Report are of sufficient interest to be quoted. ‘Pur troppo,
dunque, la stessa tecnica del maestro aveva in sè il germe della rovina, ben presto,
infatti, avvertita nelle sue opere murali. Spirito indagitore, innovatore, voglioso
sempre di “provare e riprovare” egli voile abbandonare i vecchi, sicuri e
sperimentati sistemi, per tentare l’ esito di sostanze oleose in miscela coi colori.
Perchè nemmeno può dirsi ch’ ei dipingesse, in questo caso, semplicemente, ad
olio come avrebbe fatto ogni altro mortale entrato nell’ errore di seguire quel
metodo anche pei muri. Egli tentò invece cosa affato nuova; poichè, se da un lato
appaiono tracce di parziali e circoscritte arricciature in uso pel fresco, dall’ altro, la
presenza delle sostanze oleose è accertata dalla mancanza di adhesione dei colori
con la superficie del muro e dalle speciali screpolature della crosta o pelle formata
dai colori stessi, non che dal modo con quale il dipinto si è andato e si va
lentamente disgregando e sfaldando.’ Bollettino d’ Arte del Ministero della
Pubblica Istruzione, Roma, 1907, I, p. 17.
Another famous instance of the use of oil paint in mural work about a
generation later is to be found in the Sala di Costantino in the Vatican, where
Raphael’s pupils have left two of the decorative figures by the side of the Popes
executed in that medium. One (Urbanity) is close to the door leading to the Chapel
of Nicholas V, the other is on the wall containing the battle, and is in better
preservation than the first which is covered with wrinkles. The oil paint gives a
certain depth and richness of effect, but there is the fatal disadvantage that the
painting does not look a part of the wall as is the case with work done in fresco.
The fresco is really executed in the material of the ground, whereas oils and
varnishes have nothing in common with lime and earths, and the connection of
structure and decoration is broken. One of the most successful pieces of work of
the kind is the painting of ‘Christ at the Pillar’ by Sebastian del Piombo in S. Pietro
in Montorio at Rome. The work, which is executed on a cylindrical surface, is
rather shiny, an appearance which in mural painting is to be avoided, and it has
darkened somewhat, though this defect is not very apparent and the experiment
has on the whole succeeded well. Vasari’s Life of Fra Sebastiano contains a good
deal of information about this particular technique, which was essayed in the later
age of Italian painting more often than is sometimes imagined. It needs hardly to
be said that this oil painting on the actual plaster of the wall is a different thing
from the modern process of painting on canvas in the studio and then cementing
the completed picture on to the wall. Mural painting on canvas was introduced by
the Venetians in the fifteenth century, for at Venice atmospheric conditions seem
to have been unfavourable to the preservation of frescoes, and the Venetians
preferred canvas to plaster for their work in oils. It would be interesting to know
whether the canvas was ever fixed in situ before the painter commenced
operations, as from the point of view of the preservation of decorative effect this
would be of importance. Vasari’s story about Tintoretto’s proceedings at the Scuola
di S. Rocco (Opere, VI, 594) is evidence that canvases were painted at home and
put up on walls or ceilings when finished. Of course if a wall be covered with
canvas before the painting begins the canvas is to all intents and purposes the wall
itself, grounded in a certain way.
218. The use of canvas for the purpose in view was, as Vasari mentions below,
very common at Venice, where as early as about 1476, if we believe Vasari (Opere,
III, 156), Gentile Bellini executed in this technique the large scenic pictures with
which he adorned the Hall of Grand Council in the Ducal Palace. Such a process
would come naturally enough to Italian painters as well as to the Flemings, for they
had been accustomed from time immemorial to paint for temporary purposes on
banners and draperies, after a fashion of which Mantegna’s decorative frieze on
fine canvas at Hampton Court is a classic example. Canvas had however been
actually used for pictures even in ancient Egypt. Not only was the practice of
stretching linen over wooden panels to receive the painting ground in use there in
the time of the New Empire, but some of the recently discovered mummy-case
portraits from Egypt, of the earliest Christian centuries, are actually on canvas.
There is an example in the National Gallery. At Rome painting on canvas is
mentioned by Pliny (Hist. Nat., XXXV, 51) and Boethius (de Arithmetica, Praef., I)
says that ‘picturae ... lintea operosis elaborata textrinis ... materiam praestant.’ The
Netherland painters of the fifteenth century nearly always painted on panel, but
canvas was sometimes used, as by Roger van der Weyden in his paintings for the
Town Hall at Brussels.
219. Vasari prescribes ‘due o tre macinate’ of white lead for mixture with the
flour and nut oil for the priming of canvas. A ‘macinata’ was the amount placed at
one time on the ‘macina’ or stone for grinding colours. Berger suggests ‘handfuls’
as a translation, but the amount would be small, as for careful grinding only one or
two lumps of the pigment would be dealt with at one time.
220. The Ducal Palace, that adjoins S. Marco, is probably the building in
Vasari’s mind. The Library of S. Marco, Sansovino’s masterpiece, might also be
meant, as this was called sometimes the Palace of S. Marco. We must remember
however that, as noticed before, ante, p. 56, this building, at the time of Vasari’s
visit to Venice, was still unfinished.
221. On panels and canvases as used at Venice Vasari has an interesting note
at the beginning of his Life of Jacopo Bellini (Opere, III, 152). This was a subject
that would at once appeal to his practical mind when he visited the city. He notices
incidentally that the usual woods for panels were ‘oppio’ acer campestris, maple;
or ‘gattice,’ the populus alba of Horace, but that the Venetians used only fir from
the Alps. (Cennini, c. 113, recommends poplar or lime or willow. Pliny, Hist. Nat.,
XVI, 187, speaks of larch and box, and Ilg says that northern painters generally used
oak.) The Venetian preference for canvas, Vasari says, was due to the facts that it
did not split nor harbour worms, was portable, and could be obtained of the size
desired; this last he notes too in our text. Berger (Beiträge, IV, 29), gives the
meaning of ‘Grossartigkeit’ to the word ‘grandezza’ used above by Vasari, but of
course it only means material size, not ‘grandeur’ in an aesthetic sense.
222. See ‘Introduction’ to Architecture, § 13, ante, p. 54. The stone is a species
of slate. Slate is suitable for painting on. See Church’s Chemistry of Paints and
Painting, 1890, p. 21.
223. Greek paintings on marble panels have come down to us from various
periods of ancient art. Some early Attic specimens on tombstones are in the
museums of Athens, and at Herculaneum there was found an interesting painting
on marble of a group of Greek heroines playing at knuckle bones. A much earlier
slab with a figure of a warrior is in the Acropolis Museum at Athens.
224. These chiaroscuri or monochromes are characteristic of the later
Renaissance. They may either be frankly decorative, and in this form obey the rules
of all other pictorial enrichment; or they may have an illusive intention, and be
designed to produce the appearance on a flat wall of architectural members or
sculptured or cast-bronze reliefs. In this case, when on monumental buildings and
permanent, they are insincere and opposed to sound decorative principles, though
on temporary structures they are quite in place. Vasari was a famous adept at the
construction and adornment of such fabrics, which were in great demand for the
numerous Florentine pageants and processions. See his letters, passim.
225. There are examples of painted imitations of bronze in Michelangelo’s
frescoes on the vault of the Sistine. The medallions held by the pairs of decorative
figures of youths on the cornice are painted to represent reliefs in this metal.
Raphael’s Stanze and Loggie also furnish instances, and there are good examples
on the external façade of the Palazzo Ricci at Rome.
226. The clay or earth that Vasari speaks of forms the body of the ‘distemper’
or ‘gouache,’ as it would be called respectively in Britain and in France, and takes
the place of the ‘whitening’ used in modern times. Baldinucci in his Vocabolario
explains ‘Terra di cava o Terretta’ as ‘the earth (clay) with which vessels for the
table are made, that mixed with pounded charcoal is used by painters for
backgrounds and monochromes, and also for primings, and with a tempera of size
for the canvases with which are painted triumphal arches, perspectives, and the
like.’ It is of very fine and even texture, and Baldinucci says it was found near St.
Peter’s at Rome, and also in great quantity at Monte Spertoli, thirteen miles from
Florence.
227. This process of wetting the back of the canvas is to be noted. The chief
inconvenience of the kind of work here spoken of is that it dries very quickly, and
dries moreover very much lighter than when the work is wet. Hence it is an
advantage to keep the ground wet as long as possible till the tints are properly
fused, so that all may dry together. Wetting the back of the canvas secures this end.
The technique that Vasari is describing is the same as that of the modern theatrical
scene-painter, and would be called ‘distemper painting.’ The colours are mixed
with whitening, or finely-ground chalk, and tempered with size. The whitening
makes them opaque and gives them ‘body,’ but is also the cause of their drying
light. F. Lloyds, in his Practical Guide to Scene Painting and Painting in
Distemper, Lond. 1879, says (p. 42) ‘In the study of the art of distemper painting, a
source of considerable embarrassment to the inexperienced eye is that the colours
when wet present such a different appearance from what they do when dry.’
228. Does Vasari mean by ‘tempera’ yolk of egg? It has this sense with him
sometimes, as in the heading of chapter VI.
229. Cennini in his 67th chapter gives directions for preparing the mixed
colour he calls verdaccio. It was a compound of white, dark ochre, black and red.
230. The principle of sgraffito-work, that is the scratching through a thin
superimposed coat to bring to view an under layer of a different colour, seems to
have been established first in pottery making, and in this connection the Italians
called it ‘Sgraffiato.’ The adoption of the process for the decoration of surfaces of
plaster or cement was an innovation of the Renaissance, and Vasari appears to
have been the first writer who gives a recipe for it. According to his account in the
Lives, it was a friend of Morto da Feltro, the Florentine Andrea di Cosimo, who
first started the work, and Vasari describes the process he employed in phrases
that correspond with the wording of the present chapter (Opere, ed. Milanesi, V,
207). A modern expert describes the process as follows: ‘A wall is covered with a
layer of tinted plaster, and on this is superimposed a thin coating of white plaster.
The outer coat is scratched through, and the colour behind it is revealed. Then all
the white surface outside the design is cut away, and a cameo-like effect given to
the design. This is the art of Sgraffito as known to the Italian Renaissance’
(Transactions, R.I.B.A., 1889, p. 125). The process dropped out of use after a
while, but was revived in Germany in the middle of the nineteenth century, mainly
through the agency of the architect Gottfried Semper, the author of Der Stil. It is
sometimes used in our own country both on monumental and on domestic
buildings, and as it is simple and cheap and permanent it is well fitted for modern
use in our climate. The back of the Science School in Exhibition Road, S.
Kensington, was covered with sgraffiti by the pupils of the late F. W. Moody about
1872. They would be the better now for a cleansing with the modern steam-blast.
231. See the Notes on ‘Enriched Façades,’ and ‘Stucco “Grotesques,”’ at the
close of the ‘Introduction’ to Painting, postea, pp. 298, 299.
232. This passage presents some difficulty. It runs ‘Dunque, quelle che vanno
in campo bianco, non ci essendo il campo di stucco per non essere bianca la calce,
si dà per tutto sottilmente il campo di bianco.’ Vasari seems to have in his mind the
difference between ordinary plaster made, as he has just described, of ‘lime mixed
with sand in the ordinary fashion,’ which would not be white, and what he calls
‘stucco,’ by which term is probably meant the finer plaster made of white lime from
travertine and marble dust. Ordinary plaster has accordingly to be coated with
white before the work begins.
233. Examples of this whimsical style of decoration are abundant in the
Pompeian wall paintings, and the mind of Vitruvius was much exercised about
their frivolity and want of meaning (De Architectura, VII, v).
234. Vasari is not very clear in his account of these methods of work, but it is
enough to know that both by the ancients, and at the time of the Renaissance,
colour was used largely in connection with these reliefs, and the combination could
of course take several forms. In the loggia of the Villa Farnesina, where Raphael
worked with his assistants, there are painted panels in fresco framed in mouldings
of stucco, modelled plaster figures in white against a coloured ground, coloured
stuccoes against coloured fields, and tinted bands separating the framed plaster
medallions. The same kind of work is found in the Loggie of the Vatican, the Doria
Palace at Genoa, and other localities innumerable. Plate XII shows a characteristic
section of the decoration of the Vatican Loggie.
235. As in the work described at the close of ch. XII (the beginning of the
present section).
236. The word ‘bolus’ is derived from the Greek βῶλος, a lump or clod, and
means, according to Murray’s Dictionary, a pill, or a small rounded mass of any
substance, and also a kind of reddish clay or earth, used medically for its astringent
properties, that was brought from Armenia, and called by the pharmacologist ‘bole
armeniac.’ Its use in the arts is due to its unctuous character, which made gold
adhere to it. See below. In mediaeval illuminations a ‘bolus’ or small lump of a

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New and Future Developments in Microbial Biotechnology

Microbial Biotechnology Basic Research and Applications

Health Policy Analysis An Interdisciplinary Approach

The 2017 Gulf Crisis An Interdisciplinary Approach

An Interdisciplinary Approach for Disaster Resilience

Disability and Technology: An Interdisciplinary and

Integrated Water Resource Management: An

The Ethics of Silence An Interdisciplinary Case

No claim to original U.S. Government works

Printed on acid-free paper

International Standard Book Number-13: 978-1-4987-5677-8 (Hardback)

Chapter 1 ◾ Bacterial Exopolysaccharides: Major Types

Chapter 2 ◾ Bioremediation: A Novel Green Technology

Chapter 3 ◾ Recent Developments in Food Biotechnology

Chapter 4 ◾ Molecular Characterization and

Chapter 5 ◾ Thermostable Enzymes and Their Industrial

Chapter 6 ◾ Microbial Enzymes for Pulp and Paper

Chapter 7 ◾ Rhizobacteria: Tools for the Management

Chapter 8 ◾ Betulin Biotransformation toward Its

Chapter 9 ◾ Optimizing the Performance of Wastewater

Chapter 10 ◾ Production of Fructooligosaccharides as

Chapter 11 ◾ Avenues in Ophthalmic Optical Coherence

T he book Microbial Biotechnology: An Interdisciplinary Approach,

T he book describes the interdisciplinary scope of biotechnology

1. The book envisages the recent ideas of novel findings in microbiology.

This book will also act as an important means of information on research-

This book will be a valuable resource to senior undergraduate and grad-

Pratyoosh Shukla, PhD

Folasade Adeyemo Oluyemi Olatunji Awolusi

Rohan Chawla Shika Gupta

Nabin Kumar Dhal Vijai Kumar Gupta

Varun Gogia Santhosh Kumar

Jashan Gokal Sheena Kumari

Swati Sucharita Panda Anjali Singh

Pratyoosh Shukla Ruby Yadav

Aparna Banerjee and Rajib Bandopadhyay

Centrifugation of microbial culture

Precipitation of EPS using

Isolation of EPS from

Morphological Physical characterization Chemical

elodea and Sphingomonas paucimobilis, cellulose from Gluconacetobacter

EPS PRODUCING BACTERIA: MAJOR TYPES

Lactic Acid Bacteria

Bacterial Exopolysaccharides ◾ 5

Bacterial Exopolysaccharides ◾ 7

halophiles, and borderline halophiles. The halotolerant bacteria in con-

EPS from Pathogenic Bacteria

results in resistance to antimicrobial drugs, which is the root to many

REGULATION OF EPS PRODUCTION

Substrate (a) is first catabolized by glycolytic pathways into pyruvate

PRESENT STUDIES ON BACTERIAL EPS

NDP-sugars ATP ABC

EPS EPS Extracellular

FIGURE 1.2 Schematic diagram showing biosynthetic pathways of EPS syn-

and it has a glucose backbone with trisaccharide side chain of gluc-

of Lactobacillus Leuconostoc and Streptococcus. Substrate synthe-

FUTURE PROSPECTS OF BACTERIAL EPSs

Chapter 1 ◾ Bacterial Exopolysaccharides: Major Types

Chapter 2 ◾ Bioremediation: A Novel Green Technology

Chapter 3 ◾ Recent Developments in Food Biotechnology

Chapter 4 ◾ Molecular Characterization and

Chapter 5 ◾ Thermostable Enzymes and Their Industrial

Chapter 6 ◾ Microbial Enzymes for Pulp and Paper

Chapter 7 ◾ Rhizobacteria: Tools for the Management

Chapter 8 ◾ Betulin Biotransformation toward Its

Chapter 9 ◾ Optimizing the Performance of Wastewater

Chapter 10 ◾ Production of Fructooligosaccharides as

Chapter 11 ◾ Avenues in Ophthalmic Optical Coherence