DE10222214A1 - Laboratory culture reactor for phototrophic organisms such as algae is fabricated from translucent material and sub-divided into two or more compartments - Google Patents

Abstract

A laboratory photo-bioreactor (1) acting as a culture chamber for phototrophic organisms requiring continued exposure to light, is new. The reactor (1) is especially sub-divided into two or more compartments containing the phototrophic organisms in conditions of light conducive to the culture growth. A laboratory photo-bioreactor (1) acting as a culture chamber for phototrophic organisms requiring continued exposure to light, is new. The reactor (1) is especially sub-divided into two or more compartments containing the phototrophic organisms in conditions of light conducive to the culture growth. Each compartment has a horizontal depth of 5 - 30 mm and is fabricated of translucent material e.g. artificial glass, glass or foil. The photo-bioreactor has an inlets for gas and fluid media, and means by which the biomass culture can be removed as required. The rear wall (2a) of the compartment (2) is made of a strong material. The compartment is platform shaped or tubular and facilitates continued production of a suitable culture in which the biomass concentration is determined by the dilution rate. Cells from the cells enjoying the highest exposure to incident light are discharged to compartments with lesser exposure.

Description

The invention relates to a photobioreactor and a Process for the production of biomass.

Photobioreactors are bioreactors in which phototrophic microorganisms such as algae, cyanobacteria and Purple bacteria are cultivated. In these reactors will either grow and multiply this Allows cells or the production of different Substances using phototrophic cells. Such Photobioreactors are sufficient in the literature (Hu, Q., N. Kurano, M. Kawachi, I. Iwasaki and S. Miyachi (1998): "Ultrahigh-cell-density culture of a marine green alga Chlorococcum littorale in a flatplate photobioreactor "." Appl. Microbiol. Biotechnol. " 49: 655-662; Zhang, K., N. Kurano and S. Miyachi (1999): "Outdoor culture of a cyanobacterium with a vertical flat plate photobioreactor: effects on productivity of the reactor orientation, distance settings between the plates, and culture temperature "." Appl. Microbiol. Biotechnol. ", 52: 781-786; Grobbelaar, J.U., L. Nedbal, L. Tichy and I. Setlik (1995): "Variations in some photosynthetic characteristics of microalgae cultured in outdoor thin-layered sloping reactors "." J. Appl. Phycol. " 7: 243-260; Degen, J. Ueblee, A., Retze. A., Schmid- Staiger, U., Trösch, W. (2001): "A novel airlift photobioreactor with baffles for improved light utilization through the flashing light effect "." J. Biotechnol. ", 92: 89-94; Lee, Y.K., Ding, S.Y., Low, C.S., Chang, Y.C., Forday, W.L., Chew P.C. (1995): "Design and performance of an α-tubular photobioreactor for mass cultivation of microalgae "." J. appl. Phycol. ", 7: 47-51; Pulz, O., Gerbsch, N., Bacholz, R. (1995): "Light energy supply in plate-type and light diffusing optical fiber bioreactors "." J. appl. Phycol. "7: 145-149; Richmond, A., Cheng- Wu, Z. (2001): "Optimization of a flat plate glass reactor for mass production of Nannochloropsis sp. Outdoors "." J. Biotechnol. ", 85: 259-269; Tredici, M.R., Materassi, R. (1992): "From open ponds to vertical alveolar panels: the Italian experience in the development of a reactor for the mass cultivation of photoautotrophic microorganisms "." J. appl. Phycol. "4: 221-231).

An important area of application for photobioreactors is the generation of algae, which play a role in the primary production of biomass. Algae are important CO ₂ consumers and can therefore be environmentally friendly. The algae include the prokaryotic cyanobacteria as well as the eukaryotic, microscopic algae classes. These organisms provide a variety of classes of substances that can be used for pharmaceutical, cosmetic, food, animal nutrition and technical purposes. Important classes of substances are lipophilic compounds, such as. B. fatty acids, lipids, sterols and carotenoids, hydrophilic substances such as polysaccharides, proteins or amino acids and phycobiliproteins and the total mass as a protein-rich, low-nucleic acid raw material.

The economy of microalgae produced substances is initially due to the productivity of the selected algae species determined. However, only if at the same time a high conversion efficiency of solar radiation energy in the desired biomass form is achieved and the energy expenditure and the Production, installation and operation costs of the System can be kept extremely low. A high Biomass productivity is dependent on the optimal light distribution in the Depending on the photobioreactor.

An important role in terms of optimal Light distribution and light use also play the ability of algae, different light intensities adapt. With this photo acclimatization one can distinguish between algae that are strong Light intensities are adjusted below in the Abbreviation "HL" (high light) summarized, and algae that are adapted to weak light intensities, in following under the designation "LL" (low light) summarized.

• - hohe, maximale Photosyntheseraten
• - geringer Anteil an Chlorophyll pro Biomasse
• - hoher Anteil an accessorischen Pigmenten, wie z. B. Carotinoiden
• - geringe Photosynthese-Effizienz
• - hohe I_k-Werte (Übergang zwischen lichtabhängiger und lichtgesättigter Photosynthese).

HL algae have the following properties:

• - high, maximum photosynthesis rates
• - low proportion of chlorophyll per biomass
• - high proportion of accessory pigments, such as B. Carotenoids
• - low photosynthesis efficiency
• - high I _k values (transition between light-dependent and light-saturated photosynthesis).

• - geringe, maximale Photosyntheseraten
• - hoher Anteil an Chlorophyll pro Biomasse
• - geringer Anteil an accessorischen Pigmenten, wie z. B. Carotinoiden
• - hohe Photosynthese-Effizienz
• - geringe I_k Werte.

LL algae, on the other hand, have the following properties:

• - low, maximum photosynthesis rates
• - high proportion of chlorophyll per biomass
• - low proportion of accessory pigments, such as. B. Carotenoids
• - high photosynthesis efficiency
• - low I _k values.

For the use of the previously known photobioreactors means this adaptation of the algae to the Light intensity the following: In the initial phase of cultivation in the field there is a low cell density per volume in front. The cells are average light intensity and thereby adapt HL status. With increasing growth the Cell density, and the average light intensity decreases due to the self-shadowing of the cells. The cells thus adapt to the LL state. This means that at the beginning of cultivation high Light intensities can be used and in the course of further cultivation only the lesser Light intensity, but never the entire area of Light intensity, d. H. high, medium and low Light intensities.

All photobioreactors known so far have in common that only the average light intensity is used can be. This average light intensity is particularly of the absorption of the biomass and partly from the light absorption of the culture medium dependent. In most cases, the Self-shadowing of the biomass, the available light intensity, so that with increasing biomass there is always a decrease the light intensity and thus a reduction in actually possible light output is connected.

It is therefore an object of the invention to To create a photobioreactor and a process which which no longer has the disadvantages described above having.

Starting from the preamble of claim 1 Task solved according to the invention, with in the characterizing Features specified in claim 1. Farther the task, starting from the generic term of Claim 10, solved according to the invention, with the characterizing part of claim 10 specified Features.

The invention relates to a photobiorector, which in is divided into several compartments, in which the the prevailing lighting conditions (Light intensity, wavelength spectrum) adapted, phototrophic organisms. In the compartment, which is the closest to the light, in hereinafter referred to as the front compartment, and therefore the the highest light intensity prevails HL-state cells. In the arranged behind Compartments are the cells that make up the have adjusted decreasing light intensity and thus in the state of medium light intensity to low Light intensity, LL state.

With the photobioreactor according to the invention and the It is now possible to process a large area of the Wavelength spectrum as well as the entire range of radiated light intensity with the highest possible Effectiveness to use photosynthetically. With the photobioreactor according to the invention and the method can Ability of the algae to adapt to light are, so that higher yields, based on the exposed area compared to known photobioreactors and procedures can be achieved. The productivity can compared to previously known photobioreactors and Procedures can be significantly increased. The front Compartment, with the cells in the HL state, passing through the inventive method also constant in this Condition can be maintained, the high light intensity use effectively. The compartments behind it, in which the light intensity decreases more and more, Due to their adjustment d. H. in that they increasingly have the properties of LL cells and this state by the method according to the invention is kept constant, even this lower one Use light intensity with high efficiency. Through the Linking the use of HL cells in combination with LL cells can be put together in a photobioreactor both strong, medium and low Light intensities in parallel with the maximum Photosynthesis rate can be used. This is the case with previously known Reactors not possible. Here the high Light intensity can only be used at the beginning of cultivation, being low in photosynthesis efficiency due to the low proportion of chlorophyll per biomass is present. Part of the light intensity remains unused. With increasing growth the decreases Light intensity in the reactor due to the self-shadowing of the Cells. There are only low light intensities used; high intensities remain unused.

Advantageous further developments are in the Subclaims specified.

The drawings show an example Embodiment of the photobioreactor according to the invention and the Process.

It shows:

Fig. 1 photobioreactor with the different compartments,

Fig. 3 photobioreactor with used for the cultivation facilities,

Fig. 3 photosynthetic rate as a function of the light intensity 2 hours after incubation,

Fig. 4 photosynthesis rate depending on the light intensity, 48 hours after incubation.

Fig. 1 shows the photobioreactor 1 with the compartments. 2 The front compartment A is irradiated directly with the wavelength spectrum of the light source, while the compartments B and C arranged behind it are irradiated only with light of the wavelength which is transmitted through the respectively arranged compartment. The rear wall 2 a of the last compartment C is constructed from opaque material.

Fig. 2 shows the photobioreactor 1 having two compartments 2. The front compartment A, which is irradiated directly by the light source and in which there are consequently cells in the HL state, is supplied with nutrient solution from the storage vessel 3 via a peristaltic pump 4 . The suspension from compartment A is transferred into compartment B by means of a metering pump 5 . From there, the product (biomass) can be collected in a collecting container 6 .

Fig. 3 shows experimental results of the rate of photosynthesis, which with the inventive photobioreactor (reactor I) and a reactor with only one compartment is (Reactor II) a short time after incubation (2 h) were determined. The abscissa X represents the light intensity in µmol quanta m ^-2 s ^-1 . The ordinate Y indicates the photosynthesis rate as oxygen production in µmol O ₂ per mg Chl a and h. The measured values shown with a black, filled circle were determined from reactor I compartment A. The measured values shown with a circle not filled in were determined from reactor I compartment B. The measured values shown with a black filled triangle were determined from reactor II.

Fig. 4 shows experimental results of the rate of photosynthesis, which with the inventive photobioreactor (reactor I) and a reactor with only one compartment (Reactor II) for 48 hours were obtained after incubation. The axis labeling and marking of the measurement results correspond to those from FIG. 3.

The invention is intended to serve as an example below to be discribed.

The nutrient medium is introduced into the photobioreactor 1 according to the invention, which consists of several compartments 2 connected in series, and inoculated with the desired phototrophic organism which is to be cultivated. The photobiorector 1 comprises at least two compartments 2 . However, 3 to 8 compartments are also suitable. Three compartments have proven to be particularly suitable.

The term compartment 2 is to be understood in each case as part of the photobioreactor which contains the phototrophic organisms which have adapted to the prevailing light conditions in the respective compartment 2 , such as the light intensity and the light spectrum. This means, for example, that cells in the front compartment A, in which the highest light intensity and almost the entire wavelength spectrum of the light source are present, are in the HL state. With increasing distance of the compartments from the light source, the light intensity and also the wavelength spectrum of the incident light decrease depending on the absorption of the phototrophic organisms and the material from which the compartments were made. In these compartments, the cells adapt to the LL state.

High light intensities mean a range from 1000 to 2000 µmol quanta m ^-2 s ^-1 , mean light intensities a range from 300 to 1000 µmol quanta m ^-2 s ^-1 and low light intensities a range from 0 to 300 µmol -Quants m ^-2 s ^-1 .

For an optimal cultivation and light supply of the phototrophic organisms in the compartments 2 , the depth (t) of the compartments 2 also plays a role. A depth of 5 to 30 mm per compartment has proven to be suitable. A depth of 15 to 20 mm is particularly preferred. The total depth of the photobioreactor 1 should be in a range of at least 10 mm to 20 cm. The term total depth is to be understood as the depth which is composed of the depth of all compartments 2 .

The photobioreactor 1 with its compartments 2 consists predominantly of translucent or transparent material, such as. B. glass, synthetic glass or in a particularly inexpensive variant made of foils. Only the rear wall 2 a of the rearmost compartment 2 should consist of stabilizing material, which can not give off any toxic substances for the organisms and has no corrosive properties, such as, for. B. steel, concrete, plastic. In an advantageous embodiment of the device, the rear wall 2 a of the respective compartment 2 can be equipped with cooling, or the individual compartments 2 are separated from one another by an intermediate space which enables a circulation of cooling air or coolant. In an advantageous embodiment of the photobioreactor 1 , the compartments 2 have a plate-like geometry. In a further advantageous embodiment of the photobioreactor 1 , it can also be tubular. The tubular compartments can be pushed into one another. The light source can be arranged outside the reactor, so that the cells are in the HL state in the outermost tube (compartment), and the cells adapt more and more to the LL state in the direction of the innermost tube (compartment). The light source can also be arranged inside the photobioreactor 1 , so that the cells of the innermost tube are in the HL state and the cells of the outer tube adapt to the LL state.

As phototrophic organisms that are cultivated can are all known organisms that are also used for Production of biomass and products from the field of Cosmetics, food industry and pharmacy be used, suitable. This includes all red, green and brown algae, such as chlorella, Dunaliella, Spirulina, Haematococcus, Synechocystis, Microcystis, Scenedesmus, as well as phototrophic bacteria, like the Rhodospirillineae and Chlorobiineae. Under Outdoor conditions, under certain conditions, Climatic conditions may be beneficial to thermophilic strains use phototrophic organisms. Under phototrophic Organisms are intended within the scope of the present invention also understood plant cell cultures become.

The phototrophic organisms are preferably cultivated in a continuous process. The biomass concentration is controlled by the dilution rate (flow rate ml h ^-1 / volume L) or the regulated supply of nutrient solution or cultivation medium (turbidostat). The biomass concentration in the rear compartments, e.g. B. B and C depends on the biomass concentration in the front compartment A. Part of the suspension of organisms from the front compartment A, coordinated with the biomass concentration, is introduced into the next compartment B arranged behind it. From this part of the suspension of the organisms, controlled by the biomass concentration, can then be passed into the next compartment C until the last compartment is reached. Thus, within the respective compartments 2, the state of the phototrophic organisms can always be kept constant with regard to light adaptation in accordance with the respective lighting conditions, without being due to e.g. B. increasing biomass change the lighting conditions in compartments 2 . By controlling the biomass concentration via the dilution rate, fluctuations in the biomass concentration due to different lighting conditions in the field can also be compensated for. However, a batch process and fed-batch process are also possible. The photobioreactor 1 has devices for introducing gas, such as. B. CO ₂ , air, N ₂ and facilities for the removal of the biomass produced and for controlling the cultivation process, such as. B. Circulation pumps, thermostats, flow meters, opacimeters.

In an advantageous embodiment of the photobioreactor according to the invention, the individual compartments 2 are designed as an airlift reactor, in which a liquid circulation within a constructively defined loop is generated by the introduction of air.

In the photobioreactor 1 , not only a single type of phototrophic organism, but also several different types of these organisms can be used simultaneously in the respective compartments. It is advantageous to arrange the phototrophic organisms which have a specific absorption spectrum in the compartment which is irradiated by light of the wavelength, which corresponds to the absorption spectrum of these organisms. For example, an algae that has its absorption maximum in the wavelength range from 600 to 700 nm, such as. B. Dunaliella, can be cultivated behind an algae that has its absorption maximum in the wavelength range from 400 to 600 nm, such as. B. Spirulina. In this case, the algae from the compartments would not be mixed. The photobioreactor 1 according to the invention is also suitable, for example, for the targeted production of carotenoids. For this purpose, the organisms are first cultivated in a compartment in which they adapt to the LL state (e.g. compartment B). Then they are transferred to the front compartment A, which, due to the strong light intensity, stimulates them to produce more carotenoids. So z. B. Dunaliella are first cultivated in a compartment in which medium to low light intensities predominate and the cells can adapt to the LL state. The culture medium required for growing the biomass contains nitrogen in order to achieve a high biomass concentration. Under these cultivation conditions, Dunaliella assumes the "green form", ie it has a clear, visible chloroplast that stains the cells green. The cells are harvested and transferred to a nitrogen-free medium. Then they are transferred to the front compartment A, where they are exposed to high light intensities. In response to the high light intensity, the cells form carotenoids to an increased extent, so that the "red shape" is formed. The cells are preferably fed to the front compartment A only in the cell concentration in which there is no self-shadowing of the cells from one another and as a result all cells are in the HL state in order to produce as much carotenoids as possible. By using a nitrogen-free medium, there can be no growth and thus an increase in biomass within the front compartment. The biomass that was generated in the rear compartments is preferably used.

embodiment Biomass production from Synechocystis in photobioreactor according to the invention compared to the production in a reactor without compartments

A thermophilic strain from Synecocystis was used to produce biomass. The SWOT medium was used as the nutrient medium (Zhang, KN Kurano, Miyachi, S. (1999): "Outdoor culture of a cyanobacterium with a vertical flat late photobioreactor: effects on productivity of the reactor orientation, distance settings beween the plates and culture temperature "." Appl. Microbiol. Biotechnol. ", 52: 781-786). The nutrient medium was enriched with CO ₂ (0.43 V / V) and heated to 40 ° C in a water bath. A fluorescent lamp with a high light intensity, which emits plant light and is usually used in greenhouses, was used as the light source, so that a light intensity of 280 μmol quanta m ^-2 s ^{-1 was} set on the front of the photobioreactors. The photobioreactor was constructed from 5 mm thick synthetic glass plates. The photobioreactor I according to the invention had the following dimensions:
Compartment A: 500 (H) × 150 (W) × 10 (D) mm with H = height; B = width and T = depth of the reactor.
Compartment W: 500 (H) × 150 (W) × 20 (D) mm.

The comparative reactor II consisted of only one compartment and had the following dimensions: 500 (H) × 150 (W) × 30 (D) mm. One side of Reactor II had a double layer of the artificial glass so that the light conditions within the two reactors were the same. Both reactors were filled with nutrient solution up to a height of 450 mm, so that a culture volume of 2.25 L resulted. In reactor I, compartment A contained 0.75 L and compartment B 1.5 L. The cultivation was carried out continuously in both reactors. A flow rate of 78 ml h ^-1 or 1872 ml d ^{-1 was} set. In compartment A of reactor I this corresponded to a retention time of 0.401 d ^-1 and in compartment B a retention time of 0.801 d ^-1 . Reactor II had a retention time of 1.202 d ^-1 . The suspension of organisms from compartment A was transferred to compartment B using a peristaltic pump. The volume in the reactors was kept constant by an overflow. The optical density was determined photometrically at a wavelength of 720 nm, an optical density of 1 corresponding to a dry biomass of 0.279 g L ^-1 . The chlorophyll a content was determined by absorbance measurements of a suspension of the organisms extracted in acetone at 664 and 647 nm.

To determine the photosynthesis rate, the oxygen production rate was examined in a "Rank Brothers" oxygen chamber at different light intensities. The different light intensities (µmol quanta m ^-2 s ^-1 ) were set using a slide projector and different filters. The photosynthesis rate (µmol O ₂ mg Chl a ^-1 h ^-1 ), determined by the amount of oxygen formed per Chl a and time, was plotted against the light intensity.

The area-specific productivity of the reactors was calculated from the biomass formed and the Flow rate of the reactor, based on the exposed Area of the photobioreactor.

Two hours after incubation, the algae in compartments A and B of reactor 1 and in reactor 2 still show a similar photosynthesis rate depending on the light intensity ( FIG. 3). 48 hours after incubation, the photosynthetic behavior was different. The cells from compartment A have characteristics of HL-adapted cells. The cells in compartment B and in reactor II have characteristics of cells of the LL state. The cells in compartment B are even more adapted to the LL state than the cells in reactor II, since the cells in reactor II are irradiated with the entire wavelength spectrum of the light source, while in compartment B the cells are only exposed to the residual light which compartment A passes through, are irradiated.

Table 1 shows the different, volumetric productivities of the two reactor types. Table 1 Bio-dry matter in compartments A and B of reactor I and in reactor II; a and b represent test series under the same conditions

The area-specific productivity of the reactor I was 47.98 gm ^-2 d ^-1 , while for the reactor II it was only 36.66 gm ^-2 d ^-1 . Compared to the reactor type with only one compartment, a significant increase in productivity of more than 30% was therefore achieved.

For an industrial application, it is necessary to scale up the photobioreactor. Here it is conceivable to construct photobioreactors with compartments in a size range of 2 m in height, 5 m in length and a total depth of approx. 10 cm. The photobioreactor should always be optimally aligned with the light, so that e.g. B. in the field the photobioreactor can track the position of the sun. The photobioreactor according to the invention and the method are particularly suitable for the production of high biomass concentrations with maximum yield. This is important, for example, in the production of biomass for the provision of bioenergy, the extraction of fine chemicals from the biomass, processes for CO ₂ absorption and wastewater treatment.

Claims (15)

1. photobioreactor ( 1 ), characterized in that it comprises a plurality of compartments ( 2 ) in which the phototrophic organisms which are adapted to the prevailing light conditions are located. 2. Photobioreactor ( 1 ) according to claim 1, characterized in that it comprises ≥ 2 compartments ( 2 ). 3. photobioreactor ( 1 ) according to one of claims 1 to 2, characterized in that the compartments ( 2 ) each have a depth of 5 to 30 mm. 4. photobioreactor ( 1 ) according to one of claims 1 to 3, characterized in that it consists of translucent material. 5. photobioreactor ( 1 ) according to any one of claims 1 to 4, characterized in that it consists of synthetic glass, glass or foils. 6. Photobioreactor ( 1 ) according to one of claims 1 to 5, characterized in that it has devices for introducing gas and devices for supplying a medium and devices for removing the biomass produced in the reactor. 7. photobioreactor ( 1 ) according to one of claims 1 to 6, characterized in that the rear wall ( 2 a) of the rearmost compartment ( 2 ) is made of a stabilizing material. 8. photobioreactor ( 1 ) according to one of claims 1 to 7, characterized in that the compartments ( 2 ) have a plate-shaped geometry. 9. photobioreactor ( 1 ) according to one of claims 1 to 8, characterized in that the compartments ( 2 ) have a tubular geometry. 10. A method for the production of biomass, characterized in that a photobioreactor ( 1 ) according to claims 1 to 9 is used. 11. The method according to claim 10, characterized, that carried out continuous cultivation becomes. 12. The method according to any one of claims 10 to 11, characterized, that carried out continuous cultivation where the biomass concentration is above the Dilution rate is controlled. 13. The method according to any one of claims 10 to 12, characterized in that the cells from the compartment ( 2 ) with the higher, irradiated light intensity are passed into the compartment ( 2 ) with the lower light intensity. 14. The method according to any one of claims 10 to 13, characterized in that different, phototrophic organisms are cultivated in the compartments ( 2 ) which have an absorption spectrum adapted to the wavelength spectrum irradiated into the compartment in each case. 15. The method according to any one of claims 10 to 14, characterized in that cells from a compartment ( 2 ) with a low in a compartment ( 2 ) with a higher light intensity are passed.