Preparation method of betaine-rich yeast extract

Abstract

The present invention relates to the field of biotechnology, and particularly to a preparation method of yeast extract rich in betaine. The present invention provides a preparation method of yeast extract rich in betaine. Among them, the yeast extract rich in betaine includes protein, amino acids, peptides, nucleotides, and betaine. The mass percentage content of protein is 50% - 75%, and the mass percentage content of betaine is 0.2% - 4%. In the present invention, yeast rich in betaine is obtained by the yeast absorbing and enriching betaine in the betaine-rich carbon source during the growth process, and then the yeast extract rich in betaine is obtained through enzymatic hydrolysis and refinement. This technology makes up for the blank of yeast extract of betaine, and is mainly involved in the fields of food, health food, feed, medicine, etc.

Description

Technical Field

[0001] The present invention relates to the field of biotechnology, and particularly to a method for preparing a betaine-rich yeast extract. Background Art

[0002] Betaine is an alkaloid, highly soluble in water, commonly present in animals and plants, is an intermediate product of animal metabolism, plays a very important role in the metabolism of nutrients, and is also a very important osmotic regulatory substance. Naturally sourced betaine is widely used in the food industry. The specific proposed level (SPL) of ingested betaine is 1.5 g / day, which can mainly provide active methyl groups, reduce serum homocysteine levels; save methionine and promote protein synthesis; promote lipid metabolism and inhibit liver lipid deposition; regulate cell osmotic pressure and reduce environmental stress responses.

[0003] Currently, the preparation of betaine mainly includes two methods: extraction method and synthesis method. Among them, the extraction method mainly relies on recovering betaine from beet molasses. Its advantages are that the raw material source is relatively rich, and the extraction process does not require complex chemical reactions, resulting in less environmental pollution. However, the extraction efficiency of this method is greatly affected by the betaine content in the molasses, and other impurities may be introduced during the extraction process, resulting in low product purity. The synthesis method directly prepares betaine through chemical reactions. Its advantages are high product purity, high yield, and not being limited by the betaine content in the raw materials. However, the synthesis method requires the use of chemical reagents, which may cause certain pollution to the environment, and the reaction conditions need to be strictly controlled during the operation process to ensure the quality and safety of the product.

[0004] It can be seen that there are certain drawbacks in the preparation of betaine by either the extraction method or the synthesis method. Yeast extract is a natural product obtained by enzymatically hydrolyzing and refining edible yeast to release proteins and nucleic acids in yeast cells, rich in polypeptides, amino acids, and nucleotides, providing rich nutrients. As a food ingredient, its natural and rich nutritional components make it widely used in the food processing industry. The betaine yeast extract has better physiological effects through synergistic effects, but there is currently no report on betaine yeast extract. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing a betaine-rich yeast extract.

[0006] The present invention provides a method for preparing a betaine-rich yeast extract, including: fermenting and culturing yeast, and then obtaining an extract through enzymatic hydrolysis.

[0007] In the present invention, betaine-rich yeast is obtained by yeast absorbing and enriching betaine in a betaine-rich carbon source during growth, and then a betaine-rich yeast extract is obtained through enzymatic hydrolysis and refinement; the betaine-rich yeast extract includes protein, amino acids, peptides, nucleotides, and betaine, with the mass percentage of protein being 50% - 75% and the mass percentage of betaine being 0.2% - 4%.

[0008] In the present invention, the yeast in the preparation method is yeast with good enrichment and absorption ability for betaine. In the examples, the yeast is at least one of Saccharomyces cerevisiae, Pichia pastoris, Saccharomyces boulardii, Candida sp., and Saccharomycopsis fibuligera. Compared with other types of yeast, the yeast as described above can enrich a higher content of betaine. For example, the yeast in the present invention can be any one of Saccharomyces cerevisiae, Pichia pastoris, Saccharomyces boulardii, Candida sp., and Saccharomycopsis fibuligera, or it can also be a composite bacterium of at least two of the yeasts as described above. For example, the yeast is Saccharomyces cerevisiae and Pichia pastoris, or Saccharomyces cerevisiae and Saccharomyces boulardii, or Saccharomyces cerevisiae and Candida sp., or Saccharomyces cerevisiae and Saccharomycopsis fibuligera, or Pichia pastoris and Saccharomyces boulardii, or Pichia pastoris and Saccharomyces boulardii, or Pichia pastoris and Saccharomycopsis fibuligera, or Saccharomyces boulardii and Candida sp., or Saccharomyces boulardii and Saccharomycopsis fibuligera, or Saccharomyces cerevisiae, Pichia pastoris and Saccharomyces boulardii, or Saccharomyces cerevisiae, Pichia pastoris and Candida sp., or Saccharomyces cerevisiae, Pichia pastoris and Saccharomycopsis fibuligera, or Saccharomyces cerevisiae, Saccharomyces boulardii and Saccharomycopsis fibuligera, or Saccharomyces cerevisiae, Candida sp. and Saccharomycopsis fibuligera, or Pichia pastoris, Saccharomyces boulardii and Candida sp., or Pichia pastoris, Saccharomyces boulardii and Saccharomycopsis fibuligera, or Saccharomyces boulardii, Candida sp. and Saccharomycopsis fibuligera.

[0009] In specific examples, the Saccharomyces cerevisiae is Saccharomyces cerevisiae strain FX-2 (preservation number: CCTCC NO: M2016418), the Pichia pastoris is Pichia pastoris C1.8 (preservation number: CCTCC NO: M2017780), the Saccharomyces boulardii is Saccharomyces boulardii Angel 1.27 (preservation number: CCTCC NO: M2012116), the Candida sp. is Candida sp. C1.7 (preservation number: CCTCC NO: M2017782), and the Saccharomycopsis fibuligera is Saccharomycopsis fibuligera d6.16 (preservation number: CCTCC NO: M2019570).

[0010] In the present invention, during the yeast growth and fermentation process, a carbon source rich in betaine (2% - 8%) is added, KCl and NaCl are added, and the N source and P source are added in advance and added dropwise to completion so that the yeast can fully absorb and enrich betaine to obtain betaine-rich yeast, and then an enzymatic hydrolysis process is used to break the yeast cell wall to release intracellular substances.

[0011] In the present invention, the culture medium for fermentation culture comprises: beet molasses, ammonia water, NaCl, KCl, NH4H2PO4, copper sulfate, biotin, VB1 and VB2.

[0012] Among them, the beet molasses is a by-product in the beet sugar industry. It is the thick liquid remaining after the beet is pressed and the sugar is extracted during the process of processing the beet into sugar. The content of betaine therein is 2% - 8%. Specifically, in the beet molasses, the content of betaine calculated on a dry basis in terms of reducing sugar is 2% - 8%.

[0013] Among them, the copper sulfate can also be a hydrate of copper sulfate, for example: copper sulfate pentahydrate (CuSO4·5H2O) and / or copper sulfate monohydrate (CuSO4·H2O). The ammonia water is ammonia water with a mass fraction of 20%, calculated based on the content of N.

[0014] The culture medium has an important influence on the active ingredients in the prepared extract. In the culture medium of the present invention, the nutrients are reasonably set, which is more conducive to the enrichment of betaine. Compared with the culture medium without potassium ions, sodium ions or with inappropriate ratios and concentrations, the culture medium of the present invention is used for the cultivation of yeast, and the content of betaine in the obtained yeast extract is higher.

[0015] In some embodiments, the culture medium comprises water and 80 - 200 g / L of beet molasses, 5 - 30 mL / L of 20% ammonia water, 2 - 20 g / L of NaCl, 2 - 20 g / L of KCl, 1 - 5 g / L of NH4H2PO4, 0.001 - 0.05 g / L of copper sulfate pentahydrate, 0.001 - 0.05 g / L of biotin, 0.002 - 0.2 g / L of VB1 and 0.001 - 0.1 g / L of VB2.

[0016] More specifically, the culture medium consists of water and the following components: 150 g / L of beet molasses (the content of betaine calculated on a dry basis in terms of reducing sugar is 4%), 30 mL / L of ammonia water with a mass concentration of 20%, 6 g / L of NaCl, 2 g / L of KCl, 3 g / L of NH4H2PO4, 0.005 g / L of copper sulfate pentahydrate, 0.02 g / L of biotin, 0.01 g / L of VB1, and 0.002 g / L of VB2.

[0017] After fermentation in the present invention, betaine is better dissolved by enzymatic hydrolysis. In the present invention, the enzymes for enzymatic hydrolysis include at least one of protease, mannanase and / or β-glucanase. For example, the enzymatic hydrolysis uses protease, or mannanase, or β-glucanase, or protease and mannanase, or protease and β-glucanase, or mannanase and β-glucanase, or protease, mannanase and β-glucanase.

[0018] In some embodiments, in the enzymatic hydrolysis step, the mass of the enzyme is 0.1% to 1% of the mass of the yeast, and the conditions for enzymatic hydrolysis include 40 to 70 °C, pH adjusted to 5 to 7, and enzymatic hydrolysis for 5 to 20 h.

[0019] In some specific embodiments, the enzymatic hydrolysis is protease enzymatic hydrolysis. The mass of the enzyme is 0.1% to 1% of the mass of the yeast, and the conditions for enzymatic hydrolysis include 40 to 60 °C, pH adjusted to 5 to 6, and enzymatic hydrolysis for 15 to 20 h. Preferably, the conditions for protease enzymatic hydrolysis include that the mass of the enzyme is 0.5% of the mass of the yeast, the conditions for enzymatic hydrolysis include 50 °C, pH adjusted to 5.5, and enzymatic hydrolysis for 18 h.

[0020] In some specific embodiments, the enzymatic hydrolysis is mannanase and β-glucanase enzymatic hydrolysis. Among them, the mass ratio of mannanase to β-glucanase is 1:1. The mass of the enzyme is 0.1% to 1% of the mass of the yeast, and the conditions for enzymatic hydrolysis include 50 to 70 °C, pH adjusted to 4.5 to 5.0, and enzymatic hydrolysis for 10 to 20 h. Preferably, the mass of the enzyme is 0.2% of the mass of the yeast, the conditions for enzymatic hydrolysis include 60 °C, pH adjusted to 5.0, and enzymatic hydrolysis for 15 h.

[0021] The present invention optimizes and improves the fermentation conditions. The optimized conditions for the fermentation include: the initial fermentation culture medium does not contain beet molasses, ammonia water or NH4H2PO4, and beet molasses, ammonia water and NH4H2PO4 are added dropwise during the fermentation process.

[0022] In some embodiments, at the beginning of fermentation, the composition of the culture medium is water and 2 to 20 g / L of NaCl, 2 to 20 g / L of KCl, 0.001 to 0.05 g / L of copper sulfate pentahydrate, 0.001 to 0.05 g / L of biotin, 0.002 to 0.2 g / L of VB1 and 0.001 to 0.1 g / L of VB2. A total of 80 to 200 g / L of beet molasses, 5 to 30 mL / L of 20% ammonia water, and 1 to 5 g / L of NH4H2PO4 are added dropwise to each liter of the culture medium.

[0023] More specifically, during the fermentation process, adjust the flow rate of beet molasses so that the mass fraction of ethanol in the fermentation system is not higher than 0.3%; adjust the flow rate of NH4H2PO4 so that the mass fraction of P2O5 in the yeast is 1% to 5%; adjust the flow rate of ammonia water so that the mass fraction of protein in the yeast is 30% to 60%.

[0024] In some specific embodiments, NH4H2PO4 is added dropwise completely at 400 to 500 min during fermentation, and ammonia water is added dropwise completely at 500 to 720 min.

[0025] The fermentation conditions further include: rotation speed of 200 - 700 rpm, sterile air flow rate of 0.5 - 4 L air / (L fermentation broth × min), fermentation temperature of 28 - 35 °C, and fermentation time of 10 - 20 h. Preferably, the rotation speed is 200 - 600 rpm, the sterile air flow rate is 1 - 3 L air / (L fermentation broth × min), the fermentation temperature is 30 °C, and the fermentation time is 15 h.

[0026] In the present invention, in the fermentation step, the yeast concentration in the culture broth after inoculation is 50 g / L.

[0027] In the examples of the present invention, before the fermentation, there are also steps of shake flask seed culture and seed fermentation;

[0028] The medium for the shake flask seed culture includes water, 80 - 120 g / L glucose, 10 - 30 g / L yeast extract, 0.8 - 1.2 g / L KH2PO4, and 0.8 - 1.2 g / L MgSO4; preferably, the shake flask seed medium consists of water and components with the following concentrations: 100 g / L glucose, 20 g / L yeast extract, 1 g / L NH4H2PO4, 1 g / L MgSO4.

[0029] The medium for the seed fermentation includes water, 50 - 150 g / L beet molasses, 0.5 - 2.0 g / L magnesium sulfate, 10 - 30 g / L ammonium sulfate, 1 - 5 g / L NH4H2PO4, 0.004 - 0.02 g / L copper sulfate pentahydrate, 0.001 - 0.5 g / L biotin, 0.002 - 0.2 g / L VB1, and 0.001 - 0.1 g / L VB2. Preferably, the medium for the seed fermentation consists of water and components with the following concentrations: beet molasses (calculated as reducing sugar, betaine content dried and calculated as 6%) 100 g / L, magnesium sulfate 1.0 g / L, ammonium sulfate 30 g / L, NH4H2PO4 3 g / L, copper sulfate pentahydrate 0.005 g / L, biotin 0.02 g / L, VB1 0.01 g / L, and VB2 0.002 g / L.

[0030] In the present invention, before the enzymolysis after the fermentation, there is also a step of high - pressure homogenization for cell wall breaking. The conditions for the high - pressure homogenization for cell wall breaking include: after washing the fermentation product, making it into a suspension with a mass fraction of 10% - 15%, the pressure of high - pressure homogenization is 1000 - 1500 bar, and the feeding speed is 5 - 10 L / h. Preferably, the homogenization includes: after washing the fermentation product, making it into a suspension with a mass fraction of 10%, the pressure of high - pressure homogenization is 1300 bar, and the feeding speed is 8 L / h.

[0031] In the present invention, after the enzymolysis in the preparation method, there are also steps of enzyme inactivation, membrane separation, and / or drying.

[0032] The conditions for enzyme inactivation include treating at 80-100 °C for 0.5-2 h; preferably, the conditions for enzyme inactivation are treating at 90 °C for 1 h.

[0033] The cut-off molecular weight for membrane separation is 20-500 kDa; preferably, the cut-off molecular weight is 500 kDa.

[0034] In some specific embodiments, the preparation method includes:

[0035] The yeast is subjected to shake flask seed culture, seed fermentation, then commercial fermentation, and then enzymolysis is carried out with at least one of protease, mannanase, and β-glucanase to obtain the extract;

[0036] Among them, the yeast is at least one of Saccharomyces cerevisiae, Pichia pastoris, Saccharomyces boulardii, Candida, and Saccharomycopsis fibuligera;

[0037] The medium for shake flask seed culture includes water, 80-120 g / L glucose, 10-30 g / L yeast extract, 0.8-1.2 g / L KH2PO4, and 0.8-1.2 g / L MgSO4;

[0038] The medium for seed fermentation includes water, 50-150 g / L beet molasses, 0.5-2.0 g / L magnesium sulfate, 10-30 g / L ammonium sulfate, 1-5 g / L NH4H2PO4, 0.004-0.02 g / L copper sulfate pentahydrate, 0.001-0.5 g / L biotin, 0.002-0.2 g / L VB1, and 0.001-0.1 g / L VB2;

[0039] The culture solution for commercial fermentation includes water and 80-200 g / L beet molasses, 5-30 mL / L of 20% ammonia water, 2-20 g / L NaCl, 2-20 g / L KCl, 1-5 g / L NH4H2PO4, 0.001-0.05 g / L copper sulfate pentahydrate, 0.001-0.05 g / L biotin, 0.002-0.2 g / L VB1, and 0.001-0.1 g / L VB2.

[0040] Or, in some specific embodiments, the preparation method includes:

[0041] The yeast is subjected to shake flask seed culture, seed fermentation, then commercial fermentation, high-pressure homogenization and cell wall breaking at 1300 bar with a feed flow rate of 8 L / h, then enzymolysis is carried out with at least one of protease, mannanase, and β-glucanase, and then after separation with a 500 kDa molecular weight cut-off, the supernatant is separated to obtain the extract;

[0042] Among them, the yeast is at least one of Saccharomyces cerevisiae, Pichia pastoris, Saccharomyces boulardii, Candida sp., and Saccharomycopsis fibuligera;

[0043] The medium for shake flask seed culture comprises water, 80 - 120 g / L glucose, 10 - 30 g / L yeast extract, 0.8 - 1.2 g / L KH₂PO₄, and 0.8 - 1.2 g / L MgSO₄;

[0044] The medium for seed fermentation comprises water, 50 - 150 g / L beet molasses, 0.5 - 2.0 g / L magnesium sulfate, 10 - 30 g / L ammonium sulfate, 1 - 5 g / L NH₄H₂PO₄, 0.004 - 0.02 g / L copper sulfate pentahydrate, 0.001 - 0.5 g / L biotin, 0.002 - 0.2 g / L VB₁, and 0.001 - 0.1 g / L VB₂;

[0045] The culture solution for commercial fermentation comprises water and 80 - 200 g / L beet molasses, 5 - 30 mL / L 20% ammonia water, 2 - 20 g / L NaCl, 2 - 20 g / L KCl, 1 - 5 g / L NH₄H₂PO₄, 0.001 - 0.05 g / L copper sulfate pentahydrate, 0.001 - 0.05 g / L biotin, 0.002 - 0.2 g / L VB₁, and 0.001 - 0.1 g / L VB₂.

[0046] Furthermore, the present invention also provides a betaine-rich yeast extract prepared by the preparation method as described above.

[0047] In the present invention, the mass percentage content of protein in the betaine-rich yeast extract is 50% - 75%, and the mass percentage content of betaine is 0.2% - 4%. In some embodiments, the mass percentage content of protein in the betaine-rich yeast extract is 55.39% - 73.21%, and the mass percentage content of betaine is 0.3% - 4%. In some specific embodiments, the mass percentage content of protein in the betaine-rich yeast extract is 68.64%, and the mass percentage content of betaine is 2%. In some specific embodiments, the mass percentage content of protein in the betaine-rich yeast extract is 70.42%, and the mass percentage content of betaine is 3%. In some specific embodiments, the mass percentage content of protein in the betaine-rich yeast extract is 73.21%, and the mass percentage content of betaine is 4%. In some specific embodiments, the mass percentage content of protein in the betaine-rich yeast extract is 55.39%, and the mass percentage content of betaine is 1.0%. In some specific embodiments, the mass percentage content of protein in the betaine-rich yeast extract is 68.49%, and the mass percentage content of betaine is 0.6%. In some specific embodiments, the mass percentage content of protein in the betaine-rich yeast extract is 69.93%, and the mass percentage content of betaine is 0.3%.

[0048] Furthermore, the present invention also provides a product containing the betaine-rich yeast extract as described above, and the product is a food, a health food, a feed or a drug.

[0049] The present invention provides a preparation method of a betaine-rich yeast extract. Among them, the yeast extract rich in betaine includes protein, amino acids, peptides, nucleotides, and betaine. The mass percentage content of protein is 50% - 75%, and the mass percentage content of betaine is 0.2% - 4%. In the present invention, the yeast rich in betaine is obtained by the yeast absorbing and enriching betaine in the betaine-rich carbon source during the growth process, and then the betaine-rich yeast extract is obtained through enzymatic hydrolysis and refining. This technology makes up for the blank of the betaine yeast extract and mainly relates to the fields of food, health food, feed, medicine, etc. Detailed implementation manners

[0050] The present invention provides a preparation method of a betaine-rich yeast extract. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve it. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all regarded as included in the present invention. The method and application of the present invention have been described through preferred embodiments. Relevant personnel can obviously make changes or appropriate alterations and combinations to the methods and applications in this article without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0051] At present, the preparation process by biosynthesis only involves the preparation and extraction of betaine, and cannot combine the advantages of fermentation strains. The present invention makes up for the blank of yeast extract rich in betaine. The preparation process is simple and pollution-free. Through the absorption and enrichment of betaine-rich carbon sources by yeast during growth, a yeast extract rich in betaine is obtained after enzymatic hydrolysis and refinement. The protein content is 50%-75% by mass, and the betaine content is 0.2%-4% by mass. Betaine and yeast extract play a better physiological role together, increasing the advantages in product application.

[0052] The method for preparing the yeast extract rich in betaine according to the present invention comprises the following steps:

[0053] (1) Shake flask seed culture: Add 100 g of glucose, 20 g of yeast extract, 1 g of KH2PO4, and 1 g of MgSO4 to a 2 L conical flask, add purified water to make up to 1 L, adjust the pH to 5.0, and sterilize at 121 °C for 20 min. Inoculate 2 loops of yeast strain with an inoculation needle and culture at 30 °C and 200 rpm for 24 h to obtain the seed liquid; the yeast includes but is not limited to any one or more of Saccharomyces cerevisiae, Pichia pastoris, Saccharomyces boulardii, Candida spp., and Saccharomycopsis fibuligera.

[0054] (2) Seed fermentation: Inoculate 1 L of the shake flask seed liquid into a seed fermentation tank for continuous fermentation culture. The specific composition of the culture solution in the seed fermentation tank is as follows: beet molasses (calculated as reducing sugar, the content of betaine in terms of dry matter is 2%-8%) 50-150 g / L, magnesium sulfate 0.5-2.0 g / L, ammonium sulfate 10-30 g / L, NH4H2PO4 1-5 g / L, copper sulfate pentahydrate 0.004-0.02 g / L, biotin 0.001-0.5 g / L, VB1 0.002-0.2 g / L, VB2 0.001-0.1 g / L. Among them, the feeding methods of beet molasses, ammonium sulfate, and NH4H2PO4 are feeding. The fermentation conditions are as follows: rotation speed 200-700 rpm, the air volume of sterile air is controlled at 0.5-4 L air / (L fermentation broth × min), the fermentation temperature is 26 °C-35 °C, and the fermentation time is 24 h. After fermentation, the seed fermentation broth is centrifuged by a centrifuge until the yeast concentration is greater than 500 g / L.

[0055] (3) Commercial fermentation: The seed culture solution in the fermenter is added to the commercial fermenter for commercial fermentation. After inoculation, the yeast concentration in the culture solution is 40 - 70 g / L. The specific composition of the culture solution in the commercial fermenter is as follows: beet molasses (calculated as reducing sugar, betaine content dried and calculated as 2 - 8%) 80 - 200 g / L, NaCl 2 - 20 g / L, KCl 2 - 20 g / L, 20% ammonia water by mass concentration 5 - 30 mL / L, NH4H2PO4 1 - 5 g / L, copper sulfate pentahydrate 0.001 - 0.05 g / L, biotin 0.001 - 0.05 g / L, VB1 0.002 - 0.2 g / L, VB2 0.001 - 0.1 g / L. Among them, the feeding methods of beet molasses, ammonia water and NH4H2PO4 are feeding in a flow manner. The culture conditions are: rotation speed 200 - 700 rpm, the air volume of sterile air is controlled at 0.5 - 4 L of air ( / L of fermentation broth × min), the fermentation temperature is 28°C - 35°C, and the fermentation time is 15 h.

[0056] (4) Enzymolysis: The commercial fermentation broth is separated and washed once by a centrifuge to obtain commercial yeast cream. The yeast cream is formulated into a suspension with a mass percentage of 10% - 15%, the temperature is adjusted to 40°C - 70°C, the pH is adjusted to 5.0 - 7.0, and mannanase, β-glucanase or protease with a mass percentage of 0.1% - 1% of the yeast is added, and the reaction is carried out for 5 - 20 h. Then it is heated to 90°C - 100°C for 1 - 2 h, and the supernatant is collected by centrifugal separation to obtain yeast extract. The enzyme preparation is one or a combination of two or more enzymes.

[0057] (5) Preferably, before enzymolysis, it includes but is not limited to high-pressure homogenization and cell wall breaking of the yeast cream: The yeast cream is formulated into a suspension with a mass percentage of 10% - 15%, and through a high-pressure homogenizer, the pressure is set at 1000 - 1500 bar, and the feeding speed is 5 - 10 L / h to obtain cell wall broken yeast cream.

[0058] (6) Drying: The above supernatant is filtered to obtain the permeate, and the permeate is dried to obtain betaine yeast extract (betaine dried and calculated as 0.2% - 4%).

[0059] (7) Preferably, before drying, it includes but is not limited to membrane separation of the supernatant: The above supernatant is formulated into an aqueous solution with a mass percentage of dry matter of 2% - 20%, and then separated by an ultrafiltration membrane with a cut-off molecular weight of 20 - 500 KD, and the permeate is collected.

[0060] The test materials used in the present invention are all ordinary commercially available products and can be purchased in the market. Among them:

[0061] Saccharomyces cerevisiae FX-2 was deposited at the China Center for Type Culture Collection (CCTCC) on August 1, 2016, with the deposit number CCTCC NO: M2016418.

[0062] The protease is an alkaline protease with an enzyme activity of 1000 U / g, and it is from Amano Japan.

[0063] The mannanase is from Novozymes, with an enzyme activity of 100 FBG / g.

[0064] The β-glucanase is from Nagase Japan, with an enzyme activity of 400 U / mL.

[0065] The beet molasses is from COFCO Sugar Co., Ltd., and its preparation method mainly includes juice extraction, purification, filtration, evaporation, and molasses separation.

[0066] The present invention will be further described below in conjunction with the embodiments:

[0067] Example 1 (Protease Enzymolysis)

[0068] This example provides a method for preparing betaine yeast extract, which includes the following steps:

[0069] (1) Shake flask seed culture: Add 100 g of glucose, 20 g of yeast extract, 1 g of KH2PO4, and 1 g of MgSO4 into a 2 L conical flask, add purified water to make up to 1 L, adjust the pH to 5.0, and sterilize at 121 °C for 20 min. Inoculate two loops of Saccharomyces cerevisiae strain FX-2 (deposit number CCTCC NO: M2016418) with an inoculation needle and culture at 30 °C and 200 rpm for 24 h to obtain the seed solution;

[0070] (2) Seed fermentation: Inoculate 1 L of the shake flask seed solution into a seed fermentation tank for continuous fermentation culture. The specific composition of the seed fermentation tank culture solution is: 100 g / L of beet molasses (calculated as reducing sugar, and the betaine content is calculated as dry matter at 4%), 1.0 g / L of magnesium sulfate, 20 g / L of ammonium sulfate, 3 g / L of NH4H2PO4, 0.005 g / L of copper sulfate pentahydrate, 0.02 g / L of biotin, 0.01 g / L of VB1, and 0.002 g / L of VB2. Among them, the feeding methods of beet molasses, ammonium sulfate, and NH4H2PO4 are feeding. The fermentation conditions are: rotation speed 200 - 700 rpm, the sterile air flow rate is controlled at 0.5 - 3 L air / (L fermentation broth × min), the fermentation temperature is 30 °C, and the fermentation time is 24 h. After fermentation, the seed fermentation broth is centrifuged with a centrifuge until the yeast concentration is greater than or equal to 500 g / L.

[0071] (3) Commercial fermentation: Add the seed culture solution in the fermenter into the commercial fermentation tube for commercial fermentation. After inoculation, the yeast concentration in the culture solution is 50 g / L. The specific composition of the culture solution in the commercial fermenter is as follows: beet molasses (calculated as reducing sugar, 4% of betaine content after drying), 150 g / L; ammonia water with a mass concentration of 20%, 30 mL / L; NaCl, 6 g / L; KCl, 2 g / L; NH4H2PO4, 3 g / L; copper sulfate pentahydrate, 0.005 g / L; biotin, 0.02 g / L; VB1, 0.01 g / L; VB2, 0.002 g / L. Among them, the feeding methods of beet molasses, ammonia water and NH4H2PO4 are feeding in a flow manner. NH4H2PO4 is added completely at the 480th minute of fermentation, and ammonia water is added completely at the 600th minute. During the fermentation process, the alcohol content is controlled to be less than or equal to 0.3%, and the feeding rate of beet molasses is adjusted according to the alcohol content.

[0072] The culture conditions are as follows: rotation speed, 200 - 700 rpm; the air volume of sterile air is controlled at 1 - 3 L air / (L fermentation broth * min); fermentation temperature is 30 °C; fermentation time is 15 h.

[0073] (4) Enzymolysis: Separate and wash the commercial fermentation broth once with a centrifuge to obtain commercial yeast cream. Prepare the yeast cream into a suspension with a mass percentage of 10%, adjust the temperature to 50 °C, pH to 5.5, add protease with a percentage of 0.5% of the yeast mass, react for 18 h, heat to 90 °C and treat for 1 h, and centrifuge to separate and collect the supernatant to obtain yeast extract.

[0074] (5) Drying: Filter the above-mentioned supernatant to obtain the permeate, and obtain betaine yeast extract (2% of betaine after drying) after drying the permeate.

[0075] Example 2 (enzymolysis with mannanase and β-glucanase)

[0076] This example provides a method for preparing betaine yeast extract, which includes the following steps:

[0077] (1) Shake flask seed culture: Add 100 g of glucose, 20 g of yeast extract, 1 g of KH2PO4, and 1 g of MgSO4 into a 2 L conical flask, add purified water to make the volume up to 1 L, adjust the pH to 5.0, and sterilize at 121 °C for 20 min. Inoculate two loops of Saccharomyces cerevisiae strain FX-2 with an inoculation needle and culture at 30 °C and 200 rpm for 24 h to obtain the seed solution;

[0078] (2) Seed fermentation: Inoculate 1 L of shake flask seed liquid into a seed fermenter for continued fermentation culture. The specific composition of the seed fermenter culture medium is as follows: beet molasses (calculated as reducing sugar, betaine content dried 6%) 100 g / L, magnesium sulfate 1.0 g / L, ammonium sulfate 30 g / L, NH4H2PO4 3 g / L, copper sulfate pentahydrate 0.005 g / L, biotin 0.02 g / L, VB1 0.01 g / L, VB2 0.002 g / L. Among them, the feeding methods of beet molasses, ammonium sulfate, and NH4H2PO4 are feeding. The fermentation conditions are: rotation speed 200 - 700 rpm, sterile air flow rate controlled at 0.5 - 3 L air / (L fermentation broth * min), fermentation temperature 30 °C, fermentation time 24 h. After fermentation, the seed fermentation broth is centrifuged by a centrifuge until the yeast concentration is greater than or equal to 500 g / L.

[0079] (3) Commercial fermentation: Add the fermenter seed culture medium into a commercial fermentation tube for commercial fermentation. After inoculation, the yeast concentration in the culture medium is 50 g / L. The specific composition of the commercial fermenter culture medium is as follows: beet molasses (calculated as reducing sugar, betaine content dried 6%) 150 g / L, ammonia water with a mass concentration of 20% 30 mL / L, NaCl 6 g / L, KCl 2 g / L, NH4H2PO4 3 g / L, copper sulfate pentahydrate 0.005 g / L, biotin 0.02 g / L, VB1 0.01 g / L, VB2 0.002 g / L. Among them, the feeding methods of beet molasses, ammonia water, and NH4H2PO4 are feeding. NH4H2PO4 is added completely at the 480th minute of fermentation, and ammonia water is added completely at the 600th minute. During the fermentation process, the alcohol content is controlled to be less than or equal to 0.3%, and the feeding rate of beet molasses is adjusted according to the alcohol content. The culture conditions are: rotation speed 600 rpm, sterile air flow rate controlled at 1 - 3 L air / (L fermentation broth * min), fermentation temperature 30 °C, fermentation time 15 h.

[0080] (4) Enzymolysis: Separate and wash the commercial fermentation broth once with a centrifuge to obtain commercial yeast milk. Prepare the yeast milk into a suspension with a mass percentage of 15%, adjust the temperature to 60 °C, pH to 5.0, add mannanase and β-glucanase at 0.2% of the yeast mass percentage, react for 15 h, heat to 90 °C for 1 h, and centrifuge to separate and collect the supernatant to obtain yeast extract.

[0081] (5) Drying: Filter the above-mentioned supernatant to obtain the permeate, and dry the permeate to obtain betaine yeast extract (betaine dried 3%).

[0082] Example 3 (High-pressure homogenization for cell wall breaking + Enzymolysis + Membrane filtration)

[0083] (1)Flask seed culture: Add 100 g of glucose, 20 g of yeast extract, 1 g of KH2PO4, and 1 g of MgSO4 into a 2 L conical flask, make up the volume to 1 L with purified water, adjust the pH to 5.0, and sterilize at 121 °C for 20 min. Inoculate two loops of Saccharomyces cerevisiae strain FX-2 with an inoculation needle and culture at 30 °C and 200 rpm for 24 h to obtain the seed liquid;

[0084] (2)Seed fermentation: Inoculate 1 L of the flask seed liquid into a seed fermentation tank for continuous fermentation culture. The specific composition of the culture medium in the seed fermentation tank is as follows: beet molasses (calculated as reducing sugar, 8% of betaine content on a dry basis) 100 g / L, magnesium sulfate 1.0 g / L, ammonium sulfate 30 g / L, NH4H2PO4 3 g / L, copper sulfate pentahydrate 0.005 g / L, biotin 0.02 g / L, VB1 0.01 g / L, VB2 0.002 g / L. Among them, the feeding methods of beet molasses, ammonium sulfate, and NH4H2PO4 are fed-batch. The fermentation conditions are: rotation speed 200 - 700 rpm, sterile air flow rate controlled at 0.5 - 3 L air / (L fermentation broth × min), fermentation temperature 30 °C, and fermentation time 24 h. After fermentation, the seed fermentation broth is centrifuged by a centrifuge until the yeast concentration is greater than or equal to 500 g / L.

[0085] (3)Commercial fermentation: Add the fermentation tank seed culture medium into a commercial fermentation tube for commercial fermentation. After inoculation, the yeast concentration in the culture medium is 50 g / L. The specific composition of the culture medium in the commercial fermentation tank is as follows: beet molasses (calculated as reducing sugar, 8% of betaine content on a dry basis) 150 g / L, 20% ammonia water 30 mL / L, NaCl 6 g / L, KCl 2 g / L, NH4H2PO4 3 g / L, copper sulfate pentahydrate 0.005 g / L, biotin 0.02 g / L, VB1 0.01 g / L, VB2 0.002 g / L. Among them, the feeding methods of beet molasses, ammonia water, and NH4H2PO4 are fed-batch. NH4H2PO4 is added completely at the 480th minute of fermentation, and ammonia water is added completely at the 600th minute. During the fermentation process, control the alcohol content to be less than or equal to 0.3%, and adjust the feeding rate of beet molasses according to the alcohol content. The culture conditions are: rotation speed 200 - 600 rpm, sterile air flow rate controlled at 1 - 3 L air / (L fermentation broth * min), fermentation temperature 30 °C, and fermentation time 15 h.

[0086] (4)High-pressure homogenization for cell wall breaking: Separate and wash the commercial fermentation broth once with a centrifuge to obtain commercial yeast milk. Prepare the above yeast milk into a suspension with a mass percentage of 10%, and through a high-pressure homogenizer, set the pressure to 1300 bar and the feeding speed to 8 L / h to obtain cell wall-broken yeast milk.

[0087] (5) Enzymatic hydrolysis: For the above-mentioned broken-wall fermented breast milk, adjust the temperature to 50 °C and the pH to 5.5, add protease at 0.5% of the yeast mass percentage, react for 18 h, heat to 90 °C and treat for 1 h, and centrifuge to separate and collect the supernatant to obtain yeast extract.

[0088] (6) Membrane separation: Prepare the above-mentioned yeast extract into an aqueous solution with a dry matter mass percentage of 10%, and then separate it using an ultrafiltration membrane with a cut-off molecular weight of 500 KD, and collect the permeate.

[0089] (7) Drying: Dry the permeate to obtain betaine yeast extract (betaine is 4% based on dry matter).

[0090] Example 4

[0091] This example provides a method for preparing betaine yeast extract, including the following steps:

[0092] The difference from Example 1 is that Saccharomyces cerevisiae FX-2 is replaced with Cyberlindnera fabianii C1.8, which was deposited in the China Center for Type Culture Collection (CCTCC) on December 11, 2017, with the deposit number CCTCC NO: M2017780, deposit address: Wuhan University, Wuhan, China, postal code: 430072; phone number (027)-68754052.

[0093] Example 5

[0094] This example provides a method for preparing betaine yeast extract, including the following steps:

[0095] The difference from Example 1 is that Saccharomyces cerevisiae FX-2 is replaced with Saccharomyces boulardii Angel 1.27, which was deposited in the China Center for Type Culture Collection (CCTCC) on April 16, 2012, with the deposit number CCTCC NO: M2012116, deposit address: Wuhan University, Wuhan, China, postal code: 430072; phone number (027)-68754052.

[0096] Example 6

[0097] This example provides a method for preparing betaine yeast extract, including the following steps:

[0098] The difference from Example 1 is that Saccharomyces cerevisiae FX-2 is replaced by Wickerhamomyces anomalus C1.7, which was deposited at the China Center for Type Culture Collection (CCTCC) on December 11, 2017, with the deposit number CCTCC NO: M2017782, the deposit address: Wuhan University, Wuhan, China, postal code: 430072; telephone (027)-68754052.

[0099] Comparative Example 1 (carbon source is cane molasses or hydrolyzed sugar)

[0100] This example provides a method for preparing betaine yeast extract, which includes the following steps:

[0101] The difference from Example 1 is that the carbon source for seed fermentation and commercial fermentation is cane molasses or hydrolyzed sugar, and the remaining steps are the same.

[0102] Comparative Example 2 (the strain is baker's yeast)

[0103] This example provides a method for preparing betaine yeast extract, which includes the following steps:

[0104] The difference from Example 1 is that the strain for shake flask seed culture is baker's yeast, and the remaining steps are the same.

[0105] Comparative Example 3 (no KCl and NaCl are added in commercial fermentation)

[0106] This example provides a method for preparing betaine yeast extract, which includes the following steps:

[0107] (1) Shake flask seed culture: Add 100 g of glucose, 20 g of yeast extract, 1 g of KH2PO4, and 1 g of MgSO4 into a 2 L conical flask, add purified water to make up to 1 L, adjust the pH to 5.0, and sterilize at 121 °C for 20 min. Inoculate two loops of Saccharomyces cerevisiae strain FX-2 with an inoculation needle and culture at 30 °C and 200 rpm for 24 h to obtain the seed liquid;

[0108] (2)Seed fermentation: Inoculate 1 L of shake flask seed liquid into a seed fermenter for continuous fermentation culture. The specific composition of the seed fermenter culture medium is as follows: beet molasses (calculated as reducing sugar, betaine content calculated as dry matter 4%) 100 g / L, magnesium sulfate 1.0 g / L, ammonium sulfate 30 g / L, NH4H2PO4 3 g / L, copper sulfate pentahydrate 0.005 g / L, biotin 0.02 g / L, VB1 0.01 g / L, VB2 0.002 g / L. Among them, the feeding methods of beet molasses, ammonium sulfate, and NH4H2PO4 are fed-batch. The fermentation conditions are: rotation speed 200 - 700 rpm, sterile air flow rate controlled at 0.5 - 3 L air / (L fermentation broth × min), fermentation temperature 30 °C, fermentation time 24 h. After fermentation, the seed fermentation broth is centrifuged using a centrifuge until the yeast concentration is greater than or equal to 500 g / L.

[0109] (3)Commercial fermentation: Add the seed culture medium in the fermenter into a commercial fermentation tube for commercial fermentation. After inoculation, the yeast concentration in the culture medium is 50 g / L. The specific composition of the commercial fermenter culture medium is as follows: beet molasses (calculated as reducing sugar, betaine content calculated as dry matter 4%) 150 g / L, ammonia water with a mass concentration of 20% 30 mL / L, NH4H2PO4 3 g / L, copper sulfate pentahydrate 0.02 g / L, biotin 0.02 g / L, VB1 0.01 g / L, VB2 0.002 g / L. Among them, the feeding methods of beet molasses, ammonia water, and NH4H2PO4 are fed-batch. NH4H2PO4 is added completely at the 480th minute of fermentation, and ammonia water is added completely at the 600th minute. During the fermentation process, the alcohol content is controlled to be less than or equal to 0.3%, and the feeding rate of beet molasses is adjusted according to the alcohol content. The culture conditions are: rotation speed 200 - 600 rpm, sterile air flow rate controlled at 1 - 3 L air / (L fermentation broth × min), fermentation temperature 30 °C, fermentation time 15 h.

[0110] (4)Enzymolysis: Separate and wash the commercial fermentation broth once using a centrifuge to obtain commercial yeast cream. Prepare the yeast cream into a suspension with a mass percentage of 10%, adjust the temperature to 50 °C, pH to 5.5, add protease at 0.5% of the yeast mass percentage, react for 18 h, heat to 90 °C for 1 h, and centrifuge to separate and collect the supernatant to obtain yeast extract.

[0111] (5)Drying: Dry the permeate to obtain betaine yeast extract (betaine calculated as dry matter 0.05%).

[0112] Comparative Example 4 (N and P sources are added completely at the 840th minute of fermentation)

[0113] This example provides a method for preparing betaine yeast extract, including the following steps:

[0114] (1) Shake flask seed culture: Add 100 g of glucose, 20 g of yeast extract, 1 g of KH2PO4, and 1 g of MgSO4 into a 2 L conical flask, make up the volume to 1 L with purified water, adjust the pH to 5.0, and sterilize at 121 °C for 20 min. Inoculate two loops of Saccharomyces cerevisiae strain FX-2 with an inoculation needle and culture at 30 °C and 200 rpm for 24 h to obtain the seed liquid;

[0115] (2) Seed fermentation: Inoculate 1 L of the shake flask seed liquid into a seed fermentation tank for continuous fermentation culture. The specific composition of the culture medium in the seed fermentation tank is as follows: beet molasses (calculated as reducing sugar, and the betaine content is calculated as dry matter at 4%) 100 g / L, magnesium sulfate 1.0 g / L, ammonium sulfate 30 g / L, NaCl 6 g / L, KCl 2 g / L, NH4H2PO4 3 g / L, copper sulfate pentahydrate 0.02 g / L, biotin 0.02 g / L, VB1 0.01 g / L, VB2 0.002 g / L. Among them, the feeding methods of beet molasses, ammonium sulfate, and NH4H2PO4 are fed-batch. The fermentation conditions are: rotation speed 200 - 700 rpm, the air volume of sterile air is controlled at 0.5 - 3 L air / (L fermentation broth × min), the fermentation temperature is 30 °C, and the fermentation time is 24 h. After fermentation, the seed fermentation broth is centrifuged with a centrifuge until the yeast concentration is greater than or equal to 500 g / L.

[0116] (3) Commercial fermentation: Add the fermentation tank seed culture medium into a commercial fermentation tube for commercial fermentation. After inoculation, the yeast concentration in the culture medium is 50 g / L. The specific composition of the culture medium in the commercial fermentation tank is as follows: beet molasses (calculated as reducing sugar, and the betaine content is calculated as dry matter at 4%) 150 g / L, ammonia water with a mass concentration of 20% 30 mL / L, NaCl 6 g / L, KCl 2 g / L, NH4H2PO4 3 g / L, copper sulfate pentahydrate 0.005 g / L, biotin 0.02 g / L, VB1 0.01 g / L, VB2 0.002 g / L. Among them, the feeding methods of beet molasses, ammonia water, and NH4H2PO4 are fed-batch, and ammonia water and NH4H2PO4 are added completely at the 840th minute of fermentation. The alcohol content during the fermentation process is controlled to be less than or equal to 0.3%, and the feeding rate of beet molasses is adjusted according to the alcohol content. The culture conditions are: rotation speed 200 - 600 rpm, the air volume of sterile air is controlled at 1 - 3 L air / (L fermentation broth × min), the fermentation temperature is 30 °C, and the fermentation time is 15 h.

[0117] (4) Enzymolysis: Separate and wash the commercial fermentation broth once with a centrifuge to obtain commercial yeast cream. Prepare the yeast cream into a suspension with a mass percentage of 10%, adjust the temperature to 50 °C, pH to 5.5, add protease at 0.5% of the yeast mass percentage, react for 18 h, heat to 90 °C for 1 h, and centrifuge to separate and collect the supernatant to obtain yeast extract.

[0118] (5) Drying: The permeate is dried to obtain betaine yeast extract (betaine 0.06% on dry basis).

[0119] Comparative Example 5 (without enzymatic refining)

[0120] This example provides a method for preparing betaine yeast extract, which includes the following steps:

[0121] (1) Shake flask seed culture: Add 100 g of glucose, 20 g of yeast extract, 1 g of KH2PO4, and 1 g of MgSO4 into a 2 L conical flask, make up the volume to 1 L with purified water, adjust the pH to 5.0, and sterilize at 121 °C for 20 min. Inoculate two loops of Saccharomyces cerevisiae strain FX-2 with an inoculation needle and culture at 30 °C and 200 rpm for 24 h to obtain the seed solution;

[0122] (2) Seed fermentation: Inoculate 1 L of the shake flask seed solution into a seed fermentation tank for continuous fermentation culture. The specific composition of the culture solution in the seed fermentation tank is as follows: 100 g / L of beet molasses (calculated based on reducing sugar, betaine content 2% on dry basis), 1.0 g / L of magnesium sulfate, 30 g / L of ammonium sulfate, 3 g / L of NH4H2PO4, 0.005 g / L of copper sulfate pentahydrate, 0.02 g / L of biotin, 0.01 g / L of VB1, and 0.002 g / L of VB2. Among them, the feeding methods of beet molasses, ammonium sulfate, and NH4H2PO4 are feeding in a flow manner. The fermentation conditions are: rotation speed 200 - 700 rpm, sterile air flow rate controlled at 0.5 - 3 L of air / (L of fermentation broth × min), fermentation temperature 30 °C, and fermentation time 24 h. After fermentation, the seed fermentation broth is centrifuged by a centrifuge until the yeast concentration is greater than or equal to 500 g / L.

[0123] (3) Commercial fermentation: Add the fermentation tank seed culture solution into a commercial fermentation tube for commercial fermentation. The yeast concentration in the culture solution after inoculation is 50 g / L. The specific composition of the culture solution in the commercial fermentation tank is as follows: 150 g / L of beet molasses (calculated based on reducing sugar, betaine content 4% on dry basis), 30 mL / L of 20% ammonia water by mass concentration, 6 g / L of NaCl, 2 g / L of KCl, 3 g / L of NH4H2PO4, 0.005 g / L of copper sulfate pentahydrate, 0.02 g / L of biotin, 0.01 g / L of VB1, and 0.002 g / L of VB2. Among them, the feeding methods of beet molasses, ammonia water, and NH4H2PO4 are feeding in a flow manner. NH4H2PO4 is added completely at the 480th minute of fermentation, and ammonia water is added completely at the 600th minute. During the fermentation process, the alcohol content is controlled to be less than or equal to 0.3%, and the feeding rate of beet molasses is adjusted according to the alcohol content. The culture conditions are: rotation speed 200 - 600 rpm, sterile air flow rate controlled at 1 - 3 L of air / (L of fermentation broth × min), fermentation temperature 30 °C, and fermentation time 15 h.

[0124] (4)Drying: The commercial fermentation broth was separated by a centrifuge and washed once to obtain commercial yeast milk. The above yeast milk was formulated into a suspension with a mass percentage of 10%, and after drying, a betaine yeast extract was obtained (betaine calculated on a dry basis is 0.1%%).

[0125] Table 1 Detection results of indicators in the products of examples and comparative examples

[0126]

[0127] Note: The protein content results in each example and each comparative example in the table were statistically analyzed and there was no significant difference (p > 0.05); the betaine content in each example was relatively high. After statistical analysis by SPSS software, the betaine content in each example had a significant difference compared with each comparative example (significant factor p < 0.05).

[0128] The data in Table 1 shows that: compared with each comparative example, the betaine content in the examples is relatively high. The yeast strains provided by the present invention have a strong ability to absorb and enrich betaine in the betaine-rich carbon source during yeast growth. The fermentation process and enzymatic hydrolysis and refining process provided by the present invention can be used to prepare a betaine-rich yeast extract, in which the mass percentage of protein is 50% - 75%, and the mass percentage of betaine is 0.2% - 4%. It can fill the blank in the prior art of lacking betaine-rich yeast extract. Betaine and the yeast extract play a better physiological role together, increasing the advantages of product application.

[0129] The above is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. Preparation method of rich-betaine yeast extract, comprising: After fermenting and culturing yeast, an extract is obtained through enzymatic hydrolysis; The yeast is at least one of Saccharomyces cerevisiae with the preservation number of CCTCC NO: M2016418, Pichia pastoris with the preservation number of CCTCC NO: M2017780, Saccharomyces boulardii with the preservation number of CCTCC NO: M2012116, and Candida sp. with the preservation number of CCTCC NO: M2017782; The culture medium for the fermenting and culturing includes: beet molasses, ammonia water, NaCl, KCl, NH4H2PO4, copper sulfate, biotin, VB1, and VB2; The enzyme for the enzymatic hydrolysis includes at least one of protease, mannanase, and / or β-glucanase; The conditions for the fermentation are: at the beginning of fermentation, the composition of the culture medium is water and 2 - 20 g / L of NaCl, 2 - 20 g / L of KCl, 0.001 - 0.05 g / L of copper sulfate pentahydrate, 0.001 - 0.05 g / L of biotin, 0.002 - 0.2 g / L of VB1, and 0.001 - 0.1 g / L of VB2. During the fermentation process, beet molasses, ammonia water, and NH4H2PO4 are added continuously; Among them, the flow rate of beet molasses is adjusted so that the mass fraction of ethanol in the fermentation system is not higher than 0.3%; the flow rate of NH4H2PO4 is adjusted so that the mass fraction of P2O5 in the yeast is 1% - 5%; the flow rate of ammonia water is adjusted so that the mass fraction of protein in the yeast is 30% - 60%.

2. The preparation method according to claim 1, characterized in that The culture medium includes water and 80 - 200 g / L of beet molasses, 5 - 30 mL / L of 20% ammonia water, 2 - 20 g / L of NaCl, 2 - 20 g / L of KCl, 1 - 5 g / L of NH4H2PO4, 0.001 - 0.05 g / L of copper sulfate pentahydrate, 0.001 - 0.05 g / L of biotin, 0.002 - 0.2 g / L of VB1, and 0.001 - 0.1 g / L of VB2.

3. The preparation method according to claim 1 or 2, characterized in that, The conditions for the fermentation further include: rotation speed of 200 - 700 rpm, sterile air flow rate of 0.5 - 4 L of air / (L of fermentation broth × min), fermentation temperature of 28 - 35 °C, and fermentation time of 10 - 20 h.

4. The preparation method according to claim 1, wherein, In the enzymatic hydrolysis step, the mass of the enzyme is 0.1% - 1% of the mass of the yeast. The conditions for the enzymatic hydrolysis include 40 - 70 °C, pH adjusted to 5 - 7, and enzymatic hydrolysis for 5 - 20 h.

5. The preparation method according to any one of claims 1 to 4, characterized in that, Before the fermentation, there are also steps of shake flask seed culture and seed fermentation; The culture medium for the shake flask seed culture includes water, 80 - 120 g / L of glucose, 10 - 30 g / L of yeast extract, 0.8 - 1.2 g / L of KH2PO4, and 0.8 - 1.2 g / L of MgSO4; The culture medium for seed fermentation comprises water, 50 - 150 g / L of beet molasses, 0.5 - 2.0 g / L of magnesium sulfate, 10 - 30 g / L of ammonium sulfate, 1 - 5 g / L of NH4H2PO4, 0.004 - 0.02 g / L of copper sulfate pentahydrate, 0.001 - 0.5 g / L of biotin, 0.002 - 0.2 g / L of VB1, and 0.001 - 0.1 g / L of VB2.

6. The preparation method according to any one of claims 1 to 4, characterized in that, Before fermentation and after enzymolysis, it further includes a step of high-pressure homogenization for cell wall breaking. The conditions for high-pressure homogenization for cell wall breaking include: after washing the fermentation product, preparing a suspension with a mass fraction of 10% - 15%, with a high-pressure homogenization pressure of 1000 - 1500 bar and a feeding rate of 5 - 10 L / h.

7. The preparation method according to any one of claims 1 to 4, characterized in that, After enzymolysis, it further includes steps of enzyme inactivation, membrane separation, and / or drying. The conditions for enzyme inactivation include treatment at 80 - 100 °C for 0.5 - 2 h. The molecular weight cut-off for membrane separation is 20 - 500 kDa.

8. The betaine-rich yeast extract prepared by any one of claims 1 - 7.

9. The betaine-rich yeast extract according to claim 8, wherein, Wherein the mass percentage content of protein is 50% - 75%, and the mass percentage content of betaine is 0.2% - 4%.

10. A product containing the betaine-rich yeast extract according to claim 8 or 9, and the product is feed.

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