Method and system for improving algal oil yield based on circadian rhythm light regulation and control

Abstract

The invention provides a method and a system for improving algal oil yield based on circadian rhythm light regulation and control, and belongs to the technical field of algal oil production, and the method comprises the following steps: a first illumination program: the ratio of light to dark of an illumination period is (12: 12)-(20: 4); after the concentration of the indication nutritional factors in the culture medium is consumed to a set threshold value, switching to a second illumination program: the ratio of brightness to darkness of an illumination period is (6: 18)-(10: 14), and carrying out illumination by adopting ultra-high-light-intensity pulsed light and medium-low-light-intensity recovery light alternately and circularly; and after the content of the grease in the culture medium enters the plateau stage, switching to a third illumination procedure: the ratio of light to dark in the illumination period is (4: 20)-(8: 16), culturing for 12-48 hours, and then harvesting the grease. The invention provides a multi-stage dynamic light regulation and control strategy matched with the growth stage and the internal circadian rhythm of microorganisms, efficient cooperation of biomass accumulation and grease synthesis is realized, the tradeoff relation between growth and grease accumulation in the traditional technology is finally broken through, and the illumination energy consumption is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of bacterial and algal oil production technology, specifically to a method and system for improving bacterial and algal oil yield based on diurnal circadian light regulation. Background Technology

[0002] Single-cell oil (SCO) is an ideal sustainable feedstock for producing third-generation biodiesel. Among them, microalgae are considered the most promising producers due to their high photosynthetic efficiency, high oil content, and lack of competition with humans for food. Currently, conventional technologies to improve microalgal oil yield mainly include nutrient stress (such as nitrogen limitation), genetic metabolic engineering, and optimization of culture process parameters (such as pH and temperature). However, these technologies have significant bottlenecks. While nutrient stress can increase oil content, it often comes at the cost of biomass, resulting in limited overall oil yield. More importantly, the regulation strategy of light, as the most important environmental factor for photoautotrophic microorganisms, is far from optimized. Most current photobioreactors use constant light or simple fixed-cycle light (such as 12h:12h), a crude approach that ignores the deep regulatory mechanisms of light on microbial physiological metabolism. Summary of the Invention

[0003] In view of the technical problems existing in the background art, this application provides a method for improving the oil yield of bacteria and algae based on diurnal light regulation, aiming to solve the technical problem of low oil yield of existing microalgae.

[0004] In a first aspect, embodiments of this application provide a method for improving the oil yield of bacteria and algae based on diurnal light regulation, comprising the following steps: inoculating oil-producing microorganisms into a culture medium, and sequentially inducing the oil-producing microorganisms to produce oil using a first light program, a second light program, and a third light program; The first illumination program has a light-to-dark ratio of (12:12) to (20:4) and a red-rich light to red-blue light intensity ratio of (5:1) to (9:1) in the spectrum. After the concentration of the indicator nutrient factor in the culture medium is consumed to the set threshold, the second light program is switched: the light:dark ratio of the light cycle is (6:18)~(10:14), and ultra-high intensity pulsed light and medium-low intensity recovery light are used alternately for illumination. The intensity ratio of blue-rich light to red-blue light in the spectrum is (1:1)~(3:1). After the oil content in the culture medium reaches a plateau, switch to the third light program: the light-to-dark ratio of the light cycle is (4:20)~(8:16), the intensity ratio of red-rich light to red-blue light in the spectrum is (5:1)~(9:1), and harvest the oil after 12~48h of culture.

[0005] Secondly, this application provides a system for improving the yield of bacterial and algal oils based on diurnal light regulation, used to execute the above-mentioned method for improving the yield of bacterial and algal oils based on diurnal light regulation. The system includes a photobioreactor, a light source module, a sensor module, and a control center. The culture medium is located inside the photobioreactor. The light source module and the sensor module are installed inside the bioreactor. The light source module includes several red LED units and several blue LED units. The light intensity and spectrum of the red LED units and blue LED units can be modulated by the control center. The sensor is signal-connected to the control center and includes a photometric sensor.

[0006] The advantages of this application, which differ from existing technical solutions, include: 1. This invention provides a multi-stage dynamic light regulation strategy that matches the growth stages and intrinsic diurnal rhythms of microorganisms. The microbial culture process is divided into three specific stages: a high biomass proliferation phase (first light program), a lipid-induced accumulation phase (second light program), and a lipid maturation maintenance phase (third light program). Distinctly different light strategies are applied to each stage, rather than a single fixed light pattern. During the high biomass proliferation phase, a "long day cycle" is used to promote bacterial and algal growth. During the lipid-induced accumulation phase, a lighting pattern combining a "short day cycle" and "non-constant pulsed light intensity during the light period" is used to induce lipid accumulation. Through this phased strategy of "promoting growth first, then inducing accumulation," biomass and lipid content are synergistically optimized, achieving a significant increase in lipid yield per unit volume.

[0007] 2. The dynamic light control (especially pulsed light) used in this invention can significantly reduce total energy consumption and production costs compared to continuous high-intensity light.

[0008] 3. This invention utilizes a dynamic combination of spectrum and photoperiod to precisely regulate metabolic flow at the level of signal transduction and gene expression, resulting in a more fundamental and efficient mechanism of action.

[0009] 4. This invention provides a circadian rhythm light regulation system, which integrates online monitoring and feedback control, realizing refined and automated management of the cultivation process and is easy to scale up industrially.

[0010] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Detailed Implementation

[0011] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0012] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0013] Recent studies have revealed that, similar to higher plants, microalgae possess an intrinsic circadian rhythm system (biological clock). This system predicts and adapts to the photoperiodic changes of day and night, thereby optimizing their photosynthesis, cell division, and metabolic pathways. Although existing technologies recognize the importance of photoperiod, how to dynamically and synergistically regulate photoperiod, light intensity, and spectrum, and precisely couple them with the growth stages and intrinsic biological clock of microorganisms to maximize lipid yield remains an underexplored area. This invention aims to fill this gap by systematically addressing the aforementioned problems through an innovative, staged, dynamic light regulation strategy.

[0014] To address the technical problem of low lipid yield in existing microalgae, this application provides a system for improving lipid yield in bacteria and algae based on diurnal circadian light regulation. This invention provides a multi-stage dynamic light regulation strategy that matches the microbial growth stage and intrinsic diurnal rhythm, achieving efficient synergy between biomass accumulation and lipid synthesis, ultimately breaking through the trade-off between growth and lipid accumulation in traditional technologies, and significantly reducing light energy consumption.

[0015] In a first aspect, embodiments of this application provide a method for improving the oil yield of bacteria and algae based on diurnal light regulation, comprising the following steps: inoculating oil-producing microorganisms into a culture medium, and sequentially inducing the oil-producing microorganisms to produce oil using a first light program, a second light program, and a third light program; The first illumination program has a light-to-dark ratio of (12:12) to (20:4) and a red-rich light to red-blue light intensity ratio of (5:1) to (9:1) in the spectrum. After the concentration of the indicator nutrient factor in the culture medium is consumed to the set threshold, the second light program is switched: the light:dark ratio of the light cycle is (6:18)~(10:14), and ultra-high intensity pulsed light and medium-low intensity recovery light are used alternately for illumination. The intensity ratio of blue-rich light to red-blue light in the spectrum is (1:1)~(3:1). After the oil content in the culture medium reaches a plateau, switch to the third light program: the light-to-dark ratio of the light cycle is (4:20)~(8:16), the intensity ratio of red-rich light to red-blue light in the spectrum is (5:1)~(9:1), and harvest the oil after 12~48h of culture.

[0016] In the technical solution of this application embodiment, the light cycle in the first lighting program is light:dark = 12:12 ~ 20:4, which is a "long-day" or near-continuous light pattern. The long light period provides ample time for photosynthesis, ensuring that cells can continuously fix CO2, produce large amounts of ATP and NADPH, and synthesize precursors needed to build cell structures (such as proteins, nucleic acids, and cell walls). The shorter dark period limits cellular respiration and sets the circadian rhythm in the "growth and division" phase. This is similar to the natural conditions of spring and early summer, where plants prioritize vegetative growth.

[0017] Light intensity between 200 and 600 μmol / m 2 / s offers the following advantages: It utilizes a continuous medium-to-high light intensity. This light intensity range is sufficient to reach or approach the light saturation point of many microalgae, driving high-rate photosynthesis and providing ample energy and reducing power for rapid cell division. Its aim is to maximize photosynthetic efficiency rather than stress the cells, ensuring they are in optimal growth condition.

[0018] A red-to-blue light ratio of 5:1 to 9:1 is considered red-rich, offering the following benefits: Maximized photosynthetic efficiency: The reaction centers of Photosynthetic System II (PSII) and chlorophyll a / b exhibit strong absorption peaks for red light (600-700 nm). Enriching red light directly and efficiently drives the light-dependent reactions, producing ATP and NADPH, providing the power for carbon fixation and assimilation. Promoted cell elongation and division: In plants and some microalgae, red light signals are sensed through the phytochrome system and are typically associated with promoting cell elongation and division and inhibiting shading responses, which is beneficial for rapid biomass accumulation. Optimized energy efficiency: The electro-optical conversion efficiency of red LEDs is generally higher than that of blue light. During growth stages requiring high-intensity light, using a red-rich spectrum helps reduce system energy consumption.

[0019] The second lighting program, with a light-to-dark cycle of 6:18 to 10:14, offers the following benefits: This is a "short-day" pattern. A long dark period is a strong environmental signal, interpreted by the cell's circadian rhythm system as the approach of an "unfavorable season (such as autumn and winter)." This signal downregulates the expression of genes related to cell division while upregulating the expression of genes related to energy storage (i.e., lipid synthesis). Cellular metabolism shifts entirely from "investing in new cells" (growth) to "storing energy for survival" (lipid synthesis).

[0020] The light intensity mode (ultra-high intensity pulsed light + medium-low intensity recovery light) has the following advantages: creating "energy surplus": brief ultra-high light intensity (200~600 μmol / m²). 2 The photoreaction rate reaches its peak instantaneously at / s, producing ATP and NADPH far exceeding the instantaneous demand for carbon fixation. To avoid photodamage, cells must find a way to dispose of this excess energy and reducing power. Lipid synthesis, an extremely energy-intensive (ATP) and reducing power-intensive (NADPH) process, becomes the perfect "drainage channel" for this excess energy.

[0021] Avoiding light suppression and improving energy efficiency: The subsequent recovery period at medium to low light intensity (100-400 μmol / m 2 The pulse pattern of light intensity ( / s) allows the photosynthetic apparatus to "rest," preventing a decrease in photosynthetic efficiency (photoinhibition) caused by continuous high light intensity. This "burst-rest" pulse pattern can achieve higher energy conversion efficiency in lipid synthesis with lower overall light energy input, resulting in significant energy savings.

[0022] A red-to-blue light ratio of 1:1 to 3:1 indicates blue light richness, which offers the following benefits: Activation of stress and reserve signals: Blue light is sensed by specific photoreceptors (such as cryptochrome and phototropin), pathways that are typically closely related to stress responses, metabolic reprogramming, and inhibition of cell elongation. Blue light richness signals synergistically work with short-day signals to further reinforce the metabolic command to "stop growth and begin fat storage." Regulation of key lipid synthesis enzymes: Studies have shown that blue light can specifically regulate the expression of genes related to certain key lipid synthesis enzymes (such as acetyl-CoA carboxylase), directly driving carbon flow to lipids from key nodes in the metabolic network.

[0023] The third light program, with a light:dark cycle of 4:20 to 8:16, offers the following benefits: This is an extreme short-day or near-continuous dark pattern. Its purpose is no longer to promote synthesis, but rather to create a "dormant" or "maintenance" state. The extremely long dark period strongly inhibits any activity related to growth or active metabolism, while simultaneously maintaining a "reserve mode" signaling to prevent cells from using synthesized lipids as substrates for respiration or converting them into other substances, thus "locking in" the achieved lipid yield.

[0024] Light intensity is 20~100 μmol / m 2 The advantages of using light at extremely low intensity or even complete darkness are as follows: Cell density is high, and lipid content has reached its peak, eliminating the need for and providing the conditions for high-intensity photosynthesis. The extremely low light intensity is used only to maintain basic cellular metabolic activity, preventing cell death and degradation. Its main benefit is reducing light energy consumption to extremely low levels, significantly improving the economic efficiency of the entire process from both engineering and economic perspectives.

[0025] A red-to-blue light ratio of 5:1 to 9:1 indicates red light enrichment, offering the following advantages: Maximized energy efficiency: Similar to the first stage, when limited light energy is required, red light, with the highest photosynthetic efficiency, is used to maintain cell activity with minimal energy input. Potential maturation-promoting effect: Studies suggest that red light may be beneficial for the maturation and stability of lipid bodies. More importantly, it avoids unnecessary stress or metabolic activation signals that blue light might activate, allowing cells to await harvest in a "quiet," low-energy state.

[0026] Furthermore, in some embodiments, the intensity of the ultra-high intensity pulsed light in the second illumination procedure is 200~600 μmol / m². 2 / s, illumination time is 5~30min; The intensity of the recovery light at medium and low intensity is 100~400 μmol / m 2 / s, with an illumination time of 20~60min.

[0027] In the technical solution of this application embodiment, in the second illumination program, an illumination mode combining "short day cycle" and "non-constant pulse light intensity during the day period" is adopted to induce oil accumulation.

[0028] Short days (long dark periods) are a strong environmental signal, similar to the seasonal transition to autumn and winter in nature. This signal is received and interpreted by the microbial circadian rhythm system (biological clock). The biological clock system regulates the periodic expression of a large number of downstream genes.

[0029] During the first photoperiod of "long-day" conditions (high biomass proliferation phase), cells primarily use the absorbed carbon and energy to build proteins, nucleic acids, and other substances necessary for cell division and growth. When switching to "short-day" conditions, coupled with the depletion of nutrients (such as nitrogen) in the culture medium, cells interpret this as an impending unfavorable growth season. At this time, the biological clock and nutrient stress signals work synergistically, downregulating the expression of genes related to cell division and growth while upregulating genes related to energy reserves and stress responses. This leads to a sudden increase in light capture and electron transport chain rates: Under brief periods of extremely high light intensity, the photosynthetic system is fully activated, and the photochemical reaction rate reaches its peak, producing far more ATP and NADPH than the instantaneous requirements of the dark reaction. This excess ATP and NADPH cannot be immediately and completely consumed by the Calvin cycle. To avoid photo-oxidative damage caused by reactive oxygen species, cells must find ways to "release" this excess energy and reducing power.

[0030] After extremely high light intensity, switching to medium to low light intensity allows the photosynthetic system to "rest," preventing damage to photosynthetic structures caused by continuous high light intensity and maintaining cellular health. During the recovery period, the levels of ATP and NADPH produced by the light reaction are more aligned with the needs of the Calvin cycle, ensuring stable carbon fixation.

[0031] Lipid synthesis is a highly energy-intensive (requiring large amounts of ATP) and highly reducing (requiring large amounts of NADPH) process. The periodic "energy surplus" state created by pulsed light provides the ideal power source for lipid synthesis. The excess ATP and NADPH are preferentially used to reduce and esterify previously fixed carbons (such as pyruvate and acetyl-CoA) into triglycerides. This nested "light-dark" microcycle (on a minute scale) and "short-day" macrocycle (on an hour scale) ensures that light energy is converted into chemical energy with almost no waste and precisely "invested" in lipids, a high-value energy storage product.

[0032] Blue light receptors (such as cryptochrome and phototropin) are important components for sensing light quality and photoperiod. Using a blue-rich spectrum (blue light: red-blue light = 1:1 to 3:1) in the second lighting program can specifically activate the blue light signaling pathway, which is usually closely related to processes such as stress response and metabolic reprogramming.

[0033] In synergy with short-day signals, it further inhibits cell division activity and enhances the expression of genes related to key enzymes in lipid synthesis (such as acetyl-CoA carboxylase ACC and diacylglycerol acyltransferase DGAT), thereby driving carbon flow to lipid synthesis from key nodes of the metabolic network.

[0034] Furthermore, in some embodiments, the light intensity in the first illumination procedure is 200~600 μmol / m². 2 / s.

[0035] Furthermore, in some embodiments, the light intensity in the third illumination procedure is 20~100 μmol / m². 2 / s.

[0036] Furthermore, in some embodiments, the temperature during the cultivation of oil-producing microorganisms is 25±1℃, and air containing 1%~5% CO2 is introduced into the culture medium.

[0037] Furthermore, in some embodiments, the oil-producing microorganisms include microalgae and oil-producing yeasts.

[0038] Furthermore, in some embodiments, the microalgae include at least one of the genera Chlorella, Scenedesmus, and Brown finger algae.

[0039] Furthermore, in some embodiments, the oil-producing yeast includes at least one of Rhodotorula glutinis and Rhodotorula spp.

[0040] Furthermore, in some embodiments, the culture medium includes at least one of BG-11 medium and YPD medium.

[0041] Furthermore, in some embodiments, the indicator nutrient factor includes at least one of nitrogen source, phosphorus source, and sulfur source, with a threshold value set at 5% to 20%.

[0042] In the technical solution of this application embodiment, the threshold is set within the aforementioned range to obtain the highest overall lipid yield. If the nutrient concentration is too high (e.g., >30%), the process is switched. At this time, the cells are still in a vigorous growth phase, and prematurely introducing stress signals (e.g., short-day light, blue light rich light) will prematurely inhibit cell division, resulting in insufficient biomass. Although the percentage of lipid content may not be low at this time, the overall lipid yield (lipid yield = biomass × lipid content) will be limited due to the low biomass.

[0043] If the switch is delayed until nutrients are almost completely depleted (e.g., <5%), cells will be subjected to deep and severe nutritional stress. This can lead to severe growth arrest and decreased cell activity, and may even trigger programmed cell death. Carbon flow is diverted to other secondary metabolites (such as starch and pigments) instead of lipids. In an attempt to save themselves, cells may break down already synthesized lipids again (lipolysis) for energy, resulting in a decrease in lipid yield instead of an increase.

[0044] Furthermore, in some embodiments, in the second illumination program, if the growth rate of the oil content in the culture medium is less than 5% for 24-48 hours, it is determined to have entered the plateau phase; otherwise, it has not entered the plateau phase.

[0045] Secondly, embodiments of this application provide a system for improving the yield of bacterial and algal oils based on diurnal light regulation, used to execute the above-mentioned method for improving the yield of bacterial and algal oils based on diurnal light regulation. The system includes a photobioreactor, a light source module, a sensor module, and a control center. The culture medium is located inside the photobioreactor. The light source module and the sensor module are installed inside the bioreactor. The light source module includes several red LED units and several blue LED units. The light intensity and spectrum of the red LED units and blue LED units can be modulated by the control center. The sensor is signal-connected to the control center and includes a photometric sensor.

[0046] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0047] I. Preparation Method Example 1 A system for improving the oil yield of bacteria and algae based on diurnal rhythm light regulation includes a 5L flat-plate photobioreactor. Several red LED units and several blue LED units with modulated light intensity and spectrum are arranged on both sides of the reactor. The red LED units and blue LED units are connected to the control center, which can modulate their light intensity and spectrum. The reactor is equipped with a pH monitor, a DO monitor and a photometric sensor, all of which are connected to the PLC control center.

[0048] Example 2 A method for improving the oil yield of bacteria and algae based on diurnal light regulation includes the following steps: Phase A: Chlorella vulgaris in its logarithmic growth phase was inoculated into BG-11 medium at an initial OD680 of 0.5 (approximately 0.25 g / L dry weight) and placed in the photobioreactor described in Example 1. The control center executed the first illumination program, with a light-to-dark ratio of 16:8 and a light intensity of 400 μmol / m². 2 / s, the ratio of red light intensity to red-blue light intensity in the spectrum is 7:1; the temperature during the cultivation of oil-producing microorganisms is 25±1℃, and air containing 2% CO2 is introduced into the culture medium.

[0049] Phase B: After monitoring that the sodium nitrate in the culture medium has been consumed to 10% of its initial concentration, the second illumination program is switched to: the light-to-dark ratio of the illumination cycle is 8:16, and ultra-high intensity pulsed light and medium-low intensity recovery light are used alternately for illumination. The intensity of ultra-high intensity pulsed light is 500 μmol / m2 / s, and the illumination time is 15 min; the intensity of medium-low intensity recovery light is 200 μmol / m2 / s, and the illumination time is 45 min. The intensity ratio of blue-rich light to red-blue light in the spectrum is 2:1.

[0050] Phase C: If the growth rate of oil content in the culture medium is less than 5% within 36 consecutive hours, it is determined to have entered the plateau phase. After the oil content in the culture medium enters the plateau phase, switch to the third light program: the light-to-dark ratio of the light cycle is 6:18, the light intensity is 50 μmol / m2 / s, and the ratio of red-rich light to red-blue light intensity in the spectrum is 7:1 according to the photon flux density. The oil is harvested after 24 hours of cultivation.

[0051] A method for improving the oil yield of bacteria and algae based on diurnal light regulation includes the following steps: Phase A: BG-11 medium inoculated with Scenedesmus was placed in the photobioreactor of Example 1. The control center executed the first illumination program, with a light:dark ratio of 14:10 and a light intensity of 450 μmol / m². 2 / s, the ratio of red light intensity to red-blue light intensity in the spectrum is 6:1; the temperature during the cultivation of oil-producing microorganisms is 25±1℃, and air containing 2% CO2 is introduced into the culture medium.

[0052] Phase B: After monitoring that the sodium nitrate in the culture medium has been consumed to 15% of its initial concentration, the second illumination program is switched to: the light-to-dark ratio of the illumination cycle is 7:17, and ultra-high intensity pulsed light and medium-low intensity recovery light are used alternately for illumination. The intensity of ultra-high intensity pulsed light is 450 μmol / m² / s, and the illumination time is 10 min; the intensity of medium-low intensity recovery light is 150 μmol / m² / s, and the illumination time is 50 min. The intensity ratio of blue-rich light to red-blue light in the spectrum is 1.5:1.

[0053] Phase C: If the growth rate of oil content in the culture medium is less than 5% within 48 consecutive hours, it is determined to have entered the plateau phase. After the oil content in the culture medium enters the plateau phase, switch to the third light program: the light-to-dark ratio of the light cycle is 5:19, the light intensity is 30 μmol / m² / s, and the intensity ratio of red-rich light to red-blue light in the spectrum is 6:1. The oil is harvested after 36 hours of cultivation.

[0054] Example 4 A method for improving the oil yield of bacteria and algae based on diurnal light regulation includes the following steps: Phase A: YPD medium inoculated with Rhodotorula glutinis was placed in the photobioreactor of Example 1. The control center executed the first illumination program, with a light:dark ratio of 18:6 and a light intensity of 350 μmol / m². 2 / s, the ratio of red light intensity to red-blue light intensity in the spectrum is 8:1; the temperature during the cultivation of oil-producing microorganisms is 25±1℃, and air containing 2% CO2 is introduced into the culture medium.

[0055] Phase B: After monitoring that the nitrogen source in the culture medium has been consumed to 5% of its initial concentration, the second illumination program is switched to: the light-to-dark ratio of the illumination cycle is 9:15, and ultra-high intensity pulsed light and medium-low intensity recovery light are used alternately for illumination. The intensity of ultra-high intensity pulsed light is 550 μmol / m² / s, and the illumination time is 5 min; the intensity of medium-low intensity recovery light is 250 μmol / m² / s, and the illumination time is 25 min. The intensity ratio of blue-rich light to red-blue light in the spectrum is 2.5:1.

[0056] Phase C: If the growth rate of oil content in the culture medium is less than 5% within 24 consecutive hours, it is determined to have entered the plateau phase. After the oil content in the culture medium enters the plateau phase, switch to the third light program: the light-to-dark ratio of the light cycle is 7:17, the light intensity is 20 μmol / m² / s, and the ratio of red-rich light to red-blue light intensity in the spectrum is 8:1. The oil is harvested after 48 hours of cultivation.

[0057] Comparative Example 1 A method for improving the yield of bacterial and algal lipids includes the following steps: placing BG-11 medium inoculated with Chlorella in a photobioreactor and using constant illumination at a light intensity of 400 μmol / m². 2 The light intensity was 1 / s, the spectrum was a fixed red-blue light ratio of 1:1, the temperature during cultivation was 25±1℃, and air containing 2% CO2 was introduced into the culture medium. The cultivation time was the same as in Example 2, until the oil was harvested.

[0058] Comparative Example 2 A method for improving the yield of bacterial and algal lipids includes the following steps: placing BG-11 medium inoculated with Chlorella in a photobioreactor, using a simple light-dark cycle with a light:dark ratio of 12:12 and a light intensity of 400 μmol / m². 2 The light intensity was 1 / s, the spectrum was a fixed red-blue light ratio of 1:1, the temperature during cultivation was 25±1℃, and air containing 2% CO2 was introduced into the culture medium. The cultivation time was the same as in Example 2, until the oil was harvested.

[0059] Comparative Example 3 A method for increasing the yield of bacterial and algal oil includes the following steps: the steps are basically the same as in Example 2, but no spectral adjustment is performed at any stage, and a fixed red-blue light ratio of 1:1 is used for illumination throughout the process. All other conditions (timing of photoperiod switching, pulse light intensity, temperature, CO2, etc.) are kept consistent with those in Example 2.

[0060] II. Testing Methods Oil yield determination method: Total lipids were extracted using the chloroform-methanol method (Bligh and Dyer method), and the dry weight of the oil was determined by gravimetric method. The oil yield per unit volume of culture medium (g / L) was then calculated.

[0061] III. Analysis of Test Results for Each Embodiment and Comparative Example The final oil yield of each embodiment and comparative example was tested, and the test results are shown in Table 1 below.

[0062] Table 1 Final oil yield test results

[0063] As shown in Table 1 above, the method for cultivating bacteria and algae based on diurnal light regulation provided by this invention significantly improves the lipid yield for both microalgae and yeast compared to traditional constant light or simple light-dark cycle cultivation methods. This indicates that the technical effects of this invention are stable, reproducible, and significant within the scope of protection.

[0064] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for improving the yield of bacterial and algal oils based on diurnal light regulation, characterized in that, The process includes the following steps: inoculating oil-producing microorganisms into a culture medium, and sequentially inducing the oil-producing microorganisms to produce oil using a first light program, a second light program, and a third light program; The first illumination program has a light-to-dark ratio of (12:12) to (20:4) and a red-rich light to red-blue light intensity ratio of (5:1) to (9:1) in the spectrum. After the concentration of the indicator nutrient factor in the culture medium is consumed to the set threshold, the second illumination program is switched: the light:dark ratio of the illumination cycle is (6:18)~(10:14), and ultra-high intensity pulsed light and medium-low intensity recovery light are used alternately for illumination. The intensity ratio of blue-rich light to red-blue light in the spectrum is (1:1)~(3:1). After the oil content in the culture medium reaches a plateau, the third light program is switched: the light-to-dark ratio of the light cycle is (4:20) to (8:16), the intensity ratio of red-rich light to red-blue light in the spectrum is (5:1) to (9:1), and the oil is harvested after 12 to 48 hours of cultivation.

2. The method for improving bacterial and algal oil yield based on diurnal light regulation according to claim 1, characterized in that, In the second illumination program, the intensity of the ultra-high intensity pulsed light is 200~600 μmol / m². 2 / s, illumination time is 5~30min; The intensity of the low-to-medium intensity recovery light is 100~400 μmol / m 2 / s, with an illumination time of 20~60min.

3. The method for improving bacterial and algal oil yield based on diurnal light regulation according to claim 1, characterized in that, In the first illumination program, the light intensity is 200~600 μmol / m². 2 / s; In the third illumination program, the light intensity is 20~100 μmol / m². 2 / s.

4. The method for improving the yield of bacterial and algal oils based on diurnal light regulation according to claim 1, characterized in that, The temperature during the cultivation of the oil-producing microorganisms is 25±1℃, and air containing 1%~5% CO2 is introduced into the culture medium.

5. The method for improving bacterial and algal oil yield based on diurnal light regulation according to claim 1, characterized in that, Oil-producing microorganisms include microalgae and oil-producing yeasts.

6. The method for improving bacterial and algal oil yield based on diurnal light regulation according to claim 5, characterized in that, The microalgae include at least one of the genera Chlorella, Scenedesmus, and Brown's Finger; and / or The oil-producing yeast includes at least one of Rhodotorula glutinis and Rhodotorula spp.

7. The method for improving bacterial and algal oil yield based on diurnal light regulation according to claim 1, characterized in that, The culture medium includes at least one of BG-11 medium and YPD medium.

8. The method for improving the yield of bacterial and algal oils based on diurnal light regulation according to claim 1, characterized in that, The indicator nutrient factor includes at least one of nitrogen source, phosphorus source and sulfur source, and the set threshold is 5% to 20%.

9. The method for improving bacterial and algal oil yield based on diurnal light regulation according to claim 1, characterized in that, In the second illumination program, if the growth rate of lipid content in the culture medium is less than 5% for 24-48 hours, it is determined to have entered the plateau phase; otherwise, it has not entered the plateau phase.

10. A system for improving the yield of bacterial and algal oils based on diurnal light regulation, characterized in that, A method for improving the yield of bacterial and algal lipids based on diurnal light regulation as described in any one of claims 1 to 9, comprising a photobioreactor, a light source module, a sensor module, and a control center, wherein the culture medium is located within the photobioreactor, the light source module and the sensor module are installed within the bioreactor, the light source module includes a plurality of red LED units and a plurality of blue LED units, the light intensity and spectrum of the red LED units and the blue LED units can be modulated by the control center, the sensor is signal-connected to the control center, and the sensor includes a photometric sensor.

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