RU2451446C1 - Photobioreactor - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to biotechnology and can be used to obtain microalgae biomass and any other life products thereof. The photobioreactor is made from translucent, chemically and biologically inert material in form of a flat panel composed of parallel channels. Below and on top, the outlets of the channels are connected by common containers made from the same material. The common containers have ports for installing sensors which measure pH, temperature and content of dissolved oxygen, and socket pieces for inlet of additives or collecting a suspension of microorganisms. Below each even channel in the light-receiving plane on one side and the odd channel on the other, there are ports for inlet of a gaseous mixture so that the suspension inside the photobioreactor moves due to air lift - upwards in half of the channels and downwards in the other half of the channels.

EFFECT: improved gas-mass exchange characteristics, low amplitude of oscillation of culturing parameters and providing a more compact design, where the photosynthesis process is combined with the gas-mass exchange process.

3 cl, 7 dwg

Description

The invention relates to biotechnology and can be used to obtain biomass of photosynthetic microorganisms, in particular microalgae, create carbon dioxide absorption systems, photosynthetic oxygen production, air regeneration in rooms with difficult ventilation, and also to obtain other valuable vital products of photosynthetic microorganisms.

Microalgae growing apparatuses (photobioreactors) are widely known, consisting of a light-receiving part made in the form of translucent tubes, a fluid movement inducer (pump or airlift), and a gas-mass exchange system (for a review see Gypsies, Laboratory photobioreactors. Appl. Biochem. Microbiol. (2001), 37, 4, p. 387-397; Pulz, O., Photobioreactors: production systems for phototropic microorganisms (2001) Appl Microbiol Biotechnol 57, p. 287-293).

Known planar photobioreactor, consisting of a light receiving part, a motive fluid and a gas exchange system, in which the light receiving part is made in the form of a flat panel of transparent material consisting of parallel channels arranged in 2 rows (O. Pulz. Closed-type planar bioreactor for biomass production microalgae, Fiziol, Rast. (1994), 41 (2), pp. 292-298). These channels are connected in parallel or sequentially with each other, forming a single tubular system through which the suspension of microalgae moves due to the motive agent. In series with the light receiving part, a gas-mass exchange system is installed. The disadvantage of this system is the spatial separation of the processes of photosynthesis and separation of excess oxygen / saturation of the suspension with carbon dioxide. As a result, the culture of photosynthetic microorganisms in such an apparatus is in cyclically changing conditions (oxygen and carbon dioxide content, pH, redox potential, illumination). In addition, during long-term cultivation, the light-receiving surface is surrounded by a film of microalgae. To clean the walls of the light receiving part of the tubular photobioreactors, foam wads are used, which are collected in a dust collector and, if necessary, passed through the tubes of the light receiving part (Lukashin et al. Of the USSR AS No. 1083944, 1984, bull. No. 28, p.15-16). Unfortunately, this method is not applicable for planar photobioreactors in which the channel cross-sectional shape is not a circle.

The closest analogue of the invention is the photobioreactor described in patent CN 101838606 A, publ. 09/22/2010, which consists of a light-receiving part illuminated from one or two sides and made of translucent chemically and biologically inert material, made up of parallel channels, the bottom and top of the channel exits are connected by common containers made of the same material, and they have one or more fittings for introducing additives or taking a suspension of microorganisms and removing gas from the photobioreactor, and ports for introducing the gas mixture are installed at the bottom of the channels so that the suspension inside the photobioreact pa due aerlifta moved both up and down. The disadvantages of this photobioreactor include insufficient uniformity in the supply of carbon dioxide and the selection of excess oxygen.

The aim of the present invention is to eliminate the disadvantages of the prototype and to achieve a technical result consisting in improving gas and gas exchange characteristics, reducing the amplitude of oscillation of the cultivation parameters and providing a more compact structure, where the photosynthesis process is combined with the gas and gas exchange process.

The specified technical result is achieved in a photobioreactor containing a light receiving surface illuminated from one or two sides and made of a translucent chemically and biologically inert material composed of parallel channels, the bottom and top of the channel exits are connected by common containers made of the same material, and they contain one or several fittings for introducing additives or taking a suspension of photosynthetic microorganisms and for removing gas from the photobioreactor, and at the bottom of the channels The ports for introducing the gas mixture have been updated so that the suspension inside the photobioreactor moves up and down, according to the invention, made in the form of a flat panel, in the common capacities of the photobioreactor there are one or more ports for sensors that measure temperature, pH and dissolved content oxygen in a suspension of photosynthetic microorganisms, while ports for introducing a gas mixture are installed at the bottom of each even channel of the light receiving surface on the one hand and the odd channel on the other side which provides airlift movement in half of the channels up, and in half of the channels down.

In particular cases of embodiment, to clean the light-receiving surfaces from the biofilm inside the photobioreactor, a permanent magnet with a cross section approximately equal to the cross-section of the channels is coated with a soft porous chemically and biologically inert material and set in motion by an external magnetic field, while the transition between the light-receiving panel and the containers does not have steps and sudden changes in the angle of inclination of the plane to facilitate the movement of the magnet.

In addition, for simultaneous cleaning of several light receiving surfaces of the channels from the biofilm inside the photobioreactor, magnets are placed in the number equal to or less than the number of channels, simultaneously driven by an external multipole magnet made in the form of a strip, in which the south and north poles alternate with a step equal to the cross section channel.

Figure 1 schematically shows the photobioreactor device, figure 2 is a graph of the change in pH when adding acid, figure 3 is a graph of the change in dissolved oxygen when changing the supplied gas mixture from air to argon, figure 4-5 is a model of a photobioreactor after 3 weeks of cultivation of chlorella, Fig.6-7 - cleaning the layout of the photobioreactor using a magnet.

The photobioreactor (Fig. 1) consists of a light-receiving part (1) made of a translucent chemically and biologically inert material (for example, polycarbonate or plexiglass) in the form of a flat panel composed of parallel channels. The bottom of the channel exits are connected by a common tank (2), and from the top by a common tank (3) made of the same material. In containers (2) and (3) there are one or several ports (4) for sensors that measure temperature, pH, dissolved oxygen in a culture of photosynthetic microorganisms, as well as one or more fittings (5) for introducing the necessary liquid additives or selection samples of a suspension of microorganisms and gas removal from the photobioreactor. A mechanical defoaming device (6) is installed between the upper tank (3) and the gas outlet (5). In addition, at the bottom of each even channel of the light-receiving plane on one side and the odd channel on the other side, ports (7) are installed for introducing the gas mixture. Inside the photobioreactor there is a permanent magnet (8) coated with an inert material to prevent corrosion, as well as a soft porous material used for wiping surfaces (for example, a fabric made of polyvinyl acetate reinforced fiber used for wiping painted surfaces of cars).

Photobioreactor works as follows. Before starting work, sensors are installed in the photobioreactor that measure temperature, pH, dissolved oxygen content, and the necessary communications are connected: gas lines, containers for media, and crop reception. Then it is filled with a sterilizing solution (for example, 10-12% hypochlorite solution) and sterilized. After sterilization, the photobioreactor is washed several times (usually 3-5) with sterile water and filled with sterile nutrient medium specific for the growing photosynthetic microorganism. Then the pH and temperature are adjusted to the required values, a gas mixture is fed into the channels. The photobioreactor is illuminated from one or two sides with any light source (for example, sunlight, LEDs, fluorescent lamps, gas discharge lamps based on mercury or sodium, etc.) suitable for the spectral composition and radiation intensity for the grown microorganism, and a suspension of microorganisms is introduced . The developing culture of microorganisms is saturated with carbon dioxide in the channels where the gas mixture is supplied, and the excess oxygen passes from the liquid to the gas phase. In channels where there is no supply of a gas mixture, a suspension of microorganisms, already saturated with carbon dioxide, moves from top to bottom due to airlift. Thus, the proposed photobioreactor does not additionally require a gas-mass transfer device and a slurry stimulator. In addition, in the channels where the gas mixture is supplied, gas bubbles, rising to the surface, prevent the surface of the film from fouling with a film of photosynthetic microorganisms, thereby facilitating the effective penetration of light into the photobioreactor.

Nevertheless, in the channels where the gas mixture is not supplied, as well as in the channels with the gas mixture, it is possible to form zones with a laminar flow of the suspension, where biofilm wall fouling occurs. To remove the biofilm, a magnet (magnets) (8) is used, driving them along the channel using an external magnet (electromagnet) (not shown in Fig. 1) with a magnetic field sufficient to set the magnet (8) in motion. A magnet (8) coated with soft chemically and biologically inert material passes through the channel and removes the biofilm. The cross section of the magnet should be close to the cross section of the channel in shape, and the cross section of the magnet, taking into account the covering material, should be approximately equal to the cross section of the channel. If only one magnet is used, it is manually transferred from one channel to another using an external magnet and sequentially cleans all the channels from the biofilm. If a system of magnets is used, they are located on the transition surface between the light receiving surface (1) and the capacitance (3). Magnets (8) are held on this surface by an external multi-pole magnet made in the form of a strip with alternating arrangement of the north and south poles with a step equal to the width of the channels. If it is necessary to clean the light receiving surfaces, the external multipolar magnet is manually moved along the channels, dragging magnets behind it (8). After cleaning the surfaces, the external multipolar magnet is returned to its original position, returning the magnets (8), and the external multipolar magnet does not require special fixing, since it is held in the initial position by the force of interaction with the magnets (8). To realize the possibility of cleaning the light-receiving surfaces during the operation of the photobioreactor without disassembling it, the transition surface between the light-receiving surface (1) and the containers (2) and (3) should not have steps and sharp changes in the angle of inclination.

Example 1

To verify the mass transfer characteristics of the photobioreactor, a mock-up was made on the basis of 16 mm thick commercially available cellular polycarbonate with a rectangular section of cells located in 2 rows. A segment of 35 pairs of honeycombs with a height of 90 cm was used, attaching to the panel the lower (2, Fig. 1) and upper (3, Fig. 1) containers of 0.9 l each. At the bottom of the honeycomb polycarbonate panel there are ports for gas entry (in even cells - channels on the one hand, and in odd ones on the other). The photobioreactor model thus created with a useful volume of 10.24 l was filled with a nutrient medium for growing microalgae containing (g / l): NH ₄ Cl - 0.5; MgSO ₄ 7H ₂ O - 0.02; CaCl ₂ 2H ₂ O - 0.01; KH ₂ PO ₄ - 0.77; K ₂ NRA ₄ - 1.44; NaHCO ₃ - 0.5; EDTA - 0.05; ZnSO ₄ 7H ₂ O - 0.022; H ₃ BO ₃ 0.0114; MnCl ₂ 4H ₂ O - 0.00506; FeSO ₄ 7H ₂ O - 0.00499; CaCl ₂ 6H ₂ O - 0.00161; CuSO ₄ 5H ₂ O - 0.00157; (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O - 0.0011. The pH of the obtained medium without titration was 10.7. When supplying air as a gas phase, it was found that a steady outflow of air from all channels began at a flow rate of 0.7 l / min. With an increase in the feed rate of the gas phase above 2 l / min, it was found that in some channels the gas phase occupied almost the entire channel in height, i.e. there was an ineffective mixing of gas and liquid. Thus, the working flow rate of the gas phase lies in the range of about 0.7-2.0 l / min. If carbon dioxide is added to the gas phase for a short time (10 sec) to 10% by volume, then the pH is shifted to a value of 5.5 within about 30 sec after addition (data not shown). To test the effectiveness of horizontal mixing in the reactor, a pH sensor was introduced into the center of the reactor from below, and an acid addition (1 ml of 1 N solution) was made to the lower part of the extreme channel. The course of the pH change is shown in figure 2, it can be seen that more than 95% of the response to such an asymmetric additive was achieved in less than 1700 seconds. Moreover, the pH changes were monotonic, without oscillation, which favorably distinguishes the described model from the loop photobioreactor, in which such an additive led to pH oscillations for more than 2000 sec (Tsygankov, Laboratory photobioreactors. Prikl. Biochemical. Microbiol. (2001), 37 4, p. 387-397).

To measure the gas-mass transfer characteristics (K _L a), the gas phase at a feed rate of 1 l / min was changed from air to argon and the kinetics of changes in the dissolved oxygen content was measured (Fig. 3, a curve in the form of dots). The approximation of the obtained curve (curve in the form of a line in figure 3) was carried out in accordance with the equation

dO _i / dt = K _L a (C * -O _L ),

where O _L is the concentration of dissolved oxygen, expressed in micromoles, at the moment;

C * is the concentration of dissolved oxygen at the initial moment (232 μM);

K _L a - mass transfer coefficient from a liquid to a gas phase.

The value of K _L a obtained by approximation was 0.0036 ± 0.00005 sec ^-1 . This value is approximately twice as high as that described for the tubular photobioreactor 0.0015 (Tsygankov AA, Borodin VB, Rao KK, et al. H ₂ photoproduction by batch culture of Anabaena variabilis ATCC 29413 and its mutant PK84 in a photobioreactor. Biotechnology And Bioengineering 1999 64 (6): 709-715), which confirms the advantages of the proposed photobioreactor.

Example 2

To demonstrate the ability to clean the photobioreactor using a magnet located inside, the photobioreactor described in Example 1 was used to cultivate chlorella. Cultivation was carried out in the medium described above. The pH of the medium (7.3) was maintained using an external pH regulator by installing a Mettler Toledo InPro 3030 pH sensor in the photobioreactor and supplying carbon dioxide to the medium with an increase in pH above a specified value. Illumination (50 W / m ² ) during cultivation was carried out using an LED panel based on a RoHS Dreamled 3528 light strip. The temperature was controlled by automatically turning on the fans (30 ° C). After 3 weeks of cultivation (diluting the culture every 3 days with fresh medium), the culture was drained and the photobioreactor was filled with distilled water. The channels of the photobioreactor into which the gas phase was not supplied were covered with a film of microalgae (Figs. 4-5). A magnet in the form of a disk with a thickness of 2 mm and a diameter of 20 mm, coated with artificial material used to wipe painted surfaces of cars, was installed in the photobioreactor. Using an external magnet, an internal magnet was introduced into the channels and carried along them (Fig. 5). As a result, after the passage of the magnet, the channel surface was cleaned, and a suspension of microalgae formed in the channel (Fig. 6). This indicates the achievement of the beneficial effect of using a permanent magnet.

Claims (3)

1. A photobioreactor, consisting of a light receiving surface illuminated from one or two sides and made of translucent chemically and biologically inert material, composed of parallel channels, the bottom and top of the channel exits are connected by common containers made of the same material, and in them one or more fittings are located for introducing additives or taking a suspension of photosynthetic microorganisms and for removing gas from the photobioreactor, and ports for introducing the gas mixture are installed at the bottom of the channels the suspension inside the photobioreactor moved due to airlift both up and down, characterized in that it is made in the form of a flat panel, the containers also have one or more ports for sensors that measure temperature, pH and the content of dissolved oxygen in the suspension of photosynthetic microorganisms, ports for entering the gas mixture are installed at the bottom of each even channel of the light receiving surface on one side and the odd channel on the other side, which ensures airlift movement in the channel half up, and in half of the channels - down. 2. The photobioreactor according to claim 1, characterized in that for cleaning the light-receiving surfaces of the biofilm, a permanent magnet is arranged inside it with a cross section approximately equal to the cross-section of the channels, coated with a soft, porous chemically and biologically inert material and set in motion by an external magnetic field, with the transition between the light-receiving panel and capacitors do not have steps and sharp changes in the angle of inclination of the plane to facilitate the movement of the magnet. 3. The photobioreactor according to claim 2, characterized in that for simultaneous cleaning of several light-receiving surfaces of the channels from the biofilm, magnets are arranged inside it in a number equal to or less than the number of channels, and simultaneously driven by an external multipolar magnet made in the form of a strip, in which the south and north poles alternate in increments equal to the cross section of the channel.

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