CN113136344A

CN113136344A - Method and system for mixotrophic-autotrophic co-cultivation of photosynthetic microorganisms and method for production of biomass and bioenergy

Info

Publication number: CN113136344A
Application number: CN202010063029.XA
Authority: CN
Inventors: 朱俊英; 荣峻峰; 程琳; 李煦; 管炳伟; 郄凤翔
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2020-01-19
Filing date: 2020-01-19
Publication date: 2021-07-20

Abstract

The invention relates to the field of microalgae culture, in particular to a method and a system for mixotrophic-autotrophic joint culture of photosynthetic microorganisms and a method for producing biomass and biological energy. The method for culturing photosynthetic microorganisms comprises the following steps: sending the photosynthetic microorganisms to a first reactor for mixotrophic culture under first illumination and first aeration; meanwhile, the photosynthetic microorganisms are sent to a second reactor for autotrophic culture under second illumination and second ventilation; the photosynthetic microorganisms in the two culture stages are the same or different; using the gas discharged from the first reactor as a gas source of part or all of the second aeration; the second reactor is an open or closed photobioreactor. The method of the invention utilizes mixotrophic culture to strengthen autotrophic culture, which is beneficial to culturing microalgae with large scale, low cost and high efficiency.

Description

Method and system for mixotrophic-autotrophic co-cultivation of photosynthetic microorganisms and method for production of biomass and bioenergy

Technical Field

The invention relates to the field of microalgae culture, in particular to a method and a system for mixotrophic-autotrophic joint culture of photosynthetic microorganisms and a method for producing biomass and biological energy.

Background

Microalgae are a group of lower plants which grow in water in a wide variety and distribution, and comprise three culture methods of autotrophic culture, heterotrophic culture and mixotrophic culture. Wherein, the autotrophic culture is mainly to absorb CO through the high-efficiency photosynthesis of microalgae cells₂Converting light energy into chemical energy of carbohydrate such as fat or starch, and releasing O₂. The biological energy and chemicals produced by utilizing microalgae are expected to simultaneously replace fossil energy and reduce CO₂Discharge, etc. Microalgae have received much attention in recent years because of their extremely high production efficiency. The heterotrophic culture is a growth mode utilizing an organic carbon source, the growth rate can be improved by more than ten times or even dozens of times, and the culture is mainly carried out in a fermentation tank. The mixotrophic culture can simultaneously utilize light energy and chemical energy in an organic carbon source for growth and CO₂And an organic carbon source, and the growth rate is higher than that of the autotrophy and the heterotrophy. The photo-energy mixotrophic culture of microalgae, also called mixed nutrient culture, can promote the growth of a plurality of microalgae and the synthesis of protein thereof, and has become a new technology for culturing microalgae due to the advantages of shortening the culture period and realizing high-density culture of cellsHas important significance in production and economy.

The cost is the core problem of microalgae cultivation, organic carbon sources are required in the process of heterotrophic or mixotrophic cultivation of microalgae, and the organic carbon sources are a large part of the cost of the heterotrophic or mixotrophic cultivation of microalgae. In order to reduce the growth cost of microalgae, foreign scholars study the influence of glucose, acetic acid, lactic acid, glycerol, glycine and the like on the growth of the micro-vacant algae, the phaeodactylum tricornutum, the chlorella pyrenoidosa, the spirulina and the like and the accumulation of bioactive substances, and the study result shows that the soluble organic matter with proper concentration is beneficial to the growth of the microalgae and the accumulation of the active substances. Kirrolia et al (Renewable and susteable Energy Reviews 20: 642) compared the costs of microalgae in three different cultivation modes, namely open raceway ponds, photobioreactors and conventional fermenters in 2013, and the comparison showed that the costs of producing oil per unit mass were $ 7.64, $ 24.6 and $ 1.54, and the costs of producing microalgal biomass per unit mass were $ 1.54, $ 7.32 and $ 1.02, respectively. Although organic carbon sources are required to be added for culturing the microalgae in the fermentation tank, the production cost is not increased, which probably is because the microalgae grow in the fermentation tank at high efficiency, the production period of the microalgae is shortened, and other expenses such as labor cost, equipment depreciation cost, land occupation cost and the like for producing the microalgae with unit mass are reduced, thereby reducing the production cost of the microalgae.

Autotrophic and mixotrophic have advantages and problems. The culture by using chemical energy and light energy is mixedly cultured, the speed of accumulating biomass is high, but the biomass quality is also reduced. Although the combined utilization rate of organic carbon source by mixotrophy is higher than that by heterotrophy, a large amount of CO is released₂. While mixotrophic also provides lighting conditions, the effect on improving biomass quality is limited. Autotrophic utilization of free sunlight and absorption of CO₂The conversion of light energy into chemical energy of carbohydrates such as fat or starch is an important culture method.

The information disclosed in the foregoing background section is only for enhancement of background understanding of the invention and to explain the deficiencies of the prior art and may include information that is not prior art.

Disclosure of Invention

One of the purposes of the invention is to enhance the production efficiency of photosynthetic microorganisms and reduce the carbon emission in the process of mixotrophic culture of photosynthetic microorganisms by strengthening the autotrophic process of photosynthetic microorganisms. The other purpose of the invention is to implement autotrophic culture of high-concentration photosynthetic microorganisms and improve the biomass quality of the photosynthetic microorganisms obtained by mixotrophic culture. To this end, the present invention provides a method and system for mixotrophic-autotrophic co-cultivation of photosynthetic microorganisms and a method for production of biomass and bioenergy.

In one aspect, the present invention provides a method for mixotrophic-autotrophic co-cultivation of a photosynthetic microorganism, comprising: sending the photosynthetic microorganisms to a first reactor for mixotrophic culture under first illumination and first aeration; meanwhile, the photosynthetic microorganisms are sent to a second reactor for autotrophic culture under second illumination and second ventilation; the photosynthetic microorganisms in the two culture stages are the same or different; using the gas discharged from the first reactor as a gas source of part or all of the second aeration; the second reactor is an open or closed photobioreactor.

In a second aspect, the present invention provides a system for mixotrophic-autotrophic co-cultivation of photosynthetic microorganisms, the system comprising: the reactor comprises a first reactor for mixotrophic culture of photosynthetic microorganisms and a second reactor for autotrophic culture of photosynthetic microorganisms, wherein the first reactor comprises a first illumination device and a first ventilation device, the second reactor comprises a second illumination device and a second ventilation device, and the second reactor is an open or closed photobioreactor; the gas outlet of the first reactor is communicated with the second ventilating device of the second reactor, so that the gas discharged by the first reactor is used as a gas source of the second ventilating device.

In a third aspect, the present invention provides a method for producing biomass, comprising cultivating a photosynthetic microorganism using the above method, and extracting biomass from the resulting photosynthetic microorganism.

In a fourth aspect, the present invention provides a method for producing a bioenergy source, which comprises cultivating a photosynthetic microorganism using the above method.

The method provided by the invention utilizes mixotrophic culture to strengthen the autotrophic culture process, and is beneficial to culturing photosynthetic microorganisms in a large scale with low cost and high efficiency. In one embodiment of the present invention, autotrophic culture of high-concentration photosynthetic microorganisms can be performed by mixotrophic culture, and the quality of the photosynthetic microorganisms obtained by mixotrophic culture can be improved. In particular, the invention makes it possible to obtain the following advantages:

(1) the invention provides an air source for the autotrophic process by collecting and utilizing the exhaust gas in the mixotrophic process, can strengthen the autotrophic culture process and improve the production efficiency of autotrophic culture; the cost for producing photosynthetic microorganisms can be reduced by using sunlight for autotrophic culture.

(2) The effect of improving the quality of the photosynthetic microorganisms by mixotrophic culture is limited, and the invention provides an air source for the autotrophic process by collecting and utilizing the exhaust gas in the mixotrophic process, so that the autotrophic culture of the photosynthetic microorganisms under high concentration or higher concentration can be implemented, the biomass quality of the photosynthetic microorganisms obtained by mixotrophic culture is obviously improved, the production efficiency of the photosynthetic microorganisms is integrally improved, and the method is beneficial to large-scale, low-cost and high-efficiency production of the photosynthetic microorganisms.

(3) The comprehensive utilization rate of the mixotrophic culture on the organic carbon source is higher than that of the heterotrophic culture, but a large amount of CO is released₂The invention provides the gas source for the autotrophic process by collecting and utilizing the exhaust gas in the mixotrophic process, thereby realizing the discharge of CO in mixotrophic process₂The in-situ biological fixation overcomes the defect of CO in the air₂The content is relatively insufficient, the algae cell autotrophic growth inhibition effect is achieved, the comprehensive utilization rate of the organic carbon source is further improved on the whole, and the carbon emission is reduced.

Drawings

FIG. 1 is a chlorella growth curve of a fermenter according to an example of the present invention.

FIG. 2 is a chlorella growth curve for a tubular reactor in an example of the present invention.

FIG. 3 is a chlorophyll-a/dry weight change curve of chlorella in a fermenter according to an example of the present invention over time.

FIG. 4 is a chlorophyll-a/dry weight change curve of Chlorella in a tubular reactor over time in an example of the present invention.

FIG. 5 is a graph showing the pH change of chlorella in a fermenter according to an example of the present invention with time.

FIG. 6 is a graph of the change in pH over time of chlorella in a tubular reactor in an example of the invention.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The above methods and systems of the present invention will be described concurrently below, but it should be understood that the methods and systems of the present invention can be used in conjunction with each other, or independently as the subject of the present invention.

In the present invention, it is to be understood that the mixotrophic-autotrophic co-culture mode of the present invention is performed simultaneously with the autotrophic culture. The autotrophic photosynthetic microorganism may be the same as or different from the mixotrophic photosynthetic microorganism. Preferably, the autotrophic photosynthetic microorganism is derived from a mixotrophic microorganism, and after the mixotrophic culture is finished, the culture solution part of the mixotrophic culture is sent to a second reactor of the autotrophic culture and cultured in a diluted or undiluted state, and then the rest part of the first culture solution can be continuously mixotrophic cultured in the first reactor (by additionally supplementing nutrient solution), so that when the mixotrophic culture is carried out in the first reactor, the second reactor is simultaneously used for autotrophic culture, the gas discharged from the first reactor can be used as the gas source of the second aeration, and the purposes of strengthening the autotrophic culture process and reducing the discharge of mixotrophic carbon dioxide gas can be achieved. Preferably, a portion of the first broth is sent undiluted to a second reactor; meanwhile, continuing to perform a new round of mixotrophic culture on the rest part of the first culture solution in the first reactor, and circulating in the same way; simultaneously, the aims of improving the quality of the photosynthetic microorganisms obtained by mixotrophic culture and reducing the emission of mixotrophic carbon dioxide are fulfilled. In the invention, the gas discharged from the first reactor is used as a gas source of part or all of the second ventilation gas. The gas discharged from the first reactor may be mixed with a gas for conventional gas supply and then used as a gas source for the second aeration, or may be directly used as the entire gas source for the second aeration without being mixed with other gases.

In the case where the autotrophic photosynthetic microorganisms are derived from mixotrophic microorganisms, the system of the invention preferably comprises: the culture solution outlet of the first reactor is communicated with the algae solution inlet of the second reactor, so that the photosynthetic microorganisms directly enter the second reactor for autotrophic culture after the autotrophic culture in the first reactor.

Wherein the portion of the first culture solution fed to the second reactor accounts for 70 to 90 vol% of the total first culture solution.

In the system, the exhaust port of the first reactor is communicated with the second ventilation device of the second reactor, so that the gas discharged from the first reactor is used as a gas source of the second ventilation device.

Wherein the first reactor is a closed reactor, preferably a fermentation tank structure; the second reactor is not particularly limited, and any photobioreactor suitable for autotrophy may be used in the present invention, which may be open or closed, and is preferably a raceway pond, tubular, plate or column photobioreactor structure.

It should be understood that the mixotrophic culture requires illumination, and therefore the first reactor may be provided with any artificial light source suitable for mixotrophic culture and/or the first reactor may be partially or wholly made of transparent material so that sunlight can be used as the light source.

According to the present invention, the first reactor and the second reactor are communicated with each other through a culture solution transfer pipe, and a transfer pump may be provided on the pipe, or the first reactor may be positioned higher than the second reactor with a sufficient height difference to facilitate transfer of the culture solution from the first reactor to the second reactor.

According to the present invention, the first illumination and the second illumination should adopt illumination intensity suitable for the mixotrophic culture and the autotrophic culture, respectively, and in order to be more suitable for the culture method of the present invention, to obtain higher quality photosynthetic microorganisms, preferably, the illumination intensity of the first illumination is 5000-. Preferably, the illumination intensity of the second illumination is 5000-.

In the invention, the first illumination and the second illumination can adopt sunlight or artificial light. The first illumination is preferably an artificial light source.

According to the present invention, when the diluted first culture solution or microalgae not derived from the first culture solution is subjected to autotrophic culture, the second light is preferably sunlight. In the autotrophic culture of the undiluted first culture medium according to the present invention, the second illumination is preferably an artificial light source.

According to the invention, when the artificial light source is adopted, the illumination wavelength can be changed within a wider range, and can be partial wavelength light or full wavelength light, in order to be more beneficial to the growth of the photosynthetic microorganisms in the invention, preferably, the wavelengths of the first illumination and the second illumination are 380-780nm, more preferably 490-460nm and/or 620-760nm, and under the illumination wavelength, the photosynthetic microorganism cells can better utilize the light energy, and the energy consumption for cultivating the photosynthetic microorganisms is reduced.

The artificial light source used for the illumination can be an LED light source, in particular a blue light and red light LED light source. In order to isolate water vapor, the light source can be sealed by adopting a transparent material.

According to the invention, in order to enable microorganisms to better utilize light energy, for the artificial light source arrangement of the invention, the distance between the artificial light sources in the light direction is preferably 2-300mm, preferably 60-200 mm; or the artificial light source can be directly inserted into the culture solution after being sealed.

In order to be suitable for the mixotrophic culture in the first reactor according to the invention, the first aeration will use an oxygen-containing gas as a source of the first aeration, such oxygen-containing gas may be air, or an oxygen-enriched gas (such as oxygen-enriched air) having an oxygen content greater than that of air. The aeration rate of the first aeration is preferably 0.1-10L/(L.min), preferably 0.2-5L/(L.min), to enable better mixotrophic growth of the photosynthetic microorganisms in the first reactor of the invention.

According to the invention, the gas source used for the second ventilation is the gas discharged by the first reactor or the mixture of the gas discharged by the first reactor and the existing gas (such as air) for autotrophic culture, and the content of the carbon dioxide of the gas is higher than that of the air due to the doping of the carbon dioxide generated in the mixotrophic culture process, thereby being more beneficial to autotrophic culture. Wherein the ventilation rate of the second ventilation is preferably 0.1-10L/(L.min), more preferably 0.2-5L/(L.min).

According to the present invention, the aeration device used for the first aeration and the second aeration may be an aeration device structure conventionally used in the art as long as it can be used for performing the first aeration and the second aeration of the present invention.

According to the invention, the mixotrophic culture can be carried out under stirring, wherein the stirring speed is preferably 200-500 r/min. For this purpose, a stirring structure may be added to the first reactor of the system of the present invention.

According to the present invention, it is preferable that the temperature of the mixotrophic culture is 20 to 35 ℃. The cultivation time may vary within wide limits, for example from 3 to 10 days. The term "mixotrophic culture" as used herein means a time period from the start of culture to the harvest of the photosynthetic microorganisms, and also means a time period from the start of culture to the re-feeding to the second reactor for autotrophic culture.

According to the present invention, the temperature of the autotrophic culture is preferably 20-35 ℃. The incubation time may vary within wide limits, for example from 3 to 20 days. The autotrophic cultivation time is understood to mean both the cultivation time of the photosynthetic microorganisms per batch and the residence time of the photosynthetic microorganisms in the second reactor of the autotrophic cultivation. That is, the culture solution of the autotrophic culture may be continuously discharged out of the second reactor at a certain flow rate.

According to the present invention, preferably, the photosynthetic microorganism is a microalgae, preferably a green alga, more preferably a chlorella.

According to the present invention, the first reactor of the present invention is hermetically sealed, so that a sterile mixotrophic culture, which requires the supplementation of an organic carbon source, can be performed. Preferably, the organic carbon source is a saccharide and/or an acetate. The saccharide may be one or more of glucose, fructose, sucrose, maltose, and the like. The solvent may be, for example, sodium acetate. More preferably, the organic carbon source is glucose.

Wherein the amount of the organic carbon source added may vary within a wide range, and preferably, the amount of the organic carbon source added in the culture system is 5 to 15 g/L.

According to the invention, the mixotrophic culture system of the photosynthetic microorganisms may also be supplemented with other agents conventionally used in the art, such as phosphate (e.g. K)₂HPO₄、Na₂HPO₄Etc.). They may be used in amounts conventional in the art, and the present invention is not particularly limited thereto.

According to the present invention, in order to maintain a constant sterile environment for mixotrophic culture, the gas used for aeration may be sterile, and antibiotics may be added to the mixotrophic culture system to prevent bacterial growth. Such antibiotics may be those conventionally employed in the art for controlling the aseptic culture of microorganisms, and may be, for example, one or more of kanamycin, chloramphenicol, streptomycin, gentamicin, vancomycin, azithromycin, and the like. The amount may vary within wide limits, for example from 10 to 65 mg/L.

According to the invention, the culture medium adopted by the culture system of the photosynthetic microorganism preferably consists of: k₂HPO₄·3H₂O：20-50mg/L，NaNO₃：1200-2000mg/L，Na₂CO₃：10-30mg/L，MgSO₄·7H₂O：50-90mg/L，CaCl₂·2H₂O: 30-50mg/L, citric acid: 1-10mg/L, ferric ammonium citrate: 1-10mg/L, sodium EDTA: 0.5-2mg/L, trace element A5: 0.5-2 ml/L.

The composition of the trace element A5 is preferably as follows: h₃BO₃：2500-3000mg/L，MnCl₂·4H₂O：1500-2000mg/L，ZnSO₄·7H₂O：200-250mg/L，CuSO₄·5H₂O：50-90mg/L，NaMoO₄·5H₂O：350-420mg/L，Co(NO₃)₂·6H₂O：20-65mg/L。

The biomass may be any of a variety of biomass conventional in the art, for example, may be one of a lipid, a protein, a carbohydrate, a nucleic acid, a pigment, a vitamin, a growth factor, or any combination thereof.

The method is suitable for the culture of photosynthetic microorganisms, and can obtain high-quality photosynthetic microorganism fermentation liquor with higher yield under lower energy consumption.

The present invention will be described in detail below by way of examples.

In the following examples:

and (3) measuring the dry weight of the chlorella: taking an appropriate amount of algae liquid, 6000r/min, centrifuging for 5min, removing supernatant, freeze-drying algae mud for 72h, and weighing.

Chlorella species are from the institute for aquatic organisms, academy of sciences, China. And an alga seed preparation stage, namely adding about 600mL of BG11 culture medium and 5g/L of glucose into a triangular flask, then sterilizing at 120 ℃ for 30min, cooling, adding a proper amount of alga seeds and 50mg/L of kanamycin, and then introducing sterile air to culture for about 3d under the conditions that the light intensity is 6000lux and the temperature is 28 ℃ to obtain induced alga seeds.

BG11 medium composition: k₂HPO₄·3H₂O：40mg/L，NaNO₃：1500mg/L，Na₂CO₃：20mg/L，MgSO₄·7H₂O：75mg/L，CaCl₂·2H₂O: 36mg/L, citric acid: 6mg/L, ferric ammonium citrate: 6mg/L, sodium EDTA: 1mg/L, trace element A5: 1 ml/L.

Composition of trace element a 5: h₃BO₃：2860mg/L，MnCl₂·4H₂O：1810mg/L，ZnSO₄·7H₂O：222mg/L，CuSO₄·5H₂O：79mg/L，NaMoO₄·5H₂O：390mg/L，Co(NO₃)₂·6H₂O：50mg/L。

A culture system: the culture system comprises a first reactor and a second reactor which are sequentially connected in series, wherein the first reactor is a closed fermentation tank with the volume of 5L, and the second reactor is an open tubular photobioreactor with the volume of 10L; wherein, the algae liquid outlet of the bottom of the closed fermentation tank is connected with an algae liquid conveying pipe, the algae liquid conveying pipe is connected to a conveying pump, and the outlet of the conveying pump is connected to an algae liquid inlet at the upper part of the open tubular photobioreactor through another algae liquid conveying pipe; the top exhaust port of the closed fermentation tank is connected to the air inlet of the aeration device in the open tubular photobioreactor through an air conveying pipe.

Example 1

This example is intended to illustrate the method for culturing a photosynthetic microorganism of the present invention.

Adding 3L BG11 culture medium and 15g/L glucose into a closed fermentation tank of the culture system, sterilizing at 120 deg.C for 30min, cooling, inoculating with glucose-induced chlorella strain and 50mg/L kanamycin, introducing 0.5L/(L.min) sterile air at 28 deg.C, 250r/min rotation speed, 10000lux light intensity, 380 and 780nm illumination wavelength, and 12h light-dark period: and (4) 12 h. Supplementing 15g/L glucose every day, supplementing other nutrient salts according to consumption, and performing mixotrophic culture until the growth of algae cells is slow.

80 volume percent of algae liquid from a closed fermentation tank is directly transferred to an open tubular photobioreactor without dilution for autotrophic culture, the culture temperature is 28 ℃, the illumination intensity is 20000lux, and the illumination wavelength is 380-780 nm. Meanwhile, 2.4L of BG11 culture medium, 10g/L of glucose and 50mg/L of kanamycin which are sterilized are continuously added into the closed fermentation tank, the nutrition is supplemented every day, and the remaining part of algae liquid is taken as algae seeds to be continuously cultured in the closed fermentation tank mixedly.

Introducing gas discharged from an exhaust port of the closed fermentation tank into a bottom gas inlet of the open tubular photobioreactor, ventilating the tubular photobioreactor, and keeping the ventilation flow at 1L/(L.min); meanwhile, the gas discharged from the exhaust port of the tubular photobioreactor is directly discharged, and the closed fermentation tank is aerated by pure compressed air, so that the aeration flow is kept at 1L/(L.min).

The dry weight, chlorophyll a/dry weight (weight ratio) and pH of chlorella in the fermentor and tubular photobioreactor were measured at the designated time under simultaneous mixotrophic and autotrophic culture as shown in tables 1, 2 and 3, respectively.

Example 2

Adding 3L BG11 culture medium and 15g/L glucose into a closed fermentation tank of the culture system, sterilizing at 120 deg.C for 30min, cooling, inoculating, adding glucose-induced chlorella strain and 10mg/L chloramphenicol, introducing 0.8L/(L.min) sterile air at 28 deg.C, 250r/min, 8000lux light intensity, and 380 and 780nm illumination wavelength, supplementing nutrition every day, and continuing mixotrophic culture in the closed fermentation tank with the rest of the strain solution as the strain. 80 volume percent of algae liquid from the closed fermentation tank is directly transferred to an open tubular photobioreactor without dilution for autotrophic culture, the culture temperature is 28 ℃, the illumination intensity is 15000lux, and the illumination wavelength is 380-780 nm. Meanwhile, the sterilized 3L BG11 culture medium, 15g/L glucose and 10mg/L chloramphenicol are continuously added into the closed fermentation tank, and the light-dark period is 12 h: and (4) 12 h. Supplementing 15g/L glucose every day, supplementing other nutrient salts according to consumption, and performing mixotrophic culture until the growth of algae cells is slow.

Introducing gas discharged from an exhaust port of the closed fermentation tank into a bottom gas inlet of the open tubular photobioreactor, ventilating the tubular photobioreactor, and keeping the flow rate of ventilation at 0.8L/(L.min); meanwhile, the gas discharged from the exhaust port of the tubular photobioreactor is directly discharged, and the closed fermentation tank is aerated by pure compressed air, so that the aeration flow is kept at 0.8L/(L.min).

Example 3

The method as described in example 1, except that, when the mixotrophic culture and the autotrophic culture are performed simultaneously, the light intensity for the mixotrophic culture is 5000lux and the light intensity for the autotrophic culture is 8000 lux; the dry weight, chlorophyll a/dry weight (weight ratio) and pH of chlorella in the fermentor and tubular photobioreactor were measured at the designated time under simultaneous mixotrophic and autotrophic culture as shown in tables 1, 2 and 3, respectively.

Example 4

According to the method described in example 1, except that when the mixotrophic culture and the autotrophic culture are performed simultaneously, the light intensity for the autotrophic culture is 40000 lux; the dry weight, chlorophyll a/dry weight (weight ratio) and pH of chlorella in the fermentor and tubular photobioreactor were measured at the designated time under simultaneous mixotrophic and autotrophic culture as shown in tables 1, 2 and 3, respectively.

Example 5

The method according to example 1, except that, when the mixotrophic culture and the autotrophic culture are performed simultaneously, the illumination wavelength for the mixotrophic culture and the autotrophic culture is the full wavelength; the dry weight, chlorophyll a/dry weight (weight ratio) and pH of chlorella in the fermentor and tubular photobioreactor were measured at the designated time under simultaneous mixotrophic and autotrophic culture as shown in tables 1, 2 and 3, respectively.

Comparative example 1

According to the method described in example 1, except that the mixotrophic culture and the autotrophic culture are performed simultaneously, air is introduced into the tubular photobioreactor instead of the gas discharged from the fermentor; the dry weight, chlorophyll a/dry weight (weight ratio) and pH of chlorella in the fermentor and tubular photobioreactor were measured at the designated time under simultaneous mixotrophic and autotrophic culture as shown in tables 1, 2 and 3, respectively.

TABLE 1

TABLE 2

TABLE 3

The change of the dry weight of the chlorella in the fermenter in table 1 with time is plotted as a chlorella growth curve shown in fig. 1, and the change of the dry weight of the chlorella in the tubular reactor in table 1 with time is plotted as a chlorella growth curve shown in fig. 2; plotting the chlorophyll a/dry weight values over time for the chlorella in the fermentor of table 2 as the curve shown in fig. 3, and plotting the chlorophyll a/dry weight values over time for the chlorella in the tubular reactor of table 2 as the curve shown in fig. 4; the pH of the chlorella over time in the fermentor shown in Table 3 is plotted as shown in FIG. 5, and the pH of the chlorella over time in the tubular reactor shown in Table 3 is plotted as shown in FIG. 6.

As can be seen from the results shown in the table and the figure, the method of the invention strengthens the autotrophic culture process of the microalgae, thereby realizing the production of CO by mixotrophy₂In situ biological fixation; meanwhile, the invention can also implement autotrophic culture of high-concentration microalgae, thereby obviously improving the quality of the mixotrophic microalgae biomass.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A method of mixotrophic-autotrophic co-cultivation of photosynthetic microorganisms, the method comprising: sending the photosynthetic microorganisms to a first reactor for mixotrophic culture under first illumination and first aeration; meanwhile, the photosynthetic microorganisms are sent to a second reactor for autotrophic culture under second illumination and second ventilation; the photosynthetic microorganisms in the two culture stages are the same or different; using the gas discharged from the first reactor as a gas source of part or all of the second aeration; the second reactor is an open or closed photobioreactor.

2. The method according to claim 1, wherein a part of the first culture liquid is sent to a second reactor and cultured in a diluted or undiluted state; meanwhile, continuing to perform a new round of mixotrophic culture on the rest part of the first culture solution in the first reactor, and circulating in the same way;

preferably, the ventilation volume of the first ventilation is 0.1-10L/(L.min), preferably 0.2-5L/(L.min); the first aeration adopts oxygen-containing gas, and the oxygen-containing gas is air or oxygen-enriched air.

3. The method according to claim 1 or 2, wherein the second aeration has an aeration volume of 0.1-10L/(L-min), preferably 0.2-5L/(L-min).

4. The method according to any one of claims 1-3, wherein the intensity of the first illumination is 5000-;

the illumination intensity of the second illumination is 5000-.

5. The method according to any one of claims 1 to 4, wherein the temperature of the mixotrophic culture is 20-35 ℃;

the temperature of the autotrophic culture is 20-35 ℃.

6. Method according to any one of claims 1-5, wherein the photosynthetic microorganism is a microalgae, preferably a green algae, more preferably a chlorella.

7. A system for mixotrophic-autotrophic co-cultivation of photosynthetic microorganisms, the system comprising: the reactor comprises a first reactor for mixotrophic culture of photosynthetic microorganisms and a second reactor for autotrophic culture of photosynthetic microorganisms, wherein the first reactor comprises a first illumination device and a first ventilation device, the second reactor comprises a second illumination device and a second ventilation device, and the second reactor is an open or closed photobioreactor; the gas outlet of the first reactor is communicated with the second ventilating device of the second reactor, so that the gas discharged by the first reactor is used as a gas source of the second ventilating device;

preferably, the culture solution outlet of the first reactor is communicated with the algae solution inlet of the second reactor, so that the photosynthetic microorganisms directly enter the second reactor for autotrophic culture after the mixotrophic culture in the first reactor.

8. The system of claim 7, wherein the first reactor is a fermentor structure; the second reactor is in a raceway pond, tubular, plate or column type photobioreactor structure.

9. A method for producing biomass, comprising cultivating a photosynthetic microorganism according to the method of any one of claims 1 to 6, and extracting biomass from the resulting photosynthetic microorganism.

10. A method of producing a bioenergy source, comprising culturing a photosynthetic microorganism using the method of any one of claims 1 to 6.