Photobioreactor with improved light input through increase in surface area,
a wavelength shifter or light transport
DESCRIPTION
The invention relates to a novel photobioreactor for producing biomass.
Photobioreactors are fermenters in which phototrophic microorganisms, such as algae,
cyanobacteria and purple bacteria are cultivated, that is to say in which either the growth and
the propagation of these cells is made possible or the production of various substances is
promoted by means of phototrophic cells.
Such photobioreactors are described, for example, in the following publications:
(i) "Biomass and Icosapentaenoic Acid Productivities from an Outdoor Batch Culture of
Phaeodactylum tricornutum UTEX 640 in an Airlift Tubular Photobioreactor", Appl.
Microbiol. Biotechnol. (1995), 42, pp. 658-663,
(ii) "Autotrophic Growth and Carotenoid Production of Haematococcus pluvialis in a 30
Liter Air-Lift Photobioreactor", Journal of Fermentation and Bioengineering (1996), Vol.
82, No. 2, pp. 113-118,
(iii) "Light Energy Supply in Plate-Type and Light Diffusing Optical Fiber Bioreactors",
Journal of Applied Phycology (1995), 7, pp. 145-149,
(iv) "A Simplified Monodimensional Approach for Modeling Coupling between Radiant
Light Transfer and Growth Kinetics in Photobioreactors". Chemical Engineering Science
(1995), Vol. 50, No. 9, pp. 14S9-1500.
In addition, the publication DE 44 40 081 Al describes a method and a device for increasing
the productivity in biocollectors for phototrophic microorganisms in which the surface for
colonization by biocatalysts is increased by introducing a porous layer. At the same time, the
flow over the colonized surfaces is ensured in that the upward-flowing culture substrate is
passed through the porous layer. Aligning the porous channels in the sunlight can guarantee
an optimum utilization of light falling on the reactor at an angle. The method is suitable for
the production of excretion products of phototrophic microorganisms and microalgae.
US Patent 4 952 511 describes a photobioreactor for cultivating photo synthetic
microorganisms. Said photobioreactor comprises a tank, at least one light chamber that
extends into the tank and at least one high-intensity lamp whose light is conducted into the
light chambers. Each of the light chambers has at least one transparent wall and a device for
the essentially uniform distribution of the light of the lamp over the transparent wall.
Finally. US Patent 3 959 923 describes a device for cultivating algae in which water flows,
together with the algae and nutrients, alternately through wide, dark zones and narrow,
illuminated zones along meandering flow channels.
A principle field of application of photobioreactors is the production of microalgae, which
have a share of 30% of the primary production of biomass generated worldwide. In this
connection, they are the most important CO2 consumers. Microalgae are therefore capable of
having an environmental load reduction effect if they are used for regenerative material
production. Materials that are produced in this way then contribute to the reduction of C02
emission into the atmosphere since they replace fossil-produced materials.
The microalgae include, on the one hand, the procaryotic cyanobacteria as well as eucaryotic
microscopic algae classes. These organisms supply a wide variety of substance classes that
can be used for pharmaceutical, cosmetic, nutritional and animal nutrition purposes and for
technical purposes (for example, heavy-metal adsorption). Important substance classes in
this connection are lipophilic compounds, such as, for example, fatty acids, lipids, sterols
and carotenoids, hydrophilic substances such as polysaccharides, proteins or amino acids
and phycobilin proteins (pigments), and also the total biomass as protein-rich raw material
low in nucleic acid.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 shows the cross-section of various photobioreactors having
increased surface areas wherein:
Figure 1a shows a meander-shaped reactor surface;
Figure 1b shows a sinusoidal reactor surface and
Figure 1c shows a reactor having light transparent
Figure 2 shows a photobioreactor according to the present invention
which employs the basic principle of an airlift loop reactor.
Figure 3 shows a plate-fin column photobioreactor according to the
present invention.
Figure 4 shows a tube reactor having recesses according to the
invention.
Figure 5 are graphs showing growth rate and productivity of Chlorella
vulagaris as a function of cell concentration in reactors with and
without lateral recesses.
In the Federal Republic of Germany, as also on an international scale, there is an increasing
trend to replace synthetic active ingredients by using natural substances having equivalent or
improved application properties. Of increasing interest are antioxidant active ingredient
complexes and polyunsaturated fatty acids having therapeutic potency in the field of
cosmetics, medicine and the health food market. These attractive antioxidants include the
tocopherols (vitamin E) and carotenoids, such as p-carotene and astaxanthin.
The cost effectiveness of the substances produced by microalgae is primarily determined by
the productivity of the selected algae species. But only if, at the same time, a high efficiency
of conversion of solar radiation energy into the desired biomass form is achieved and the
energy consumption and the costs of production, installation and plant operation are kept
extremely low. High biomass productivity is a problem of optimum light distribution per
unit volume. The absorption of light by algae results in a severe decrease in light with
increasing layer thickness and, at the same time, a mutual self-shadowing takes place. This
phenomenon results in a theoretical layer formation in the reactor:
(1) an outer algae layer that is exposed to high light intensities that may result in photo
inhibition,
(2) a central layer having ideal illumination,
(3) an inner algae layer having a light deficiency and a high respiration rate.
The object of the invention is therefore to provide a photobioreactor in which the solar
radiation available is coupled in and can be distributed in such a way that all the
microorganisms have an equally high photosynthesis activity regardless of position.
The invention relates to a photobioreactor that has a reactor chamber having an increase in
surface area that is greater than the planar enveloping surface of a volume.
Said increase in surface area results in a better spatial distribution of the light over the
reactor cross section and consequently in an optimization of the light intensity in the entire
reactor compared with the photobioreactors known in the prior art. The reactor chamber of
the latter normally comprises pipes or so-called "tubes". Their cross section is circular. In
addition, photobioreactors are known that have reactor chambers whose cross section is
rectangular. Such a cross section has more area as a volume envelope than the circular cross
section of a pipe. This is shown diagrammatically in Figure 1.
The photobioreactor according to the invention has an increase in surface area compared
with the abovementioned known reactor geometries, as is shown by way of example in
Figure 1. Here, (a) denotes a meander-shaped and (b) a sinusoidal reactor surface, (c)
denotes a reactor geometry having light-transparent webs. A further embodiment is shown in
Figure 4 in which glass extensions inwards represent the increase in surface area.
Common to all these geometries is the fact that the reactor surface area is increased
compared with known geometries.
In the photobioreactor according to the invention, all the reactor chamber geometries can in
principle be used that have an increase in surface area compared with the planar envelope
(square or rectangular in cross section).
The reactor chamber of the photobioreactor according to the invention is composed of a
light-transparent material, preferably glass or plexiglass.
In accordance with a further embodiment of the invention, the surface-area-increasing
geometry of the reactor chamber is achieved by a glass tube into whose interior glass
extensions project. Said glass extensions are mounted perpendicularly or at an angle on the
internal surface in an alternating manner.
At the same time, the glass extensions increase the turbulence in the liquid phase. Instead of
glass, it is also possible to use another light-transparent material, such as, for example,
plexiglass.
Increasing the turbulence achieves the so-called "flashing-light effect". The flashing-light
effect means that a high light intensity at short intervals (> 1 Hz) is sufficient for a
maximum photosynthesis activity. This can be achieved by a turbulent flow conduction in
the reactor that exposes the cells at short intervals to high light intensities at the reactor
surface and they can therefore process the light energy collected in the subsequent dark
phases.
The invention therefore relates, furthermore, to a photobioreactor whose reactor chamber
has, in addition to an increased surface area, devices for producing a turbulent flow
conduction.
As already mentioned, said turbulence can be achieved by a surface-area-increasing
geometry of the reactor chamber, in particular by glass extensions that are situated on the
interior wall of the reactor chamber. A turbulent flow conduction may also be achieved,
furthermore, by installing static mixers (baffles). Like the abovementioned glass extensions,
these internals can, in addition, conduct light additionally into the reactor. A further way of
generating turbulence in the photobioreactor according to the invention is to provide an
gassing device that achieves the desired effect at an appropriate gassing rate. The provision
of flow-conducting internals can also improve the flashing-light effect if a defined frequency
is established for the illumination time.
The intense mixing with as much turbulence as possible results in a light distribution by
bringing the algae to the light. This can control the frequency and the duration of the
"illumination phases" in a defined manner.
The energy density in the reactor chamber of the photobioreactor according to the invention
may, furthermore, be increased by using so-called wavelength shifters. The wavelength
shifter converts the component of the light not absorbed by phototrophic microorganisms in
such a way that as large a component of the light as possible or the totality of the radiation is
displaced into that frequency band that can be absorbed by the photocentre of phototrophic
microorganism used. Consequently, the holometric radiation density is specifically increased
in such a way that the productivity is substantially increased per unit reactor volume
compared with bioreactors irradiated with normal light.
In this case, the wavelength shifter may be disposed between a reflector and the actual
reactor chamber. The wavelength shifter may, however, also be provided between the light
source and the reactor chamber, with the result that the reflector can be omitted.
Omission of the reflector is likewise possible if the wavelength shifter is in the form of rods,
plates, fibres or particles in the reactor chamber. Furthermore, the wavelength shifter can
also be a coating directly on the reactor wall on the outside or inside of the reactor chamber.
Substances that are capable of displacing the wavelength are known per se to the person
skilled in the art and are described, for example, in the following publications:
E. Locci et al., "Test of a Lead-Plexipop Calorimeter Module Viewed by Wave Length ,
Shifter Bars", Nucl. Instrum. Methods 164, (1979), pp. 97-104,
S.W. Han et al., "Radiation Hardness Tests of Scintillating Tile/WLS Fiber Calorimeter
Modules", Nucl. Instrum. Methods A365 (1995), pp. 327-351.
The wavelength shifters used in the photobioreactor according to the invention preferably
comprise fluorescent substances. Such fluorescent substances are substances that, after
absorption of light, radiate light again, the energy for the radiated light not being essentially
drawn from the heat content of the fluorescent substance, but originating from the excitation
energy supplied by the absorbed light.
The fluorescent substance may be contained in a carrier, such as an organic or inorganic
glass.
For example, organic fluorescent substances may be contained in organic glasses, such as
acrylic glass polycarbonate or acrylic glass polystyrene. Ions of rare earths, which can
likewise be used as fluorescent substances, are preferably contained in inorganic glasses.
Solutions of the fluorescent substances in transparent solvents can also be used as
wavelength shifters.
The fluorescent substances have the property of absorbing light and reemitting it, in general
after a very short time (frequently only a few nsec). It is important that this reemission of the
light occurs virtually without loss in some substances, i.e. the fluorescent quantum yield
(number of emitted photons divided by the number of absorbed photons) is > 90%, often
close to 100%. It is furthermore of importance that the fluorescent spectrum is displaced
towards longer wavelengths compared with the absorption spectrum, i.e. a dyestuff converts
UV and violet light into blue light, or another blue light into green light, etc. As a result of
combining a plurality of dyestuffs, either in the same plate or, for example, by layers behind
one another of differently coloured plates, a larger wavelength range can also be leapt over
in one step, for instance blue light can be converted directly into red light.
Expected of a wavelength shifter is high fluorescent quantum yield, good solubility in the
carrier material provided (in order to be able to achieve sufficiently high light absorption),
an optimum position of absorption spectrum and emission spectrum for the particular
application and a sufficiently long-term stability under the conditions of use envisaged.
Typical examples of the use of wavelength shifters are whiteners in detergents, UV-
absorbing dyestuffs that emit blue to mask the yellowing of washing, and the dyestuffs that
are used in scintillation counters to shift shortwave Cerenkov radiation or scintillation
radiation to a wavelength range that is optimum for the spectrosensitivity of the
photodetectors used.
Preferred examples of organic fluorescent substances that can be used as wavelength shifters
in the photobioreactor according to the invention are the following naphthalimides and
perylene derivatives:
N,N'-bis(2,6-diisopropylphenyl)perylene-3,4:9,10-tetracarboxylic diimide or N,N'-bis(2,6-
diisopropylphenyi)-l,6,7,12-tetraphenoxyperylene-3.4: 9.10-tetracarboxylic diimide.
These fluorescent substances all have a very high quantum yield. The maximum
absorbances are many 10,000 1/mol-cm.
The fluorescent substances may be present in the carrier material in a concentration of 10"7
to 10"2 mo 1/1. The carrier material preferably then has a thickness of 0.1 to 10 mm.
The use of a wavelength shifter in combination with the better spatial distribution of light
over the reactor cross section by establishing an appropriate surface area/volume ratio and
the increase in turbulence to achieve a flashing-light effect distribute the light optimally in
the reactor chamber of the photobioreactor according to the invention.
Figure 2 shows the structure of the photobioreactor according to the invention employing the
basic principle of an airlift loop reactor. The reactor has a rectangular cross section and two
internal surfaces (1) that extend parallel to the reactor chamber walls, devices for injecting
air (2) at the lower side of the reactor chamber and devices for supplying (3) a medium and
for removing (4) the biomass produced in the reactor chamber.
The internal surfaces serve at the same time as a guide tube.
Plexiglass, for example, which has a high light transparency, can be used as material.
The thorough mixing takes place as a result of injection of air at the lower side of the
reactor, with the result that the liquid flows upwards and back down again at the side. The
gas exchange and the temperature control take place in the highly turbulent headspace. The
temperature control in the headspace eliminates an additional plexiglass wall that would be
necessary in the case of a cooling jacket.
The rectangular basic structure and the small reactor depth result in a large surface
area/volume ratio and, consequently, the possibility of a high light input into the reactor. The
reactor does not have unilluminated zones, with the result that sufficient light can
continuously be provided for the cells.
Operation as an airlift loop ensures a high turbulence with low shearing forces acting on the
algae cells. Given high turbulence and, at the same time, high radiation intensity, the
flashing-light effect can be utilized, according to which the cells do not have to be
continuously illuminated. The turbulence can be increased either by the gassing rate or by
the installation of static mixers (baffles).
A flow conduction with high turbulence results in a horizontal mixing in addition to vertical
mixing. This subjects the phototrophic microorganisms to an interrupted light provision. The
cycle time that a phototrophic microorganism spends in the light and then in the dark should
be > 1 Hz. The turbulence determines the time the microorganisms need in order to be
transported back into the illuminated zone again from the unilluminated zone. The length of
the transport path is determined by the layer thickness of the reactor (reactor depth).
The installation of flow-conducting elements increases the turbulence and, consequently, the
frequency of the transport of the microorganisms from the unilluminated zone into the
illuminated zone again can be improved.
In addition, like the recesses in the Vigreux column, said flow-conducting elements could
additionally conduct light into the reactor.
The thorough mixing and constant gas flow in the reactor ensure a good introduction of CO2
and discharge of O2.
The simple geometry and the arrangement of the degassing zone in this system make simple
scaling-up possible.
Instead of a reactor employing the airlift loop principle, the reactor may also be designed as
a plate-fin column.
Such a plate-fin column is shown diagrammatically in Figure 3. In the latter, (5) denotes a
reactor chamber having a rectangular cross section that has internal walls (6, 7) extending
parallel (6) and at a right angle (7) to the reactor walls (5).
The plate-fm column has, furthermore, devices for injecting air at the lower side (8) of the
reactor chamber, and devices for supplying a medium (9) and for removing the biomass (10)
produced in the reactor chamber.
The internal surfaces (6, 7) serve to generate a turbulent flow. Mixing takes place as a result
of injection of air at the lower side of the reactor, with the result that the liquid first flows
upwards and then back down again at the side. The transverse walls (7) deflect the gas
bubbles and result in a flow and vortex formation in the next cell. Gas exchange takes place
in the headspace. As a result of the vortex formation in the individual cells, an intensive
mixing takes place over the reactor cross section.
The airlift loop reactors described above can also be disposed alongside one another in
series, in which case they are connected to one another on the fluid side by the principle of
communicating tubes.
The bioreactor according to the invention may also be designed in such a way that it has a
plurality of airlift loop reactors that are disposed above one another as plate-fin column.
Finally, Figure 4 shows diagrammatically the structure of a reactor chamber that is designed
as a glass tube into whose interior glass extensions project.
The invention is explained in greater detail by the exemplary embodiment below.
Exemplary7 embodiment
A tube reactor was extended by the recesses shown in Figure 4. Said recesses have a double
function in that they both increase the reactor surface area and influence the flow. Vigreux
columns are constructed on this principle (likewise for reasons of increase in surface area)
and were used directly for comparison tests. A tube reactor having the same geometry
without lateral recesses was used as a control. The illumination took place by means of 2
halogen radiators, with the result that 520 uE/(m2*s) of light was available from one side.
The radiated light intensity per unit volume and time was, however, 10% lower in the
control reactor than in the Vigreux column.

Direct comparison revealed a 20 to 40% higher productivity in the Vigreux column with 4 g
of DW/1 and 30 to 100%) higher productivity with 5 g of DW/1 (cf. Figure 5) in the Vigreux
column compared with the reactor without lateral recesses. (The different results in VI and
V2 are the result of a different preliminary adaptation of the algae cells to the light.)
This shows that an increase in surface area that simultaneously also increases the turbulence
can markedly increase the biomass productivity in the case of intensities above the
saturation range.
WE CLAIM:
1 m A photobioreactor comprising a reactor chamber having sidewalls made of
light-transparent material defining an interior volume, _
characterized in that said reactor chamber has a geometry, such as herein described, that enables an
increase in surface area greater than the planar enveloping surface of the interior volume of the
reactor chamber.
2. A photobioreactor as claimed in Claim 1, wherein the reactor chamber
further comprises devices for producing a turbulent flow conduction.
3. A photobioreactor as claimed in Claim 1, further comprising elements that
conduct light into the reactor chamber from the outside.
4. A photobioreactor as claimed in Claim 1, wherein one or more sidewalls of
the reactor have a meander-shaped or sinusoidal cross-section.
5. A photobioreactor as claimed in Claim 1,
wherein the reactor chamber further
comprises light-transparent webs projecting into the interior of the reactor chamber.
6. Aphotobioreactor as claimed in Claim 1, wherein the reactor chamber
comprises a glass tube comprising glass extensions projecting into the interior of the reactor
chamber.
7. A photobioreactor as claimed in Claim 1, wherein the reactor chamber is an
airlift loop reactor or a plate-fin column.
8. A photobioreactor as claimed in Claim 7, wherein the reactor chamber has
a rectangular cross-section, internal surfaces extending parallel to the reactor chamber sidewalls,
air injectors at a lower side of the reactor chamber, and a medium supply tank and a biomass
reservoir in fluid communication with the interior of the reactor.
9, A photobioreactor as claimed in Claim 7, comprising a plurality of airlift
loop reactors connected in series, wherein the interior of each reactor is in fluid communication
with an adjacent reactor.
! o A photobioreactor as claimed in Claim 7, comprising a plurality of airlift
loop reactors arranged vertically to form a plate-fin column.
.11. A photobioreactor as claimed in Claim 1, further comprising a wavelength
shifting compound.
12. A photobioreactor comprising at least one reactor chamber having sidewalls
made of light-transparent material, wherein the reactor chamber comprises a first internal surface
having first and second opposed edges, wherein the first and second opposed edges of the first
internal surface are each spaced from an interior surface of the reactor chamber.
13. The photobioreactor as claimedin Claim 12, fancier comprising:
at least one injector;
a medium supply tank; and
a biomass reservoir;
wherein the at least one injector, the medium supply tank and the biomass reservoir are in
fluid communication with the interior of the reactor chamber.
j4 The photobioreactor as claimed in Qaim 12, wherein the photobioreactor comprises a
plurality of reactor chambers, and wherein the interior of each reactor chamber is in fluid
communication with the interior of at least one other reactor chamber.
15. The photobioreactor as claimed in Claim 14, wherein the reactor chambers are arranged
vertically to form a column having a bottom reactor chamber, wherein an upper surface of the
bottom reactor chamber forms a lower surface of an adjacent reactor chamber.
16. The photobioreactor as claimed in Qaim 14, wherein the reactor chambers are connected
together with pipes or tubes.
17. The photobioreactor as claimed in Claim 12, wherein the photobioreactor further
comprises a wavelength shifting compound incorporated into a surface of the reactor or coated
onto a reactor sidewall.
18. The photobioreactor as darned mQaml7, where^
is selected from the group consisting of 4,5-dimethoxy-N-(2-ethyl-hexyl)naphthalamide; 3,9-
Di(i-butoxycarbonyl)-4,10-dicyanoperylene;N,N'-bis(2,6-dusopropylphenyl)perylene-3,4:9,10-
tetracarboxylic diimide; and N,N'-bis(2,6-diisopropylphenyl)-l,6J7,12-tetraphenoxyperylene-
3,4:9,10-tetracarboxylic diimide.
19. The photobioreactor as claimed in Claim 12, wherein the reactor chamber further
comprises a second internal surface spaced from the first internal surface, the second internal
surface having first and second opposed edges, wherein the first and second opposed edges of the
second internal surface are each spaced from an interior surface of the reactor chamber.
20. The photobioreactor as claimed in Claim 12, wherein the reactor chamber has a
rectangular cross-section.
21. A method of cultivating phototropic microorganisms in a reactor as claimed in
Claim 12, the method comprising:
supplying the reactor with medium comprising phototropic microorganisms;
injecting a gas into the reactor such that medium in the reactor flows upwardly in a first
internal region, impinges on an interior surface of the reactor and flows over the first opposed
edge of the first internal surface, wherein at least a portion of the medium flowing over the first
opposed edge flows downwardly in a second internal region, impinges on an interior surface of
the reactor, and flows over the second opposed edge of the first internal surface to be recirculated
into the first internal region;
impinging light from a light source onto the reactor; and
removing biomass produced in the reactor chamber.
22. The method as claimed in Claim 21, wherein the light impinges on a wavelength shifting
substance.
. 23. The method as claimed in Claim 22, wherein the wavelength shifting substance
comprises a fluorescent compound selected from the group consisting of 4,5-dimethoxy-N-(2-
ethyl-hexyl)naphthalamide; 3,9-Di(i-butoxycarbonyl)-4,10-dicyanoperylene;N,N'-bis(2,6-
diisopropylphenyl)perylene-3,4:9,10-tetracarboxylic diimide; and N,N'-bis(2,6-
diisopropylpheny^-l.SJ.n-tetraphenoxyperylene-S^^.lO-tetracarboxylicdiimide.
24. The method as claimed in Claim 21, wherein the medium flows turbulently through the
reactor.
25. A method of cultivating phototropic microorganisms in a reactor as claimed in
Claim 19, the method comprising:
supplying the reactor with medium comprising phototropic microorganisms;
injecting a gas into the reactor such that medium in the reactor flows upwardly in a first
internal region between the first and second internal surfaces, impinges on an interior surface of
the reactor and flows over the first and second internal surfaces, wherein medium flowing over
the first opposed edge of the first and second internal surfaces flows downwardly in second and
third internal regions, respectively, impinges on an interior surface of the reactor and flows over
the second opposed edge of the first and second inner surfaces, respectively, to be recirculated
into the first internal region;
impinging light from a light source onto the reactor; and
removing biomass produced in the reactor chamber.
26. The method as claimed in Claim 25, wherein the light impinges on a wavelength shifting
substance.
27 The method as claimed in Claim 26, wherein the wavelength shifting substance
comprises a fluorescent compound selected from the group consisting of 4,5-dimethoxy-N-(2-
emyl-hexyl)naphmalamide;3,9-Di(i-butoxycarbonyl)-4,10-dicyanoperylene;N,N,-bis(2,6-
diisopropylphenyl)perylene-3,4:9,10-tetracarboxylic diimide; and N,N'-bis(2,6-
diisopropylphenyl)-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxylic diimide.
2 8. The method as claimed in Claim 25, wherein the medium flows turbulently through the
reactor.
29. A photobioreactor comprising a tubular reactor chamber made of light-
transparent material, the reactor chamber comprising a plurality of projections extending from the
reactor wall into the interior of the reactor chamber.
30. The method as claimed in Claim 29, wherein the projections are elongate projections
having a major dimension oriented perpendicularly to the reactor surface.
31. The method as claimed in Claim 29, wherein the projections are elongate projections
having a major dimension oriented at an angle to the reactor surface.
32. The method as claimed in Claim 29, wherein the projections are made of light-transparent
material.
33. A method of cultivating phototropic microorganisms in a reactor as claimed in
Claim 29, the method comprising:
flowing medium comprising phototropic microorganisms through the reactor chamber;
and
impinging light from a light source onto the reactor.
34. The method as claimed in Qaim 33, wherein the light impinges on a wavelength shifting
substance.
35. The method as claimed m Claim 34, wbarm me wavelength shifting substo
comprises a fluorescent compound selected from the group consisting of 4,5-dimethoxy-N-(2-
emyl-hexyl)naphmalarmde;3,9-Di(i-butoxycarbonyl)-4,10-dicyanoperylene;N,N,-bis(2,6-
diisopropylphenyl)perylene-3,4:9,10-tetracarboxylic diimide; and N,N'-bis(2,6-
diisopropylphenyl)-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxylic diimide.
36. *tonKfoodMciaimedmaBta33fT^^
reactor.

A photobioreactor is described that has a reactor chamber that is made of light-transparent
material and that has an increased surface area.