Kluyveromyces marxianus with high β-glucan content and use thereof

Abstract

The present invention belongs to the field of biotechnology, and specifically relates to a Kluyveromyces marxianus with a high β-glucan content and its use. Specifically, the present invention provides a Kluyveromyces marxianus, which is classified and named Kluyveromyces marxianus ( Kluyveromyces marxianus ) CJA0020, and its deposit number is CCTCC No.M 20241673. The Kluyveromyces marxianus strain screened in the present disclosure has a fast growth rate, and the fermentation product of the strain has a higher biomass and β-glucan content, and its β-glucan content can reach 1.23±0.06 g / L; in batch fed fermentation, the biomass can reach 400 g / Kg (wet weight) after 32 hours of cultivation, and the protein content can reach 45%, and it can also be used to produce yeast single-cell protein.

Description

Technical Field

[0001] The invention belongs to the field of biotechnology, and in particular relates to Kluyveromyces marxianus with high beta-glucan content and application thereof. Background Art

[0002] Yeast β-glucan is one of the main components of yeast cell wall, accounting for 30% to 35% of the cell wall components. It is a natural polysaccharide produced by microorganisms. It is a water-insoluble, branched high-molecular polysaccharide polymer composed of glucose as a monosaccharide. The main chain of yeast β-glucan is β-1,3-d-glucan, and the branch chain is β-1,6-d-glucan. The spatial structure mostly exists in the form of a triple helix, and the molecular weight ranges from thousands to millions. Yeast β-glucan is a natural polysaccharide with unique biological activity. For example, β-glucan can promote the production of IgM antibodies in the body and improve the immunity level of animals or humans. In addition, it also has the functions of regulating blood lipids, regulating intestinal flora, moisturizing, wound repair, lowering cholesterol, and anti-tumor. It has broad application prospects in many fields such as food additives, cosmetics, biomedicine, and animal feed. As early as 2006, China approved the use of curdlan with β-1,3-glucan as the main ingredient as a food additive, and approved yeast β-glucan as a new food ingredient in 2010. In 2021, Document No. 5 of the official website of the National Health Commission further included β-1,3 / α-1,3-glucan made by biological fermentation as a new food ingredient.

[0003] Kluyveromyces marxianus ( Kluyeromyces marxianus ) is a biosafety strain on China's "List of Bacteria Applicable to Food", and has also obtained the safety certifications of the EU's QPS (Qualified Presumption of Safety) and the US's GRAS (Generally Recognized As Safe). It has the characteristics of high safety, fast growth, high biomass, broad substrate spectrum, and high dietary fiber content. It is an ideal production cell for high-quality yeast β-glucan.

[0004] In recent years, as the various biological functions of yeast β-glucan have been gradually recognized and accepted, the demand for yeast β-glucan in the fields of food, medicine, cosmetics, etc. has continued to increase. At present, the methods for extracting yeast β-glucan at home and abroad are relatively mature, and a high extraction rate can be obtained from yeast. However, due to the low content of β-glucan in general yeast, it is still difficult to obtain an ideal β-glucan yield in industrial production. Therefore, it is necessary to continue to expand the resources of Kluyveromyces marxianus strains and screen or develop production strains with high β-glucan content. Summary of the invention

[0005] In order to overcome the shortcoming of low yield of yeast β-glucan in industrial production, the purpose of the present application is to provide a new Kluyveromyces marxianus with high biomass and β-glucan content, which can improve the yield of active β-glucan at the strain level and can also be used for the production of yeast single-cell protein.

[0006] In one aspect, the present disclosure provides a Kluyveromyces marxianus, which is classified as Kluyveromyces marxianus ( Kluyveromyces marxianus )CJA0020, its deposit number is CCTCC No. M 20241673.

[0007] The Kluyveromyces marxianus CJA0020 strain described in the present disclosure has been deposited in the China Center for Type Culture Collection (CCTCC for short, address: Wuhan University, Wuhan, China) on July 22, 2024.

[0008] On the other hand, the present disclosure provides a fermentation method of the aforementioned Kluyveromyces marxianus, characterized in that the Kluyveromyces marxianus is fermented in the presence of a nitrogen source and a carbon source, the bacterial cells are collected, and the single-cell protein is separated and purified.

[0009] In another aspect, the present disclosure provides a use of the aforementioned Kluyveromyces marxianus in the preparation and production of β-glucan and / or single-cell protein.

[0010] In another aspect, the present disclosure provides a use of the aforementioned Kluyveromyces marxianus in preparing a food product or a feed additive.

[0011] The beneficial effects of this application are at least as follows:

[0012] The present invention provides a Kluyveromyces marxianus, which is classified and named Kluyveromyces marxianus ( Kluyveromyces marxianus ) CJA0020, and its deposit number is CCTCC No. M 20241673. The Kluyveromyces marxianus strain screened in the present disclosure has a fast growth rate, high protein content, and high β-glucan content, and can be used to widely produce yeast single-cell protein for the preparation of food products or feed additives. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the growth curve of Kluyveromyces marxianus CJA0020 in YPD medium.

[0014] Figure 2 is the β-glucan content of Kluyveromyces marxianus CJA0020. DETAILED DESCRIPTION

[0015] I. Terminology

[0016] In order to make the present disclosure more easily understood, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meaning commonly understood by those skilled in the art to which the present disclosure belongs.

[0017] The term "and / or" should be understood to mean either or both of the alternatives.

[0018] The terms “comprising” or “including” generally imply the inclusion of explicitly stated features, but not the exclusion of other elements.

[0019] The term "about" generally refers to a variation within a range of 0.5%-10% above or below a specified value, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% above or below a specified value.

[0020] As used herein, the expressions "cell," "cell line," and "cell culture" are used interchangeably, and all such names include progeny thereof. Thus, the words "transformants" and "transformed cells" include the primary subject cell and cultures derived therefrom, without regard to the number of transfers. It should also be understood that all progeny may not be exactly identical in terms of DNA content, due to intentional or unintentional mutations. Mutant progeny having the same function or biological activity as screened for in the originally transformed cell are included. Where different names are intended, this is clear from the context.

[0021] "Optional" or "optionally" means that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and where it does not occur.

[0022] The term "fermentation" as used herein refers to the process by which Kluyveromyces marxianus produces the bacteria itself, or direct metabolites or secondary metabolites through life activities under aerobic conditions.

[0023] The term "single cell protein" (SCP) refers to a protein obtained from and / or derived from a (single cell) microorganism. Thus, a single cell protein may refer to a protein purified and / or isolated from, for example, a cell culture of a microorganism. Additionally or alternatively, a single cell protein may refer to a microbial protein that is a dead stem cell of a microorganism. Thus, a "single cell protein product" may or may not include one or more of the following groups: complete (single cell) microbial cells, broken (single cell) microbial cells, isolated proteins obtained by one or more (single cell) microorganisms, isolated proteins derived by one or more (single cell) microorganisms, purified proteins obtained by one or more (single cell) microorganisms, and purified proteins derived by one or more (single cell) microorganisms. Although the (single cell) microorganism may involve bacteria, fungi (such as yeast) and / or algae, the (single cell) microorganism according to the present invention is Kluyveromyces marxianus. Single cell protein products from Kluyveromyces marxianus offer the advantage of providing a relatively high protein content, while at the same time said products can be produced on an industrial scale at relatively low costs, independently of seasonal effects and with relatively small harvesting efforts.

[0024] The present application does not limit the method for collecting bacteria, and conventional methods in the art, such as centrifugation and filtration, can be used. The present application does not limit the method for separation and purification, and conventional methods in the art, such as precipitation, membrane separation, filtration, flocculation, etc., can be used.

[0025] II. Detailed description of embodiments

[0026] In one aspect, the present disclosure provides a Kluyveromyces marxianus, which is classified as Kluyveromyces marxianus ( Kluyveromyces marxianus )CJA0020, its deposit number is CCTCC No. M 20241673.

[0027] When the inventors were isolating and purifying microbial strain resources from Xinjiang Urumqi yogurt, they unexpectedly discovered a strain of Kluyveromyces marxianus, which has a fast growth rate and high β-glucan and protein contents.

[0028] On the other hand, the present disclosure provides a fermentation method of the aforementioned Kluyveromyces marxianus, characterized in that the Kluyveromyces marxianus is fermented in the presence of a nitrogen source and a carbon source, the bacterial cells are collected, and the single-cell protein is separated and purified.

[0029] In some embodiments, the carbon source is selected from one or more of glucose, fructose, sucrose, molasses, maltose, and starch. In some embodiments, the carbon source is glucose. In some embodiments, the concentration of glucose is 40 g / L.

[0030] In some embodiments, the nitrogen source is selected from one or more of corn steep liquor, ammonia water, ammonium sulfate, whey powder, and tryptone. In some embodiments, the nitrogen source is ammonium sulfate. In some embodiments, the concentration of ammonium sulfate is 5 g / L.

[0031] In some embodiments, the mass ratio of the carbon source to the nitrogen source is (1-10): 1. In some embodiments, the mass ratio of the carbon source to the nitrogen source is 1: 1, 2: 1, 3: 1, 4: 1, 5: 1, 6: 1, 7: 1, 8: 1, 9: 1 or 10: 1. In some embodiments, the mass ratio of the carbon source to the nitrogen source is (5-8): 1. The inventors have found that the ratio is conducive to rapid proliferation of bacteria.

[0032] In some embodiments, the fermentation temperature is 25°C to 45°C. In some embodiments, the fermentation temperature is 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C or 45°C. If the fermentation temperature is too low, the fermentation speed will be slow, and if the fermentation temperature is too high, the activity of the bacteria will be affected. The inventors have found that when the fermentation temperature is within the temperature range, it is beneficial to improve the fermentation speed and the quality of the fermentation product.

[0033] In some embodiments, the fermentation time is 24h-60h. In some embodiments, the fermentation time is 24h, 25h, 26h, 27h, 28h, 29h, 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 38h, 39h, 40h, 41h, 42h, 43h, 44h, 45h, 46h, 47h, 48h, 49h, 50h, 51h, 52h, 53h, 54h, 55h, 56h, 57h, 58h, 59h or 60h. The inventors found that if the fermentation time is too short, the yield of the fermentation product is low, and if the fermentation time is too long, the bacterial cell will age, which will affect the quality of the fermentation product.

[0034] In some embodiments, the inoculation amount of the Kluyveromyces marxianus is 0.05%-20%. In some embodiments, the inoculation amount of the Kluyveromyces marxianus is 0.05%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%. In some embodiments, the inoculation amount of the Kluyveromyces marxianus is 2%. If the inoculation amount is too low, it is not conducive to the rapid proliferation of the bacteria. If the inoculation amount is too high, the proliferation rate is too fast, and the bacteria are prone to aging, which affects the quality of the fermentation product.

[0035] In another aspect, the present disclosure provides a use of the aforementioned Kluyveromyces marxianus in the preparation and production of β-glucan and / or single-cell protein.

[0036] In another aspect, the present disclosure provides a use of the aforementioned Kluyveromyces marxianus in preparing a food product or a feed additive.

[0037] In the following detailed description of the embodiments of the present disclosure, reference is made to the accompanying drawings. Similar reference numerals in the accompanying drawings indicate similar elements, and specific embodiments in which the present disclosure can be practiced are shown in the accompanying drawings by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to implement the present disclosure. In other cases, well-known processes, structures, and techniques are not shown in detail to avoid confusing the understanding of this specification. Therefore, the following detailed description should not be understood as limiting, and the technical solutions of the present disclosure are limited only by the attached claims.

[0038] Example

[0039] A further understanding of the present disclosure can be obtained by referring to some specific embodiments given herein, which are only used to illustrate the present disclosure and are not intended to limit the scope of the present disclosure. Obviously, various modifications and changes can be made to the present disclosure without departing from the essence of the present disclosure, and therefore, these modifications and changes are also within the scope of the protection claimed in this application.

[0040] Example 1: Screening and identification of Kluyveromyces marxianus

[0041] 1. Strain screening

[0042] 10 g of yogurt from Urumqi, Xinjiang in June 2023 was added to 90 mL of sterile saline and vortexed for 3-5 min to mix the yogurt thoroughly. The sample was gradient diluted with sterile saline and 10 -2 , 10 -3 , 10 -4 , 10 -5100 μL of the sample in the dilution gradient was spread on KDM screening medium plates (KDM medium formula: yeast extract 5 g / L, peptone 3 g / L, malt extract 3 g / L, glucose 10 g / L, agar 20 g / L, after high-pressure sterilization, filter-sterilized 5-Bromo-4-chloro-3-indolyl β-D-galactopyranoside (X-Gal, a chromogenic substrate for β-galactosidase, which produces a blue product under the catalysis of β-galactosidase), isopropyl-β-D-thiogalactoside (IPTG) and chloramphenicol were added, with final concentrations of 0.08 mg / L, 0.1 mg / L and 0.5 mg / L, respectively), and cultured at 30°C for 48 hours.

[0043] Pick a single blue colony for streak purification. After purification twice, pick a single colony and culture it in YPD liquid culture medium at 30°C, 200 rpm for 16 hours to preserve the final concentration of 20% glycerol for later use.

[0044] 2. Strain Identification

[0045] The preserved strains were identified by colony morphology and molecular biology. Among them, colony morphology includes streaking or diluting on the common yeast solid culture medium YPD to obtain single colony morphology, and its morphological characteristics are: the colonies are larger and thicker than bacterial colonies, the colonies are nearly white or milky white, the surface is smooth, the edges are neat, moist, sticky, easy to pick up, and the texture is uniform. These characteristics are consistent with the colony characteristics of yeast on YPD plates, and can be preliminarily judged as yeast strains. Molecular biological identification includes extracting the genome of the target strain, and amplifying the ITS, 26S and 18S sequences using the genome as a template. After NCBI sequence alignment, the results show that it is Kluyveromyces marxii.

[0046] In summary, the inventors named the strain Kluyveromyces marxianus ( Kluyveromyces marxianus )CJA0020.

[0047] The CJA0020 strain of the present application has been deposited in the China Center for Type Culture Collection (CCTCC, Wuhan University, Wuhan, China) on July 22, 2024, with the deposit number CCTCC No. M 20241673, and is classified as Kluyveromyces marxianus ( Kluyveromyces marxianus )CJA0020.

[0048] Example 2: Growth of Kluyveromyces marxianus CJA0020

[0049] 2.1 Determination of culture medium

[0050] The inventors tested the effects of six different carbon sources, including glucose, fructose, sucrose, molasses, maltose and starch, on the growth of Kluyveromyces marxianus CJA0020 in a shake flask system.

[0051] The results showed that the yeast biomass was the highest when the glucose concentration was 40 g / L; the yeast biomass was the highest when the sucrose concentration was 30 g / L; the yeast biomass was the highest when the fructose concentration was 20 g / L; the yeast biomass was the highest when the molasses concentration was 50 g / L; the yeast biomass was the highest when the maltose concentration was 20 g / L; and the yeast biomass was the highest when the starch concentration was 30 g / L. Taking all factors into consideration, glucose (40 g / L) was the preferred carbon source to detect the growth curve of Kluyveromyces marxianus CJA0020 strain.

[0052] The inventors tested the effects of various organic nitrogen sources (yeast powder, soy peptone, bacterial peptone) 10-50 g / L and inorganic nitrogen sources (ammonium sulfate, urea) 5-30 g / L on the growth of Kluyveromyces marxianus CJA0020. The results showed that the yeast biomass was the highest when the yeast powder concentration was 20 g / L; the yeast biomass was the highest when the soy peptone concentration was 50 g / L; the yeast biomass was the highest when the bacterial peptone concentration was 30 g / L; the yeast biomass was the highest when the ammonium sulfate concentration was 10 g / L; the yeast biomass was the highest when the urea concentration was 15 g / L; the effects of different nitrogen sources on yeast growth were extremely significant. Comprehensive consideration was given to preferably using yeast powder (20 g / L) and bacterial peptone (30 g / L) as nitrogen sources to detect the growth curve of Kluyveromyces marxianus CJA0020 strain.

[0053] In summary, based on the above experimental results, the modified YPD medium, namely glucose (40 g / L), yeast powder (20 g / L) and bacterial peptone (30 g / L), was used as the detection medium to determine the growth curve of Kluyveromyces marxianus CJA0020.

[0054] 2.2 Growth curve of Kluyveromyces marxianus CJA0020

[0055] Strain activation: Pick a single colony of the test strain Kluyveromyces marxianus CJA0020 on the YPD solid plate, inoculate it into a test tube containing 10 mL of YPD liquid culture medium and culture it overnight with shaking. The culture temperature is 30 °C and the shaking speed is 200 rpm. The control strain is other Kluyveromyces marxianus strains screened in the same batch.

[0056] Strain inoculation: The next day, according to the initial OD 600nm=0.1, inoculated overnight activated Kluyveromyces marxianus CJA0020 and control strain into 100 / 250 mL conical flasks of growth curve test medium (40 g / L glucose, 20 g / L yeast powder and 30 g / L bacterial peptone), and cultured at 30°C with a shaking speed of 200 rpm.

[0057] Growth curve: Kluyveromyces marxianus CJA0020 was cultured for a total of 36 h, and samples were taken every 4-8 h to measure the OD of the growing strain. 600nm value and draw its growth curve.

[0058] Growth curve Figure 1 As shown, compared with other representative Kluyveromyces marxianus (XJSMN-01, XJSMN-08, XJSMN-17 and XJSMN-25) screened from the same batch, its biomass after 48 h of culture increased by 46.5%-60% (mass percentage), indicating that Kluyveromyces marxianus CJA0020 has a significant advantage in biomass under this culture condition.

[0059] Example 3: β-Glucan Content of Kluyveromyces marxianus CJA0020

[0060] 3.1 Strain culture

[0061] The Kluyveromyces marxianus strain was cultured using YPD modified medium (40 g / L glucose, 20 g / L yeast powder and 30 g / L bacterial peptone) for 48 h, and then the cells were collected by centrifugation, washed twice with sterile water, freeze-dried using a freeze dryer or dried in a 105°C oven for more than 4 h to obtain freeze-dried powder or dried powder of Kluyveromyces marxianus CJA0020.

[0062] 3.2 β-Glucan extraction

[0063] Take 50 mg of freeze-dried powder or dried powder of Kluyveromyces marxianus CJA0020, add 1 mL of distilled water and 1 g of glass beads with a diameter of 0.45-0.55 mm, and use vortex oscillation to break the cell wall. Specifically, oscillate for 20 s each time, with an interval of 10 s each time, cycle 35 times, and collect the cell wall by centrifugation. The obtained cell wall (10 mg) was first pretreated with 1000 μL of 72% sulfuric acid at room temperature for 3-5 h, diluted to 10 mL, so that the final concentration of sulfuric acid was 4 mol / L, and then acid hydrolyzed at 100 ° C for 4 h and neutralized with NaOH to neutrality. The obtained solution is the β-glucan content solution to be tested.

[0064] 3.3 β-Glucan detection

[0065] The β-glucan samples were detected by HPLC with a Bio-Rad Aminex HPX-87P carbohydrate analysis column and a differential refractive index detector. The other separation conditions were as follows: column temperature 55°C, detection cell temperature 40°C. The mobile phase was 0.1% formic acid, the flow rate was 0.4 mL / min, and the sample injection volume was 10 μL.

[0066] 3.4 β-Glucan Quantification

[0067] Prepare glucose standard solution (10.0 g / L): weigh 1.0 g (accurate to 0.001 g) of glucose dried at 98℃~100℃ for 2 h, dissolve it in water and make up to 100 mL, and shake well.

[0068] Glucose series standard solutions: measure 0.1 mL, 0.25 mL, 0.5 mL, 0.8 mL and 1.0 mL of glucose standard solution respectively

[0069] Add water to a 10 mL volumetric flask and mix thoroughly. Obtain samples with glucose concentrations of 0.1 g / L, 0.25 g / L, 0.50 g / L, 0.80 g / L, and 1.00 g / L, respectively. Use HPLC to detect glucose standard solutions of different concentrations, plot a glucose standard curve with glucose concentration as the horizontal axis and HPLC response value as the vertical axis, and estimate the β-glucan concentration in the sample based on this curve.

[0070] Test results see Figure 2 After 48 h of cultivation, the β-glucan content of Kluyveromyces marxianus CJA0020 reached 1.23±0.06 g / L, while the β-glucan content of other common Kluyveromyces marxianus strains was about 0.81-0.97 g / L. It can be seen that the β-glucan content of Kluyveromyces marxianus CJA0020 is 26%-51% higher than that of common Kluyveromyces marxianus.

[0071] Therefore, Kluyveromyces marxianus CJA0020 has great potential advantages in producing β-glucan.

[0072] Example 4: Detection of single cell protein content of Kluyveromyces marxianus CJA0020

[0073] Kluyveromyces marxianus is a food-grade safe strain listed in China's "List of Bacteria that Can Be Used in Food". It has the characteristics of fast growth rate, high biomass, and a wide substrate spectrum. It can be used to produce yeast single-cell protein and prepare food products or feed additives. The inventor tested the ability of Kluyveromyces marxianus CJA0020 yeast to produce single-cell protein in a 10 L fermenter.

[0074] The specific fermentation detection process is as follows:

[0075] 1. A single colony of K. marxianus CJA0020 on a YPD solid plate was inoculated into a test tube containing 10 mL of YPD liquid medium and cultured overnight with shaking (culture temperature: 30 ℃, shaker speed: 200 rpm) as the primary seed solution.

[0076] 2. Inoculate the first-level seed solution at a 2% inoculation rate into 200 / 500 mL of YPD liquid medium for expansion culture at a temperature of 30 °C and a shaking speed of 200 rpm for 12-18 h as the second-level seed solution.

[0077] 3. The secondary seed liquid was inoculated into a 10 L fermenter at an inoculation rate of 10% for batch fed fermentation. The fermentation carbon source can be selected from one or more of glucose, fructose, sucrose, molasses, maltose, and starch. In this embodiment, glucose (40 g / L) was selected as the carbon source; the fermentation nitrogen source can be selected from one or more of corn syrup, ammonia water, ammonium sulfate, whey powder, and trypsin. In this embodiment, ammonium sulfate (5 g / L) was selected as the nitrogen source; the fermentation temperature conditions were 25-45 ° C, the fermentation speed conditions were 100-600 rpm, and the fermentation time was 24-60 h.

[0078] 4. After the fermentation was completed, the biomass of Kluyveromyces marxianus CJA0020 was tested and the results showed that the wet weight could reach 400 g / kg after 32 h of cultivation. The single-cell protein content of Kluyveromyces marxianus CJA0020 was tested using the Kjeldahl method.

[0079] The results showed that the single cell protein mass percentage of the CJA0020 strain was 45%. It can be seen that the CJA0020 strain has a fast growth rate and high protein content, and can be used to produce yeast single cell protein for the preparation of food products or feed additives.

[0080] In summary, the Kluyveromyces marxianus CJA0020 strain screened from Xinjiang Urumqi yogurt in the present invention has the characteristics of high biomass, high β-glucan content and high protein content, and can be used to produce yeast β-glucan and yeast single-cell protein.

[0081] The above-mentioned embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure shall be subject to the attached claims.

Claims

1. A Kluyveromyces marxianus, whose classification name is Kluyveromyces marxianus CJA0020, and whose deposit number is CCTCC No. M 20241673.

2. The fermentation method of Kluyveromyces marxianus according to claim 1, characterized in that: The Kluyveromyces marxianus is fermented in the presence of a nitrogen source and a carbon source, the bacterial cells are collected, and the single-cell protein is separated and purified.

3. The method according to claim 2, wherein: The carbon source is selected from one or more of glucose, fructose, sucrose, molasses, maltose and starch.

4. The method according to claim 2, wherein: The nitrogen source is selected from one or more of corn steep liquor, ammonia water, ammonium sulfate, whey powder and tryptone.

5. The method according to claim 2, wherein: The mass ratio of the carbon source to the nitrogen source is (1-10):

1.

6. The method according to claim 2, wherein: The fermentation temperature is 25-45°C.

7. The method according to claim 2, wherein: The fermentation time is 24-60 h.

8. The method according to claim 2, wherein: The inoculation amount of the Kluyveromyces marxianus is 0.05%-20%.

9. Use of the Kluyveromyces marxianus according to claim 1 in the preparation and production of β-glucan.

10. Use of the Kluyveromyces marxianus according to claim 1 in the preparation and production of β-glucan and single-cell protein.

11. Use of the Kluyveromyces marxianus according to claim 1 in preparing food products or feed additives.

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