Papers by Ragnar Johannsson
FEMS Microbiology Ecology, 2018
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Cellulose Chemistry and Technology, 2014
Increased demand of fish in combination with overexploitation of the fish stocks of the oceans ha... more Increased demand of fish in combination with overexploitation of the fish stocks of the oceans has led to an increased production of fish through aquaculture. Today, fishmeal is the main protein source in fish feed for most aquaculture species. However, fishmeal is soon expected to fall short of demand as its production is associated with environmental problems. This shortage must therefore be met by sustainable alternative protein sources. Protein-rich microorganisms (i.e. Single cell protein) is an interesting option as a fishmeal substitute in fish feed which, in addition, can be produced as an important co-product in wood-based biorefineries. In the current study, four different microorganisms were cultivated on five different residual streams from Swedish wood-based biorefineries. Screening experiments were carried out in shake flasks, optimization experiments in benchtop bioreactors, and scale-up experiments were performed in a 50-litre pilot bioreactor. In addition, a demo-sc...
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Hofundar: Guðjon Þorkelsson, Margret Geirsdottir, Ragnar Johannsson, Sigurður Hauksson, Sjofn Sig... more Hofundar: Guðjon Þorkelsson, Margret Geirsdottir, Ragnar Johannsson, Sigurður Hauksson, Sjofn Sigurgisladottir, Arnljotur Bjarki Bergsson
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Aquaculture Environment Interactions, 2019
Genetic interactions (i.e. hybridization) between wild and escaped Atlantic salmon Salmo salar fr... more Genetic interactions (i.e. hybridization) between wild and escaped Atlantic salmon Salmo salar from aquaculture operations have been widely documented, yet the ability to incorporate predictions of risk into aquaculture siting advice has been limited. Here we demonstrate a model-based approach to assessing these potential genetic interactions using a salmon aquaculture expansion scenario in southern Newfoundland as an example. We use an eco-genetic individual-based Atlantic salmon model (IBSEM) parameterized for southern Newfoundland populations, with regional environmental data and field-based estimates of survival, to explore how the proportion of escapees relative to the size of wild populations could potentially influence genetic and demographic changes in wild populations. Our simulations suggest that both demographic decline and genetic change are predicted when the percentage of escapees in a river relative to wild population size is equal to or exceeds 10% annually. The occu...
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Journal of Aquatic Food Product Technology, 2019
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Marine drugs, Jan 19, 2017
The marine genus Pseudoalteromonas is known for its versatile biotechnological potential with res... more The marine genus Pseudoalteromonas is known for its versatile biotechnological potential with respect to the production of antimicrobials and enzymes of industrial interest. We have sequenced the genomes of three Pseudoalteromonas sp. strains isolated from different deep sea sponges on the Illumina MiSeq platform. The isolates have been screened for various industrially important enzymes and comparative genomics has been applied to investigate potential relationships between the isolates and their host organisms, while comparing them to free-living Pseudoalteromonas spp. from shallow and deep sea environments. The genomes of the sponge associated Pseudoalteromonas strains contained much lower levels of potential eukaryotic-like proteins which are known to be enriched in symbiotic sponge associated microorganisms, than might be expected for true sponge symbionts. While all the Pseudoalteromonas shared a large distinct subset of genes, nonetheless the number of unique and accessory ge...
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Handbook of Seafood Quality, Safety and Health Applications, 2010
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Journal of Aquatic Food Product Technology, Apr 16, 2014
ABSTRACT The aim was to develop a Quality Index Method (QIM) scheme for fresh tilapia fillets and... more ABSTRACT The aim was to develop a Quality Index Method (QIM) scheme for fresh tilapia fillets and evaluate the scheme in a shelf life study. Farmed tilapia fillets were stored at 1 and −1°C for up to 20 days, and changes during storage were observed with sensory evaluation using the QIM scheme and General Descriptive Analysis (GDA), total viable counts (TVC), and hydrogen sulphide (H2S) producing bacteria. The maximum shelf life of fillets stored at1 and −1°C was determined with GDA and microbial counts as 16 and 19 days, respectively. A high correlation of R2 = 0.943 between Quality Index (QI) and storage time at 1C° was found to be 0.843 at −1°C. At the end of shelf life, the QI was 5.3 and 6.5 out of a maximum score of 15 for fillets stored at 1 and −1°C, respectively. Total viable counts and H2S-producing bacteria showed an increasing trend during storage time for both groups. At the end of shelf life, TVC was log 7 cfu/g in the flesh of both groups, with H2S producing bacteria constituting a higher proportion (log 6 cfu/g) of the total. The scheme was modified at the end of the study to better characterize deskinned farmed tilapia fillets.
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... Concentration and purification by ultrafiltration of marine peptides solutions. L. Vandanjon,... more ... Concentration and purification by ultrafiltration of marine peptides solutions. L. Vandanjon, R. Johannsson, M. Derouiniot, P. Jaouen, Patrick Bourseau 1. (2007). ... Contributeur : Noluenn Chauvin <>. Soumis le : Jeudi 2 Juillet 2009, 12:01:32. ...
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Cited By (since 1996):3, Export Date: 18 October 2014
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Disclaimer: This is a version of an unedited manuscript that has been accepted for publication. A... more Disclaimer: This is a version of an unedited manuscript that has been accepted for publication. As a service to authors and researchers we are providing this version of the accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proof will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to this version also. PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the "Content") contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and...
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Inngangur Í erindinu er reynt að svara því hvernig líftaekni muni gagnast íslenskum matvaelaiðnað... more Inngangur Í erindinu er reynt að svara því hvernig líftaekni muni gagnast íslenskum matvaelaiðnaði tengdum landbúnaði. Segja má að líftaeknin geti komið við sögu á tveimur meginsviðum – Annars vegar erfðataekni til nota við kynbaetur og svo hins vegar nýting líftaeknilegra afurða sem ég kýs að kalla svo. Þar er um að raeða ensím sem nýtast á marga lund við að baeta gaeði ýmissa landbúnaðarafurða. Þessi ensím – koma oft frá hitakaerum örverum sem lifa í vatns-og leirhverum. Erfðafraeði: Margvíslegar erfðataekniaðferðir, sem þróaðar hafa verið til nota í mannerfðafraeði við leit að meingenum eru nú í vaxandi maeli notaðar til að hraða markvissum kynbótum í búfénaði. Búfjárkyn bera í sér svipgerðartengdan erfðabreytileika, sem hefur markvisst hefur verið valið fyrir í kynbótum. Áhugi er á að greina flestar þessara arfgerða og kanna lífefna-og lífeðlisfraeði þeirra. Í framhaldi af því er haegt að beita erfðamarkatengdu vali (MAS – Marker assisted selection) Í búfénaði er sérstakur áhugi...
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Papers by Ragnar Johannsson