Method for producing carotenoid by enriching halophilic flora by using UASB (Upflow Anaerobic Sludge Blanket) reactor

Abstract

The invention discloses a method for producing carotenoid by enriching halophilic flora by using a UASB (Upflow Anaerobic Sludge Blanket) reactor. The method comprises the following steps: (1) adding NaCl, MgSO4. 7H2O, KCl and FeSO4 into deionized water to prepare an inorganic culture medium; (2) adding a yeast extract, casein amino acid and sodium citrate into the inorganic culture medium in the step (1) to prepare an enrichment culture medium, and performing initial inoculation source enrichment in a shake flask; and (3) preparing a simulated wastewater culture medium, adding the simulated wastewater culture medium into the UASB reactor, inoculating halophilic flora, and enriching to produce carotenoid. The method has the characteristics of low energy consumption, simplicity in regulation and control and low possibility of being polluted by infectious microbes.

Description

Technical Field

[0001] This invention belongs to the field of microbial application technology, specifically relating to a method for producing carotenoids by enriching halophilic bacteria using a UASB reactor. Background Technology

[0002] Carotenoids are a class of natural pigments that have been shown to play important roles in organisms, such as mitigating oxidative damage and preventing tumors and cardiovascular diseases. However, since most animals (including humans) cannot synthesize carotenoids on their own, they must obtain them from external sources. Compared to traditional chemical synthesis, the method of synthesizing carotenoids using microorganisms has significant advantages such as producing natural products that are safe and non-toxic. In particular, halophilic bacteria, whose ability to tolerate high salinity can effectively avoid contamination by other microorganisms and significantly reduce sterilization costs, represent a highly promising green production process.

[0003] However, existing traditional fermentation technologies have inherent drawbacks such as high energy consumption, severe equipment corrosion, and complex process control, resulting in high production costs and making it difficult to demonstrate their market competitiveness in chemical synthesis.

[0004] For example, in the study (DOI: https: / / doi.org / 10.1186 / s12934-023-02274-0), although the production of phytohexene was optimized, there was a fundamental limitation: the method strictly relied on a single pure strain and expensive synthetic culture medium, resulting in high production costs and difficulty in utilizing complex substrates such as wastewater. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the present invention aims to provide a method for producing carotenoids by enriching halophilic bacteria using a UASB reactor. This method has the characteristics of low energy consumption, simple control, and low susceptibility to contamination by other bacteria.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for producing carotenoids by enriching halophilic bacteria using a UASB reactor includes the following steps; Step (1): Add NaCl, MgSO4·7H2O, KCl and FeSO4 to deionized water to prepare an inorganic culture medium; Step (2): Add yeast extract, casein amino acids and sodium citrate to the inorganic culture medium in step (1) to prepare an enrichment culture and perform initial inoculum enrichment based on shake flasks; Step (3): Prepare simulated wastewater culture medium and add it to the UASB reactor, inoculate halophilic bacteria and enrich them to produce carotenoids.

[0007] The specific steps (1) are as follows: Prepare an inorganic culture medium containing 100-200 g / L NaCl, 10-20 g / L MgSO4·7H2O, 1-2 g / L KCl, and 0.5-1 mg / L FeSO4.

[0008] Step (2) specifically involves: Add 5-15 g / L of yeast extract, 5-10 g / L of casein amino acids and 1-5 g / L of sodium citrate to the inorganic culture medium in step (1) to prepare an enrichment culture medium. Sediment from the salt lake was collected at an inoculation ratio of 10%. The bacterial community in the sediment consisted of 50-60% Halomonas, 10-20% Bacillus subtilis, and the remainder were non-enrichment target bacteria. The halophilic bacteria were enriched and cultured at 37°C. After the OD600 value in the shake flask reached the stationary phase, the bacteria were inoculated into the UASB reactor until the operation was stable. This yielded an orange-red halophilic bacterial community with stable bacterial content, which could tolerate high ammonia nitrogen and efficiently synthesize carotenoids. The abundance of Halomonas (a halophilic species that produces high levels of carotenoids) reached 80%.

[0009] Step (3) specifically involves: A. Take the inorganic culture medium prepared in step (1), add 50-100 mg / L ammonia nitrogen and 750-1500 mg / L acetic acid to the inorganic culture medium, and adjust the pH to about 7 to prepare high-salt organic simulated wastewater; B. Introduce the simulated wastewater from step A into a UASB reactor inoculated with halophilic bacteria to enrich the halophilic bacteria; use a water bath to control the temperature in the reactor at 37°C and monitor the dissolved oxygen and pH in the reactor regularly. C. After the internal circulation of the reactor stabilizes and the monitored OD600 value remains constant, the growth of the halophilic bacteria transitions from the logarithmic growth phase to the stationary phase, and the microbial population density remains stable at a high level. At this point, the UASB reactor is enriched with sufficient halophilic bacteria. The halophilic bacteria utilize acetic acid to synthesize acetyl-CoA, some of which enters the TCA cycle to maintain normal metabolic activities, while some synthesize isoprene pyrophosphate (IPP) via the MVA pathway. Subsequently, under the action of phytoene synthase and phytoene desaturase, lycopene is synthesized. Among them, the core carotenoid synthase in the halophilic bacteria, derived from its genome, undergoes a sequential dehydration and structuring process under the action of multiple enzymes to generate two intermediates: dodehydrated phytoerythrin and monodehydrated phytoerythrin. Finally, through the elongation and stabilization of the conjugated system, phytoerythrin (C50 carotenoid) is synthesized as the final product. Halophilic bacteria can efficiently synthesize various carotenoids while maintaining normal metabolism using added acetic acid and ammonia nitrogen. D. Continuously monitor the removal rates of ammonia nitrogen and acetic acid in the reactor; the reactor operates stably and continuously, with considerable removal rates of ammonia nitrogen and acetic acid, and the process enriches carotenoids and achieves stable levels of carotenoid production. The structure of the upflow anaerobic sludge blanket reactor (UASB reactor) is as follows: The reactor body is an acrylic cylinder 3 with a diameter of 100mm, a height of 25cm, and a working capacity of 1.5L. Three sampling ports are evenly arranged on the top and bottom of the cylinder for easy sampling and testing. A drain outlet is set at the bottom of the cylinder to empty the entire reactor. A water inlet is set at the bottom of the reactor and connected to a rubber hose to a water inlet tank 1. It is connected to the reactor body through a circulating peristaltic pump 2 for water intake. The water outlet at the top of the reactor is connected to a water outlet tank 5 through a circulating peristaltic pump 4 for water discharge. Considering the aerobic characteristics of halophilic bacteria, an aeration port is set at the bottom of the reactor. The aeration port is connected to an air pump 6 for aeration, which provides oxygen and upward force for water flow.

[0010] The beneficial effects of this invention are: 1. The UASB reactor used in this invention can provide a safe and favorable environment for the production of carotenoids using high-salt organic wastewater as raw material; 2. This invention abandons the complex model of traditional fermentation that relies on high-temperature and high-pressure sterilization and strict aseptic operation to control contaminating microorganisms. Instead, it adopts an artificially created high-salt environment as the core of the process. By stabilizing the salinity at 100-200 g / L, we construct a biochemical reactor with absolute selectivity for halophilic bacteria. In this environment, the growth of contaminating microorganisms is effectively inhibited, while the target microorganisms can exclusively occupy the fermentation substrate, efficiently converting it into mycorubrin through a unique metabolic pathway. This method not only significantly reduces equipment investment and energy costs but also, by avoiding competition from contaminating microorganisms, allows the substrate to be used to the maximum extent for the synthesis of the target product. Therefore, the abundance of the target halophilic microorganisms in this invention can reach over 80%, higher than the common level of 20%~50%. 3. This invention demonstrates for the first time the feasibility of synthesizing phytorubrin in a system utilizing acetic acid ammonia nitrogen and high-salt enriched bacterial communities. The carotenoid content in the reactor can reach 1.4 mg / L, confirming that under these specific conditions, the enriched bacterial communities can efficiently convert acetic acid into phytorubrin via the MVA pathway. This invention reveals the effective operation of this synthetic pathway in the unconventional "high-salt" system, providing crucial evidence for subsequent process optimization. Attached Figure Description

[0011] Figure 1 A structural diagram of the UASB reactor in this invention.

[0012] Figure 2 A diagram showing the carotenoid content in the reactor of this invention.

[0013] Figure 3This is a schematic diagram illustrating the removal rates of ammonia nitrogen and acetic acid according to the present invention.

[0014] Explanation of markings in the diagram: 1. Water inlet tank; 2. Circulating peristaltic pump; 3. Acrylic cylindrical body; 4. Circulating peristaltic pump; 5. Water outlet tank; 6. Air pump. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings.

[0016] The structure of the UASB reactor described in this invention is as follows: Figure 1 As shown: The reactor body is a 1.5L capacity organic glass cylinder 3. The lower water inlet of the reactor is connected to the water inlet tank 1 via a rubber hose, and is connected to the reactor body via a circulating peristaltic pump 2. The upper water outlet of the reactor is connected to the water outlet tank 5 via a circulating peristaltic pump 4. Considering the aerobic characteristics of halophilic bacteria, an aeration port is set at the bottom of the reactor and connected to an air pump 6 for aeration.

[0017] The method for producing carotenoids using a UASB reactor in this invention includes the following steps: Step (1): Preparation of basal culture medium Prepare a basic culture medium containing 100-200 g / L NaCl, 10-20 g / L MgSO4·7H2O, 1-2 g / L KCl, and 0.5-1 mg / L FeSO4. This culture medium is beneficial for the subsequent addition of various carbon and nitrogen sources to prepare enrichment culture medium and simulated wastewater culture medium. Step (2): Enrichment of initial inoculum Add 5-15 g / L of yeast extract, 5-10 g / L of casein amino acids and 1-5 g / L of sodium citrate to the inorganic culture medium in step (1) to prepare an enrichment medium. Inoculate the bottom sediment of the collected salt lake at an inoculation ratio of 10%, enrich the halophilic bacteria at 37°C, and monitor the OD600 value in the shake flask regularly until it reaches the stable period. Then continue to inoculate it into the UASB reactor until the operation is stable. This will yield an orange-red halophilic bacterial group with stable bacterial content that can tolerate high ammonia nitrogen and can efficiently synthesize carotenoids. The abundance of Halomonas (a halophilic bacterial species that produces high levels of carotenoids) can reach 80%, which is convenient for subsequent carotenoid production. Step (3) Reaction stage A. Take the inorganic culture medium prepared in step (1), add 50-100 mg / L ammonia nitrogen and 750-1500 mg / L acetic acid to the culture medium, and adjust the pH to about 7 to prepare a high-salt organic simulated wastewater, which is convenient for subsequent simulation of the production of carotenoids from high-salt wastewater. B. Introduce the simulated wastewater from step A into a UASB reactor inoculated with halophilic bacteria to enrich the halophilic bacteria; use a water bath to control the temperature in the reactor at 37°C and regularly monitor the dissolved oxygen and pH in the reactor to observe the growth of the bacteria, which is beneficial to the growth and reproduction of the bacteria and the production of carotenoids. C. After the internal circulation of the reactor stabilizes and the monitored OD600 value remains constant, the growth of halophilic bacteria enters the stationary phase from the logarithmic growth phase, and the microbial population density remains stable at a high level. At this time, sufficient halophilic bacteria are enriched in the UASB reactor. The halophilic bacteria use acetic acid to synthesize acetyl-CoA, part of which enters the TCA cycle to maintain normal metabolic activities, and part of which synthesizes isoprene pyrophosphate (IPP) via the MVA pathway. Then, under the action of phytoene synthase and phytoene desaturase, lycopene is synthesized. Subsequently, under the action of various enzymes, d-dehydrated mycorubin and monodehydrated mycorubin are generated in sequence, and finally mycorubin is synthesized. D. Continuously monitor the removal rates of ammonia nitrogen and acetic acid in the reactor; the reactor operates stably and continuously, with considerable removal rates of ammonia nitrogen and acetic acid, and the process enriches carotenoids and achieves stable levels of carotenoid production.

[0018] like Figure 3 As shown, the removal rates of ammonia nitrogen and acetic acid in the staged reactor can reach over 80%. Furthermore, from... Figure 2 It can be seen that the carotenoid content produced can reach 1.429 mg / L.

[0019] Example 1: Step (1): Preparation of basal culture medium Prepare a basic culture medium containing 100 g / L NaCl, 10 g / L MgSO4·7H2O, 1 g / L KCl, and 0.5 mg / L FeSO4. This culture medium is beneficial for the subsequent addition of various carbon and nitrogen sources to prepare enrichment culture medium and simulated wastewater culture medium. Step (2): Enrichment of initial inoculum Add 5 g / L of yeast extract, 5 g / L of casein amino acids and 1 g / L of sodium citrate to the inorganic culture medium in step (1) to prepare an enrichment medium. Inoculate the bottom sediment of the salt lake at an inoculation ratio of 10%, enrich the halophilic bacteria at 37°C, and monitor the OD600 value in the shake flask regularly until it reaches the stable period. Then continue to inoculate into the UASB reactor until the operation is stable. This will yield an orange-red halophilic bacterial group with stable bacterial content that can tolerate high ammonia nitrogen and can efficiently synthesize carotenoids. Among them, the abundance of Haloxylon ammodendron (a halophilic bacterial species that produces high levels of carotenoids) can reach 80%, which is convenient for subsequent carotenoid production. Step (3) Reaction stage A. Take the inorganic culture medium prepared in step (1), add 50 mg / L ammonia nitrogen and 750 mg / L acetic acid to the culture medium, and adjust the pH to 7 to prepare a high-salt organic simulated wastewater, which is convenient for subsequent simulation of the production of carotenoids from high-salt wastewater; B. Introduce the simulated wastewater from step A into a UASB reactor inoculated with halophilic bacteria to enrich the halophilic bacteria; use a water bath to control the temperature in the reactor at 37°C and regularly monitor the dissolved oxygen and pH in the reactor to observe the growth of the bacteria, which is beneficial to the growth and reproduction of the bacteria and the production of carotenoids. C. After the internal circulation of the reactor stabilizes and the monitored OD600 value remains constant, the growth of halophilic bacteria enters the stationary phase from the logarithmic growth phase, and the microbial population density remains stable at a high level. At this time, sufficient halophilic bacteria are enriched in the UASB reactor. The halophilic bacteria use acetic acid to synthesize acetyl-CoA, part of which enters the TCA cycle to maintain normal metabolic activities, and part of which synthesizes isoprene pyrophosphate (IPP) via the MVA pathway. Then, under the action of phytoene synthase and phytoene desaturase, lycopene is synthesized. Subsequently, under the action of various enzymes, d-dehydrated mycorubin and monodehydrated mycorubin are generated in sequence, and finally mycorubin is synthesized. D. Continuously monitor the removal rates of ammonia nitrogen and acetic acid in the reactor; the reactor operates stably and continuously, with considerable removal rates of ammonia nitrogen and acetic acid, and the process enriches carotenoids and achieves stable levels of carotenoid production.

[0020] Example 2: Step (1): Preparation of basal culture medium Prepare a basic culture medium containing 200 g / L NaCl, 20 g / L MgSO4·7H2O, 2 g / L KCl, and 1 mg / L FeSO4. This culture medium is beneficial for the subsequent addition of various carbon and nitrogen sources to prepare enrichment culture medium and simulated wastewater culture medium. Step (2): Enrichment of initial inoculum Add 15 g / L of yeast extract, 10 g / L of casein amino acids and 5 g / L of sodium citrate to the inorganic culture medium in step (1) to prepare an enrichment medium. Inoculate the bottom sediment of the salt lake at an inoculation ratio of 10%, enrich the halophilic bacteria at 37°C, and monitor the OD600 value in the shake flask regularly until it reaches the stable period. Then continue to inoculate into the UASB reactor until the operation is stable. This will yield an orange-red halophilic bacterial group with stable bacterial content that can tolerate high ammonia nitrogen and can efficiently synthesize carotenoids. Among them, the abundance of Haloxylon ammodendron (a halophilic bacterial species that produces high levels of carotenoids) can reach 80%, which is convenient for subsequent carotenoid production. Step (3) Reaction stage A. Take the inorganic culture medium prepared in step (1), add 100 mg / L ammonia nitrogen and 1500 mg / L acetic acid to the culture medium, and adjust the pH to 7 to prepare a high-salt organic simulated wastewater, which is convenient for subsequent simulation of the production of carotenoids from high-salt wastewater; B. Introduce the simulated wastewater from step A into a UASB reactor inoculated with halophilic bacteria to enrich the halophilic bacteria; use a water bath to control the temperature in the reactor at 37°C and regularly monitor the dissolved oxygen and pH in the reactor to observe the growth of the bacteria, which is beneficial to the growth and reproduction of the bacteria and the production of carotenoids. C. After the internal circulation of the reactor stabilizes and the monitored OD600 value remains constant, the growth of halophilic bacteria enters the stationary phase from the logarithmic growth phase, and the microbial population density remains stable at a high level. At this time, sufficient halophilic bacteria are enriched in the UASB reactor. The halophilic bacteria use acetic acid to synthesize acetyl-CoA, part of which enters the TCA cycle to maintain normal metabolic activities, and part of which synthesizes isoprene pyrophosphate (IPP) via the MVA pathway. Then, under the action of phytoene synthase and phytoene desaturase, lycopene is synthesized. Subsequently, under the action of various enzymes, d-dehydrated mycorubin and monodehydrated mycorubin are generated in sequence, and finally mycorubin is synthesized. D. Continuously monitor the removal rates of ammonia nitrogen and acetic acid in the reactor; the reactor operates stably and continuously, with considerable removal rates of ammonia nitrogen and acetic acid, and the process enriches carotenoids and achieves stable levels of carotenoid production.

[0021] Example 3: Step (1): Preparation of basal culture medium Prepare a basic culture medium containing 150 g / L NaCl, 15 g / L MgSO4·7H2O, 1 g / L KCl, and 1 mg / L FeSO4. This culture medium is beneficial for the subsequent addition of various carbon and nitrogen sources to prepare enrichment culture medium and simulated wastewater culture medium. Step (2): Enrichment of initial inoculum Add 10 g / L of yeast extract, 7 g / L of casein amino acids and 3 g / L of sodium citrate to the inorganic culture medium in step (1) to prepare an enrichment medium. Inoculate the bottom sediment of the salt lake at an inoculation ratio of 10%, enrich the halophilic bacteria at 37°C, and monitor the OD600 value in the shake flask regularly until it reaches the stable period. Then continue to inoculate into the UASB reactor until the operation is stable. This will yield an orange-red halophilic bacterial group with stable bacterial content that can tolerate high ammonia nitrogen and can efficiently synthesize carotenoids. The abundance of Halomonas (a halophilic bacterial species that produces high levels of carotenoids) can reach 80%, which is convenient for subsequent carotenoid production. Step (3) Reaction stage A. Take the inorganic culture medium prepared in step (1), add 75 mg / L ammonia nitrogen and 1000 mg / L acetic acid to the culture medium, and adjust the pH to 7 to prepare a high-salt organic simulated wastewater, which is convenient for subsequent simulation of the production of carotenoids from high-salt wastewater; B. Introduce the simulated wastewater from step A into a UASB reactor inoculated with halophilic bacteria to enrich the halophilic bacteria; use a water bath to control the temperature in the reactor at 37°C and regularly monitor the dissolved oxygen and pH in the reactor to observe the growth of the bacteria, which is beneficial to the growth and reproduction of the bacteria and the production of carotenoids. C. After the internal circulation of the reactor stabilizes and the monitored OD600 value remains constant, the growth of halophilic bacteria enters the stationary phase from the logarithmic growth phase, and the microbial population density remains stable at a high level. At this time, sufficient halophilic bacteria are enriched in the UASB reactor. The halophilic bacteria use acetic acid to synthesize acetyl-CoA, part of which enters the TCA cycle to maintain normal metabolic activities, and part of which synthesizes isoprene pyrophosphate (IPP) via the MVA pathway. Then, under the action of phytoene synthase and phytoene desaturase, lycopene is synthesized. Subsequently, under the action of various enzymes, d-dehydrated mycorubin and monodehydrated mycorubin are generated in sequence, and finally mycorubin is synthesized. D. Continuously monitor the removal rates of ammonia nitrogen and acetic acid in the reactor; the reactor operates stably and continuously, with considerable removal rates of ammonia nitrogen and acetic acid, and the process enriches carotenoids and achieves stable levels of carotenoid production.

[0022] This invention utilizes a UASB reactor to enrich halophilic bacteria for carotenoid production, representing an innovative and promising biotechnology strategy. Traditional stirred fermenter production methods suffer from high energy consumption and susceptibility to contamination by other microorganisms. This invention leverages the upflow hydraulic characteristics of the UASB reactor and injects high-salt simulated wastewater to construct a stable high-salt culture system within the reactor. Through targeted acclimation, it efficiently enriches halophilic bacteria with strong carotenoid synthesis capabilities. These bacteria can efficiently convert organic matter and total nitrogen in the wastewater and accumulate large quantities of high-value carotenoids in a stable environment with low energy consumption (no need for strong aeration or mechanical stirring) and natural high salinity inhibiting other microorganisms. This achieves the resource recovery of high-salt organic wastewater and the green biosynthesis of high-value pigment products, thus achieving the dual goals of environmental remediation and product profitability.

[0023] This invention utilizes a UASB reactor to enrich halophilic bacteria and produce carotenoids, achieving the conversion of carbon and nitrogen pollutants in high-salinity wastewater into high-value products (carotenoids). This process not only efficiently utilizes the carbon and nitrogen sources in the wastewater as raw materials for microbial synthesis and metabolism, but also simultaneously achieves effective removal of organic pollutants through biotransformation within the system. This provides a highly promising technological pathway for the resource-based and high-value treatment of high-salinity wastewater.

[0024] This application utilizes a reactor to efficiently enrich and retain highly active, high-density mixed halophilic bacterial communities, enabling efficient synthesis directly from inexpensive substrates such as acetic acid-containing wastewater. This successfully overcomes the stringent requirements of pure bacterial culture for substrate purity and sterilization procedures, achieving a creative transformation from the traditional "pure bacteria-feed" paradigm to a new "microbial community-waste" resource utilization paradigm.

Claims

1. A method for producing carotenoids by enriching halophilic bacteria using a UASB reactor, characterized in that, Comprising the following steps: Step (1): NaCl, MgSO4·7H2O, KCl and FeSO4 are added to deionized water to prepare an inorganic culture medium; Step (2): yeast extract, casein amino acid and sodium citrate are added to the inorganic culture medium in step (1) to configure an enrichment culture medium for initial inoculum enrichment in a shake flask; Step (3): a simulated wastewater culture medium is configured and added to a UASB reactor, the halophilic bacteria group is inoculated and enriched to produce carotenoids.

2. The method for producing carotenoids by enriching halophilic bacteria using a UASB reactor according to claim 1, wherein, The step (1) is specifically: An inorganic culture medium containing 100-200 g / L NaCl, 10-20 g / L MgSO4·7H2O, 1-2 g / L KCl and 0.5-1 mg / L FeSO4 is configured.

3. The method for producing carotenoids by enriching halophilic bacteria using a UASB reactor according to claim 1, wherein, The step (2) is specifically: 5-15 g / L of yeast extract, 5-10 g / L of casein amino acid and 1-5 g / L of sodium citrate are added to the inorganic culture medium in step (1) to configure an enrichment culture medium.

4. The method for producing carotenoids by enriching halophilic bacteria using a UASB reactor according to claim 3, wherein, The collected sediment of salt lake is inoculated at a ratio of 10%, the bacterial group in the sediment is 50-60% of Halomonas, 10-20% of Oceanospirillium and the rest is miscellaneous bacteria which are not enrichment objects, the halophilic bacteria are enriched at 37℃, after the OD600 value in the shake flask reaches the stable period, the bacteria are inoculated into the UASB reactor until the operation is stable, and thus an orange-red halophilic bacteria group with stable content, high ammonia nitrogen tolerance and high carotenoid synthesis efficiency is obtained.

5. The method for producing carotenoids by enriching halophilic bacteria using a UASB reactor according to claim 4, wherein, The step (3) is specifically: A, the inorganic culture medium prepared in step (1) is taken, 50-100 mg / L of ammonia nitrogen and 750-1500 mg / L of acetic acid are added to the inorganic culture medium, and the pH is adjusted to 7 to configure a high-salt organic simulated wastewater; B, the simulated wastewater in step A is introduced into the UASB reactor inoculated with the halophilic bacteria group to enrich the halophilic bacteria group; the temperature in the reactor is controlled to be 37℃ by using a water bath, and the dissolved oxygen and pH in the reactor are monitored regularly; C, after the circulation in the reactor is stable and the OD600 value is maintained at a constant value, the growth of the halophilic bacteria group enters the stable period from the logarithmic growth period, and the microbial population density is stably maintained at a high level; at this time, the UASB reactor is enriched with sufficient halophilic bacteria group; the halophilic bacteria group synthesizes acetyl coenzyme A by using acetic acid, part of which enters the TCA cycle to maintain normal metabolic activity, and part of which synthesizes isoprene pyrophosphate (IPP) via the MVA pathway, and then synthesizes lycopene by the action of octahydrolycopene synthase and octahydrolycopene desaturase; and then generates bis-dehydrated bacterioruberin and monodehydrated bacterioruberin in turn, and finally synthesizes bacterioruberin; D, the removal rates of ammonia nitrogen and acetic acid in the reactor are continuously monitored; the reactor is continuously and stably operated, the removal rates of ammonia nitrogen and acetic acid are considerable, carotenoids are enriched in the process, and stable level carotenoid production is achieved.

6. The structure of the UASB reactor for realizing the method in any one of claims 1-5 is as follows, characterized in that, The reactor body is a 100mm diameter, 25cm height, 1.5L working capacity organic glass cylinder (3), and 3 sampling ports are uniformly arranged on the cylinder, which is convenient for sampling and determination. A drainage port is arranged at the lower part of the cylinder for emptying the whole reactor. A water inlet is arranged at the lower part of the reactor and connected with a rubber hose to a water inlet tank (1) through a circulating peristaltic pump (2) connected with the reactor body for water inlet. A water outlet at the upper part of the reactor is connected with a water outlet tank (5) through a circulating peristaltic pump (4) for water outlet. Considering the aerobic characteristics of halophilic bacteria, an aeration port is arranged at the bottom of the reactor, and the aeration port is connected with a gas pump (6) for aeration, which provides water flow upward force while providing oxygen.

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