CN101899385B - Improve the closed photo bioreactor of the efficiency of light energy utilization that microalgae mass is cultivated - Google Patents

Abstract

The invention belongs to the field of biotechnology, and relates to a closed photobioreactor for improving the light energy utilization rate of microalgae scale cultivation. There are at least two baffles perpendicular to the flow direction of the culture solution on the inner wall of the illuminated surface of the closed photobioreactor, and the area between the baffles covers the effective distance between the inlet and outlet of the culture solution of the photobioreactor. Part or all of the area of the illuminated surface; the length of the baffle in the plate photobioreactor is 30% to 100% of the width of the culture solution flow channel in the plate photobioreactor; the circular tube photobioreactor or oval tube The length of the baffle in the photobioreactor is 30% to 100% of the section arc length of the illuminated surface of the culture fluid channel. The closed photobioreactor of the invention can effectively improve the utilization rate of light energy in the scale cultivation of microalgae cells, and increase the yield of microalgae cells. The closed photobioreactor with the structure of the invention is suitable for large-scale cultivation of various microalgae and production of related products.

Description

A Closed Photobioreactor for Improving the Light Energy Utilization Efficiency of Microalgae Scale Cultivation

technical field

The invention belongs to the field of biotechnology, and relates to a closed photobioreactor with a special internal structure. The closed photobioreactor can effectively improve the light energy utilization rate of microalgae cell scale cultivation and increase the output of microalgae cells . The closed photobioreactor with this structure is suitable for large-scale cultivation of various microalgae and production of related products.

Background technique

Human beings have used microalgae for hundreds of years, and the research and development of microalgae has become more and more in-depth. Microalgae has become an important source of materials in the fields of human food, medicine, dyes, and fine chemicals. At present, with the depletion of fossil energy such as petroleum and coal, people have paid great attention to biorefinery based on biomass. As an important renewable energy source, microalgae can provide a large amount of biomass (oil, starch, cellulose) , has broad application prospects in the field of biorefinery.

The large-scale cultivation of microalgae mainly includes open cultivation and closed cultivation. Open culture is the earliest developed and most widely used method. At present, countries around the world, especially China, still use it as the main method for industrialized cultivation of microalgae (BorowitzkaL.T., BioresourceTechnology, 1991, 38: 251-252; Terry K. Land Raymond., Enzyme and Microbial Technology, 1985, 7: 474-487). Representative reactors include raceway culture tanks and circular culture tanks. The main disadvantages of this culture method are low utilization rate of light energy, great influence by external environmental factors, easy pollution, and large water evaporation.

Compared with open culture, closed culture is less likely to be polluted, saves water resources, has high culture density, and low harvest cost. The disadvantage is high investment cost (LeeY-K., Journal of Applied Phycology, 2001, 13: 307-315; TsygankovA. A., Applied Biochemistry and Microbiology, 2001, 37(4): 333-341; Pulz O., Applied Microbiology and Biotechnology, 2001, 57: 287-293). In order to overcome the defect of high cost of closed culture, on the one hand, it is necessary to reduce the cost of materials and energy consumption required for culture, and on the other hand, it is necessary to greatly increase the yield. Although the yield of closed culture is higher than that of open culture, the light energy utilization efficiency of microalgae is still very low. Trying to improve the utilization rate of light energy by algae cells is an important way to increase yield and reduce cost.

The photosynthetic process of microalgae can be divided into two stages, called light reaction and dark reaction. In the photoreaction stage, algal cells receive photons and convert them into chemical energy; in the dark reaction stage, algal cells use chemical energy to synthesize cell components. In the dark reaction stage, algae cells do not need light or even light is harmful. Therefore, for a single algal cell, continuous illumination means a waste of photons.

On the other hand, in a photobioreactor for large-scale cultivation and at normal cell densities, the light will rapidly attenuate when propagating in the culture medium, and the light penetration distance is several millimeters, which is only about 1mm at high cell densities. In fact, the photobioreactor can be divided into two parts: the light area near the inner wall of the illuminated surface and the dark area outside. If the algae cells are frequently replaced in the light area and the dark area of the photobioreactor at a specific frequency (usually higher than 1 Hz), a "flash effect" will be produced, and the utilization rate of light energy will be greatly improved (JanssenM, SlendersP , TramperJ, et al., Enzyme Microbial Technology, 2001, 29: 298-305; MatthijsH.C.P, BalkeH, MurL.R, et al., Biotechnology and Bioengineering, 1996, 50: 98-107). That is, when the algal cells shuttle back and forth between the light area and the dark area of the photobioreactor, the algal cells that have received the light can enter the dark area in time to perform the dark reaction, and at the same time make the algal cells that have completed the dark reaction return to the light area. The area receives light again, so that the light quanta entering the photobioreactor are fully utilized. Therefore, by strengthening the mixing of the culture solution, the algae cells shuttle back and forth between the light area and the dark area at a high frequency, which can improve the overall light energy utilization rate and the yield of algae cells.

However, in the traditional closed photobioreactor, the flow mixing of the culture medium is not ideal yet. Taking tube-type and plate-type photobioreactors as examples, the diameter of tube-type photobioreactors (straight tubes, bent tubes and spiral tubes, etc., which can be placed horizontally, inclined or vertically) is between 1 and 10 cm The thickness of plate photobioreactors (horizontal, inclined, vertical, etc.) varies from 1 to 10 cm, and the inner walls of these photobioreactors are often smooth. Limited by the wall of the reactor, the mixing of the culture solution near the inner wall is insufficient, and the speed of the algae cells perpendicular to the flow direction (hereinafter referred to as the light path direction) is very small, making it difficult to shuttle between the light area and the dark area. Algal cells located near the inner wall of the illuminated surface for a long time will produce photoinhibition or even photodamage (that is, excessive light); while algal cells that are far away from the inner wall of the illuminated surface are in a state of light limitation (that is, insufficient light) for a long time, making the light The utilization rate is not high.

The mixing of the culture solution can be strengthened through the design of a certain internal structure. CN200720148293.3 and CN200610026539.X respectively add hollow baffles in column type and board box photobioreactors to strengthen the flow and mixing of culture solution. At the same time, internal light sources can be installed in the hollow baffles or used as Gas distribution device. Although this kind of device equipped with hollow baffles can play the role of mixing culture solution, it has a complicated structure and high manufacturing cost, and the mixing of algae cells is disorderly mixing, so it is difficult to ensure that the algae cells are exposed to light in a specific period.

Contents of the invention

The purpose of the present invention is on the basis of the existing tubular or plate-type closed photobioreactor, to provide a simple structure, easy to manufacture in batches with a specific internal structure that can effectively improve the light energy utilization rate of microalgae scale cultivation The closed photobioreactor can realize the shuttling of algae cells between the light area and the dark area of the photobioreactor, can exert the "flash effect" of algae cells, and improve the light energy utilization rate of microalgae large-scale cultivation .

The closed photobioreactor for improving the light energy utilization rate of microalgae scale cultivation of the present invention:

At least two baffles (as shown in Figure 1) perpendicular to the flow direction of the culture solution are provided on the inner wall of the illuminated surface of the closed photobioreactor, and the area between the baffles is set to cover the cultivation of the photobioreactor. Part or all of the effective illumination surface between the liquid inlet and the outlet (as shown in Fig. 2A, Fig. 2B, Fig. 6A and Fig. 6B).

The closed photobioreactor is a plate photobioreactor, a circular tube photobioreactor, an oval tube photobioreactor and similar or deformed closed photobioreactors.

The length of the baffle in the plate-type photobioreactor is 30%-100% of the width of the culture fluid channel in the plate-type photobioreactor (as shown in FIG. 3 ). The distance between the upper and lower panels of the existing plate-type photobioreactor is generally 10 mm to 100 mm. The supporting ribs are arranged along the flow direction of the culture solution to strengthen the structure of the whole plate photobioreactor, and the ribs are used to separate the flow channels with a width of 10 mm to 300 mm. The length of the flow channel can be adjusted accordingly according to the actual cultivation needs. Ribs can also be used as baffles to connect multiple flow channels in series (as shown in Figure 2A), or to connect multiple flow channels in parallel (as shown in Figure 2B) . In large-scale production, multiple above-mentioned plate-type photobioreactors can be connected in parallel or in series according to the requirements of output, and then matched with other devices.

The baffle plate in the described circular tube type photobioreactor or elliptical tube type photobioreactor is set around the inner wall of circular tube or elliptical tube (as shown in Figure 4), or only in circular tube or elliptical tube The setting of the inner wall surface of the illuminated surface of the tube (as shown in Figure 5, the upper part is the direction of illumination) depends on the convenience during processing; when the baffle is set on the inner wall surface of the illuminated surface of the circular tube, the circular tube photobiological The length (arc length) of the baffle in the reactor is 30%～100% (as shown in Figure 7, the top is the direction of illumination) of the section arc length of the illumination surface of the culture fluid channel; When the inner wall surface of the surface is provided with a baffle, the length (arc length) of the baffle in the elliptical tube type photobioreactor is 30%～100% of the section arc length of the light surface of the culture fluid channel (as shown in Figure 8, above is the light direction). The inner diameter of the circular tube of the existing circular tube photobioreactor or the short diameter of the elliptical tube of the oval tube photobioreactor is 10 mm to 100 mm. The length of the round tube or oval tube can be adjusted accordingly according to the actual culture needs, and can be connected in parallel (as shown in Figure 6A) or in series (as shown in Figure 6B); it can be a straight tube or a plurality of bent tubes. In large-scale production, a plurality of the above-mentioned circular tube photobioreactors or oval tube photobioreactors can be connected in parallel or in series according to the requirement of output, and then matched with other devices.

When using different materials to manufacture the above-mentioned closed photobioreactor with baffles, the manufacturing and installation methods of the above-mentioned baffles can be selected according to the processing performance of the materials. For example, the baffle that has been manufactured separately can be bonded to the inner wall of the closed photobioreactor, the closed photobioreactor and the baffle can be integrally formed with a mold, or the baffle that has been manufactured in advance can be used as a bracket After being connected, it is placed in a closed photobioreactor so that the baffle is close to the inner wall of the closed photobioreactor.

The distance between the baffles is 5mm-50mm.

The height of the baffle (the height of the section of the baffle itself) is 1 mm to 10 mm.

The cross-section of the baffle is in the group consisting of rectangular baffles, trapezoidal baffles, triangular baffles, semicircular baffles and other shapes of baffles (as shown in Figure 10). at least one of .

The thickness of the rectangular baffle is 1mm-5mm.

The thickness at half height of the trapezoidal, triangular or semicircular baffles is 1 mm to 5 mm.

The material for making the baffle can be a light-transmitting material or an opaque material that is easy to process and install, preferably the same material as the light-emitting surface of the photobioreactor.

The light-transmitting material may be one of glass, plexiglass, plastic (polyethylene, polyvinyl chloride, polypropylene, polyester, etc.) and the like. The opaque material may be one of plastic, rubber, resin and the like.

The material of the illuminated surface of described manufacturing closed photobioreactor comprises various light-transmitting materials, as glass, plexiglass, plastics (polyethylene, polyvinyl chloride, polypropylene, polyester etc.), used material can be Sheet, pipe, coil or membrane. These materials can be used to make a hard photobioreactor with a fixed shape, and a soft photobioreactor that can be folded or curled but can be expanded after being filled with culture fluid.

When the culture medium flows through the closed photobioreactor at a certain speed, a vortex will be generated in the baffle area, which will push the algae cells to make approximate circular motions, that is, reciprocating motion in the direction of the light path, so that the algae cells can move in the closed photobioreactor. Shuttle back and forth between the light area and the dark area of the photobioreactor. Algae cells go through a light-dark cycle every cycle (reciprocating once). By adjusting the flow rate of the culture medium, the size of the baffle and the distance between the baffles, different light-dark cycle periods can be obtained, and the frequency of the light-dark cycle can be higher than 1 Hz. Figure 9 shows the change of the position of the particles representing the algae cells in the direction of the light path with time when they move in the vortex. It can be clearly seen that the particles fluctuate regularly in the direction of the light path, and a complete light path The dark cycle period is 100ms ~ 200ms. Since the light attenuates quickly in the culture medium when the algae cells are cultivated at high density, the penetration distance is only about 1 mm, so the height of the baffle does not need to be too high to make the algae cells produce a high-frequency light-dark cycle effect.

The present invention is characterized in that at least two baffles perpendicular to the flow direction of the culture solution are provided on the inner wall of the illuminated surface of the closed photobioreactor, and the closed type of plate type, round tube type, oval tube type and similar or deformed For photobioreactors, as long as the characteristic size of the flow channel (the characteristic size refers to the distance between the upper and lower panels for the plate photobioreactor, that is, the thickness of the flow channel, and for the circular tube photobioreactor, it refers to the inner diameter of the pipe) is in the range of 10mm to 100mm Inside, after the baffle structure of the present invention is added to the inner wall of the illuminated surface, the mixing of the culture solution can be strengthened, and the algae cells can shuttle back and forth between the light area and the dark area.

The closed photobioreactor of the present invention that improves the light energy utilization rate of microalgae scale cultivation can be built outdoors or in a greenhouse to make full use of natural light, and can cultivate various microalgae, including spirulina, salina, Chlorella, diatoms, golden algae, etc.

In the process of actually producing and cultivating algae cells, in addition to the above-mentioned closed photobioreactor of the present invention, the entire culture system is also equipped with a gas-liquid exchange device for gas supply and oxygen analysis (such as adopting CN200810224196.7 method), fluid conveying device, bracket, connection device, material distribution device, and necessary temperature monitoring and control device, and other accessory devices. The connection diagram of the whole culture system is shown in Figure 11.

The advantage of the closed photobioreactor for improving the light energy utilization rate of microalgae scale cultivation of the present invention is that it can give full play to the "flash effect" of algae cells, improve the light energy utilization rate of microalgae scale cultivation, and increase the unit light area. output. In addition, the closed photobioreactor of the present invention that improves the light energy utilization rate of microalgae scale cultivation has a simple structure, is convenient for batch production, and can simply increase the number of reactors to expand the production scale.

Description of drawings

Figure 1. A side view (section) of a closed photobioreactor with baffles of the present invention.

Fig. 2A. Top view of plate-type photobioreactor with baffles of the present invention (channels in series).

Fig. 2B. Top view of the plate-type photobioreactor with baffles of the present invention (flow channels connected in parallel).

Fig. 3. The flow channel end view of the plate-type photobioreactor with baffles of the present invention (in the figure, the length of the baffles is less than the width of the flow channels).

Figure 4. A side view of the tubular photobioreactor with baffles of the present invention (section, the baffles surround the inner wall for a week).

Fig. 5. The side view of the tubular photobioreactor with baffles of the present invention (section, the baffles are only on the inner wall of the illuminated surface).

Fig. 6A. Top view of the tubular photobioreactor with baffles of the present invention (flow channels in parallel).

Fig. 6B. Top view of the tubular photobioreactor with baffles of the present invention (channels in series).

Fig. 7. Flow channel end view of the circular tube type photobioreactor with baffles of the present invention (the baffles are only on the inner wall of the illuminated surface).

Fig. 8. Flow channel end view of the elliptical tubular photobioreactor with baffles of the present invention (the baffles are only on the inner wall of the illuminated surface).

Fig. 9. The position change of algae cells in the light path direction in the plate photobioreactor with baffles of the present invention.

Fig. 10. Schematic diagram of baffles with different cross-sectional shapes and their positions in a closed photobioreactor according to the present invention.

Figure 11. Schematic diagram of the connection of the microalgae culture system.

reference sign

1. Culture solution inlet 2. Culture solution outlet 3. Baffle

4. End panel 5. Rib (baffle) 6. Lower panel (no light)

7. Upper panel (illuminated surface) 8. Culture solution inlet supervisor 9. Round tube or oval tube

10. Culture medium outlet supervisor 11. Pipe connectors

12. Photobioreactor (group) 13. Gas-liquid exchange device

14. Fluid delivery device 15. Temperature control device

15-1. Temperature control instrument 15-2. Temperature sensor 15-3. Heat exchange device

16. Rectangular baffle 17. Trapezoidal baffle 18. Triangular baffle

detailed description

Example 1

Spirulina was cultivated outdoors under natural light. The plate-type photobioreactor of the constructed culture system is placed horizontally, and the manufacturing material is a plexiglass plate, the thickness of the upper and lower panels is 2mm, the thickness of the end panel 4 and the rib plate 5 are both 2mm, and the length of the rib plate 5 is 80cm. The size of the plate-type photobioreactor is: 1m in length, 1.022m in width, and 2cm between the inner surfaces of the upper and lower panels. Adhere to the inner side of the upper panel and paste a baffle 3 with a rectangular cross-section made of plexiglass plate material, the direction of the baffle is perpendicular to the flow channel, the distance between the baffles is 8mm, the height of the baffle is 3mm, and the thickness of the baffle is 2mm. The length of the baffles is 10 cm (equal to the width of the flow channel), and 90 baffles are installed in each flow channel (the area between the baffles covers about 70% of the effective illumination surface of the photobioreactor). The structure of the plate photobioreactor is shown in Figure 2B.

The culture system consists of 10 above-mentioned plate photobioreactors connected in series (divided into two groups, such as middle 12 in Fig. 11 ), gas-liquid exchange device 13, temperature control device 15, and fluid delivery device 14. The connection method is shown in Fig. 11 . The fluid conveying device is a commercially available diaphragm pump, and the culture liquid is driven by the diaphragm pump to circulate in the culture system. The flow rate of the liquid in the above-mentioned plate photobioreactor is 20 cm/s.

The algal species are from the Institute of Process Engineering, Chinese Academy of Sciences, the species is Spirulina Platensis, the medium is Zarrouk medium, and the initial concentration of sodium bicarbonate in the culture medium is 0.1mol/L.

Before culturing, the above-mentioned photobioreactor was washed with water filtered through a 0.2 μ microfiltration membrane. Prepare 200L medium according to Zarrouk medium recipe, and filter the medium with a 0.2μ microfiltration membrane. Prepare the seed solution according to the conventional method, and the inoculation density is 0.1 g/L. The pH value of the culture solution was set at 9.0, the ambient temperature was 25-35°C, and outdoor natural light was used to control the culture temperature at 32±1°C. Samples were taken periodically to determine algal cell density. When the algae cell density reaches 3g (dry weight)/L, semi-continuous harvesting begins. The harvesting method is (about every 3 days) to draw out 20% of the culture solution in the culture system, and return the filtered filtrate to the above-mentioned culture system. The algae cells obtained by filtration are harvested, washed and dried.

During the cultivation period, the concentration of other nutrient salts should be regularly detected and replenished in time, and a small amount of water should be added to make up for the evaporation loss of water. During the cultivation period, a mixed gas of air and carbon dioxide was fed into each gas-liquid exchange device in the culture system, the flow rate of the mixed gas was 0.6L/L.min, and the molar fraction of carbon dioxide in the mixed gas was 3%. The cultivation process continued for 30 days, and the area yield of Spirulina was about 31g/m ² .d, which was higher than the area yield (24g/m ² . .d), indicating that the light energy utilization rate of the algae cells is significantly improved.

Comparative example 1

Spirulina was cultivated under natural light. Other conditions are the same as in Example 1, except that there is no vertical baffle inside the upper panel of the plate-type photobioreactor, which is a plate-type photobioreactor with a conventional structure.

The cultivation process lasted for 30 days, and the area productivity of Spirulina was about 24g/m ² .d.

Example 2

Spirulina was cultivated under natural light. Other conditions were the same as in Example 1, except that the height of the rectangular baffle inside the upper panel of the plate-type photobioreactor was 1 mm, and the distance between the rectangular baffles was 5 mm.

The cultivation process continued for 30 days, and the area productivity of Spirulina was about 33g/m ² .d, which was higher than the area productivity (24g/m ² . .d), indicating that the light energy utilization rate of the algae cells is significantly improved.

Example 3

Spirulina was cultivated under natural light. Other conditions were the same as in Example 1, except that the height of the rectangular baffle inside the upper panel of the plate-type photobioreactor was 8 mm, and the distance between the rectangular baffles was 42 mm.

The cultivation process continued for 30 days, and the area productivity of Spirulina was about 36g/m ² .d, which was higher than the area productivity (24g/m ² . .d), indicating that the light energy utilization rate of the algae cells is significantly improved.

Example 4

Spirulina was cultivated under natural light. Other conditions were the same as in Example 1, except that the distance between the rectangular baffles inside the upper panel of the plate-type photobioreactor was 10 mm.

The cultivation process continued for 30 days, and the area yield of Spirulina was about 40g/m ² .d, which was higher than the area yield (24g/m ² . .d), indicating that the light energy utilization rate of the algae cells is significantly improved.

Example 5

Spirulina was cultivated under natural light. Other conditions are the same as in Example 1, except that the distance between the rectangular baffles inside the upper panel of the plate-type photobioreactor is 20 mm.

The cultivation process continued for 30 days, and the area yield of Spirulina was about 30g/m ² .d, which was higher than the area yield (24g/m ² . .d), indicating that the light energy utilization rate of the algae cells is significantly improved.

Example 6

Spirulina was cultivated under natural light. Other conditions are with embodiment 1, and difference is that the distance of the rectangular baffle plate inboard of the upper panel of plate-type photobioreactor is 10mm, baffle plate length 6cm (accounting for 30% of flow channel width), baffle plate two ends and flow channel Ribs on both sides are installed equidistantly.

The cultivation process continued for 30 days, and the area productivity of Spirulina was about 29g/m ² .d, which was higher than the area productivity (24g/m ² . .d), indicating that the light energy utilization rate of the algae cells is significantly improved.

Example 7

Spirulina was cultivated under natural light. Other conditions are with embodiment 1, and difference is that the distance of the rectangular baffle plate inboard of the upper panel of plate type photobioreactor is 20mm, baffle plate length 14cm (accounting for 70% of flow channel width), baffle plate two ends and flow channel Ribs on both sides are installed equidistantly.

The cultivation process continued for 30 days, and the area productivity of Spirulina was about 27g/m ² .d, which was higher than the area productivity (24g/m ² . .d), indicating that the light energy utilization rate of the algae cells is significantly improved.

Example 8

Other conditions are the same as in Example 1, except that a circular tube photobioreactor is used.

Spirulina was cultivated outdoors under natural light. The circular tubular photobioreactor of the constructed culture system is placed horizontally, and the material is a plexiglass circular tube with a wall thickness of 1 mm, an inner diameter of 5 cm, and a length of 10 m. Every 10 round tubes 9 are arranged side by side, one end is connected with the main pipe 8 of the culture solution inlet, and the other end is connected with the main pipe 10 of the culture solution outlet, forming a group. The annular projection (baffle plate) 3 that protrudes into the circular tube and has a height of 3 mm is formed around the circular tube by means of external hot pressing. The half-height width of the section of the raised (baffle) 3 is 3mm, and the distance of each circle of annular protrusions (baffle) 3 is 20mm. Except for the parts where the connecting pipe fittings are to be installed at both ends of the round tube, the annular protrusions (baffles) cover the entire length of the round tubes, and the number is 490 per round tube (the area between the baffles covers the effective light surface of the photobioreactor of about 98%). The structure of the whole circular tube photobioreactor is shown in Fig. 6A.

The cultivation system consists of 20 parallel tube-type photobioreactors (every 10 constitute a group and are divided into two groups, such as 12 in Figure 11.), gas-liquid exchange device 13, temperature control device 15, fluid delivery device 14 The composition and connection method are shown in Figure 11. The fluid delivery device is a commercially available diaphragm pump, and the flow rate of the culture solution in the circular tube is 20 cm/s.

The volume of the prepared culture medium is about 500L, the control conditions and harvesting method are the same as in Example 1, and the density when harvesting is 5g/L.

During the cultivation period, the concentration of other nutrient salts should be regularly detected and replenished in time, and a small amount of water should be added to make up for the evaporation loss of water. During the cultivation period, a mixed gas of air and carbon dioxide was fed into each gas-liquid exchange device in the culture system, the flow rate of the mixed gas was 1.0L/L.min, and the molar fraction of carbon dioxide in the mixed gas was 3%. The cultivation process continued for 30 days, and the volumetric productivity of Spirulina was about 2.0g/L.d, which was higher than the volumetric productivity (1.5g/L.d ), indicating that the light energy utilization rate of algae cells was significantly improved.

Comparative example 2

Spirulina was cultivated under natural light. Other conditions are the same as in Example 8, except that the inner wall of the circular tube photobioreactor is smooth without protrusions (baffles), that is, a circular tube photobioreactor with a conventional structure.

The culture process lasted for 30 days, and the volumetric productivity of Spirulina was about 1.5g/L.d.

Example 9

Other conditions are the same as in Example 1, except that an elliptical tube photobioreactor is used.

Spirulina was cultivated outdoors under natural light. The elliptical tubular photobioreactor of the constructed culture system is placed horizontally, made of polyethylene hose, the thickness of the tube wall is 0.2mm, the inner diameter after being rounded is 5cm, and the length is 10m. Every 10 round tubes 9 are arranged side by side, one end is connected with the main pipe 8 of the culture solution inlet, and the other end is connected with the main pipe 10 of the culture solution outlet, forming a group. A bulge (baffle) 3 with a height of 2 mm is formed on the upper side of the hose by means of a built-in mold and external hot pressing. The cross-sectional shape of the bulge (baffle) 3 is a triangle 18 (as shown in Figure 10 18), the half-height width of the section of the protrusion (baffle) 3 is 1mm, and the length of the protrusion (baffle) 3 is 4cm (accounting for about 50% of the half circumference of the polyethylene hose), and each protrusion (baffle) Plate) 3 distance is 20mm. Except for the parts where the connecting pipe fittings are to be installed at both ends of the hose, the protrusions (baffles) 3 cover the entire length of the hose, and the number is 490 per hose (the area between the baffles covers the effective light surface of the photobioreactor of about 98%). The structure of the whole circular tube photobioreactor is shown in Fig. 6A.

During actual cultivation, when the culture solution is pumped into the photobioreactor made of polyethylene hose, the hose is stretched into an oval shape with a long diameter (width) of about 6 cm and a short diameter (height) of about 4 cm.

The culture system consists of 20 parallel-connected above-mentioned elliptical tube photobioreactors (every 10 constitute a group and are divided into two groups, such as 12 in Figure 11), gas-liquid exchange device 13, temperature control device 15, fluid delivery device 14 The composition and connection method are shown in Figure 11. The fluid delivery device is a commercially available diaphragm pump, and the flow rate of the culture solution in the oval tube is 20 cm/s.

The volume of the prepared culture medium is about 480L, the control conditions and harvesting method are the same as in Example 1, and the density when harvesting is 5g/L.

During the cultivation period, the concentration of other nutrient salts should be regularly detected and replenished in time, and a small amount of water should be added to make up for the evaporation loss of water. During the cultivation period, a mixed gas of air and carbon dioxide was fed into each gas-liquid exchange device in the culture system, the flow rate of the mixed gas was 1.0L/L.min, and the molar fraction of carbon dioxide in the mixed gas was 3%. The cultivation process continued for 30 days, and the volumetric productivity of Spirulina was about 2.2g/L.d, which was higher than the volumetric productivity (1.7g/L.d ), indicating that the light energy utilization rate of algae cells was significantly improved.

Comparative example 3

Spirulina was cultivated under natural light. Other conditions are the same as in Example 9, except that the inner wall of the elliptical tube photobioreactor is smooth without protrusions (baffles), that is, it is an elliptical tube photobioreactor with a conventional structure.

The culture process lasted for 30 days, and the volumetric productivity of Spirulina was about 1.7g/L.d.

Claims (10)

1. A closed photobioreactor that improves the light energy utilization rate of microalgae scale cultivation is characterized in that: only at least 2 blocks perpendicular to the flow of culture fluid are arranged on the inner wall surface of the illuminated surface of the closed photobioreactor The direction of the baffle, and the area between the baffles is set to cover part or all of the effective illumination surface between the culture solution inlet and the outlet of the photobioreactor; The closed photobioreactor is a horizontal plate photobioreactor, a circular tube photobioreactor or an elliptical tube photobioreactor; The length of the baffle in the plate photobioreactor is 30% to 100% of the width of the culture solution channel in the plate photobioreactor; The length of the baffle in the circular tube photobioreactor or elliptical tube photobioreactor is 30%-100% of the section arc length of the illuminated surface of the culture solution channel. 2. the closed photobioreactor of improving the utilization rate of light energy of microalgae scale cultivation according to claim 1, is characterized in that: in the described circular tube photobioreactor or oval tube photobioreactor The baffle is set around the inner wall of the circular tube or the elliptical tube for a complete circle, or is set only on the inner wall of the illuminated surface of the circular tube or the elliptical tube. 3. The closed photobioreactor according to claim 1 or 2, which improves the light energy utilization rate of microalgae scale cultivation, characterized in that: the baffle plate arranged on the inner wall of the closed photobioreactor , is to bond the baffle that has been manufactured separately to the inner wall of the closed photobioreactor, use a mold to integrally form the closed photobioreactor and the baffle, or connect the prefabricated baffle with a bracket Then put it into the closed photobioreactor so that the baffle is close to the inner wall of the closed photobioreactor. 4. The closed photobioreactor for improving the light energy utilization rate of microalgae scale cultivation according to claim 1 or 2, characterized in that: the distance between the baffles is 5 mm to 50 mm. 5 . The closed photobioreactor for improving light energy utilization efficiency of microalgae scale cultivation according to claim 3 , characterized in that: the distance between the baffles is 5 mm to 50 mm. 6. The closed photobioreactor for improving light energy utilization efficiency of microalgae scale cultivation according to claim 1, 2 or 5, characterized in that: the height of the baffle is 1mm-10mm. 7. The closed photobioreactor for improving the light energy utilization rate of microalgae scale cultivation according to claim 3, characterized in that: the height of the baffle is 1mm-10mm. 8. according to claim 1,2,5 or 7 described closed photobioreactors that improve the utilization rate of light energy of microalgae scale cultivation, it is characterized in that: described baffle plate section is the baffle plate of rectangular shape, At least one selected from the group consisting of trapezoidal-shaped baffles, triangular-shaped baffles, and semicircular-shaped baffles. 9. The closed photobioreactor for improving the light energy utilization rate of microalgae scale cultivation according to claim 8, characterized in that: the thickness of the rectangular-shaped baffle is 1 mm to 5 mm; The thickness at half height of the trapezoidal, triangular or semicircular baffles is 1 mm to 5 mm. 10. according to claim 1,2,5,7 or 9 described closed photobioreactors that improve the light energy utilization rate of microalgae scale cultivation, it is characterized in that: the material of described manufacturing baffle is glass, One of plexiglass, polyethylene, polyvinyl chloride, polypropylene, polyester, rubber.