Degradation of cellulose by yarrowia lipolytica and application of improving rumen fermentation rate

Abstract

The application discloses a Yarrowia lipolytica capable of degrading cellulose and application of the Yarrowia lipolytica in improving rumen fermentation efficiency. The Yarrowia lipolytica strain (Yarrowia lipolytica LY6) has been preserved in the China Center for Type Culture Collection, and the preservation number is CCTCC NO: M2025327. The strain is separated and screened from soil around a fermented feed production enterprise, can degrade cellulose and grow in the range of 10-40 DEG C. The application aims at the deficiencies of conventional yeasts, such as the inability to directly degrade cellulose and the anaerobic energy consumption for producing alcohol when the conventional yeasts are used to improve the rumen fermentation rate. The new type of yeast feed additive developed by using the characteristics of the Yarrowia lipolytica, such as strong stress resistance, wide temperature adaptability, the inability to grow anaerobically and the inability to produce alcohol, has the advantages of remarkable effect, low cost and stable action, and has a good market prospect.

Description

Technical Field

[0001] This invention relates to the field of development and application technology of probiotic inoculants for feed, and particularly to a cellulose-degrading Yersinia lipophila and its application in improving rumen fermentation rate. Background Technology

[0002] The rumen harbors a large number of anaerobic microorganisms and is a vital organ in ruminants for breaking down crude fiber and generating volatile fatty acids through microbial fermentation. The rumen epithelium can effectively absorb ions such as sodium, potassium, and chloride, and its absorption rate of volatile fatty acids can reach 75%. Therefore, the degradation of cellulose and the generation rate of volatile fatty acids in the rumen are crucial for improving feed utilization and indirectly affect the health of ruminants. Numerous studies have shown that yeast-based feed additives play an important role in increasing feed intake and digestibility in ruminants, and reducing heat stress. This is mainly because yeast can consume oxygen in the rumen and promote the activity of anaerobic microorganisms such as cellulose-degrading bacteria, lactic acid-utilizing bacteria, and volatile organic acid-producing bacteria.

[0003] Currently, the development and application of such microbial additives mainly rely on conventional yeast strains such as Saccharomyces cerevisiae, which may have the following problems: (1) Yeast can consume oxygen in the rumen, which helps to form an anaerobic environment. However, Saccharomyces cerevisiae can also grow in an anaerobic environment and produce alcohol. This means that yeast competes with anaerobic microorganisms in the rumen for nutrients. The production and accumulation of alcohol may also affect the activity of other anaerobic bacteria and the health of the fed animals. (2) Yeast generally cannot directly utilize cellulose. The degradation of cellulose can only be promoted through the indirect action of other anaerobic microorganisms. The effect of yeast-based feed additives on improving the degradation of cellulose in the rumen of cattle reported in the literature is still not significant. For example, the degradation rate of neutral detergent fiber after 24 hours of feeding is still less than 60%. (3) The optimal growth temperature of yeast is generally 28°C, while the average rumen temperature of ruminants is 39°C. In addition, yeast agents added to feed in cold environments such as winter need to be heated with the digesta to have activity. (4) The saliva secreted by ruminants contains a large amount of carbonates and phosphates. After entering the rumen, it can buffer the pH changes caused by the entry and exit of chyme and the generation and absorption of volatile fatty acids, so that the pH value in the rumen is generally stable in the range of 6 to 7, which is more suitable for yeast growth. However, it also results in a high concentration of salt ions in the rumen and a large osmotic pressure that yeast needs to withstand.

[0004] Yarrowia lipolytica is an unconventional yeast that is tolerant of low temperatures, high salt, and acid, and possesses strong enzyme-producing capabilities. It is highly dependent on oxygen, cannot grow in anaerobic environments, and lacks the ability to produce alcohol anaerobically. It has been recognized as a safe substance by the US FDA and the EU EFSA, and is included in my country's "Feed Ingredient Catalog" and "Feed Additive Catalog." Using metabolic engineering and synthetic biology techniques, Yarrowia lipolytica has been successfully modified to achieve efficient utilization of cellulosic raw materials by engineered strains. If a wild-type (non-genetically engineered) strain of Yarrowia lipolytica capable of degrading cellulose and possessing broad temperature adaptability is screened, and its strong stress resistance, non-anaerobic growth, and lack of alcohol production are utilized, it holds promise for developing a yeast probiotic agent more suitable for promoting rumen fermentation efficiency in ruminants, with promising application prospects. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings of conventional yeasts such as Saccharomyces cerevisiae as microbial additives to promote rumen fermentation efficiency in ruminants, and in particular to develop a yeast probiotic agent that can degrade cellulose and has a wide temperature adaptability, this invention provides a wild-type strain of Yarrowia lipolytica (Yarrowia lipolytica LY6, hereinafter referred to as Yarrowia lipolytica LY6) that can degrade cellulose and a method for improving rumen fermentation efficiency in ruminants.

[0006] The Yarrowia lipolytica strain LY6 was isolated and screened by the inventors from soil surrounding the production site of a fermented feed company in Yichang City, Hubei Province, under conditions below 10℃ through extensive experiments. This company, located in a suburban area, has never conducted research on microbial genetic engineering or has never introduced genetically engineered strains for production. In addition to possessing the basic characteristics of Yarrowia lipolytica, such as strong stress resistance, non-anaerobic growth, and non-alcohol production, strain LY6 can also degrade cellulose and grow within a temperature range of 10–40℃. This strain was deposited on February 28, 2025, at the China Center for Type Culture Collection (CCTCCNO: M2025327), classified as *Yarrowia lipolytica* LY6, at Wuhan University, Wuhan, China.

[0007] This invention also provides a method for isolating and screening *Yersinia lipolytica* strains capable of degrading cellulose and exhibiting broad temperature adaptability from nature. The method includes: sampling soil from the vicinity of a fermented feed production site under low-temperature conditions; resuspending the soil sample in sterile water; diluting the supernatant appropriately and spreading it onto the surface of YPD solid culture medium; and culturing in incubators at 10℃ and 40℃ for 48 hours, respectively. Colonies capable of growing simultaneously at 10℃ and 40℃ are streaked onto the surface of the YPD solid culture medium until single colonies are obtained. Each isolated single colony is inoculated into YPD liquid culture medium and cultured sequentially in a shaker at 10℃ (aerobic) for 12 hours, then transferred to an anaerobic incubator for static culture at room temperature (anaerobic) for 12 hours, and then transferred to a shaker at 40℃ (aerobic) for 12 hours. Single colonies that can grow under aerobic conditions but not under anaerobic conditions and do not produce alcohol are selected for microscopic observation. Single colonies exhibiting typical yeast characteristics are selected for 26S rDNA sequencing, and strains identified as *Yersinia lipolytica* by sequencing results are retained. Each selected *Yarrowia lipolytica* strain was inoculated onto the surface of a solid culture medium with sodium carboxymethyl cellulose as the sole carbon source using a spot method. After the colonies formed distinct colonies, the colony diameter *d* was measured. The solid culture medium plates were then stained and washed with Congo red and sodium chloride solutions, respectively, and the diameter *D* of the resulting transparent zone was measured. Strains with a larger *D* / *d* value and shorter growth time were selected.

[0008] The present invention also provides a liquid inoculum containing the above-mentioned live *Yarrowia lipolytica* strain LY6 (average bacterial concentration 5 × 10¹⁰ cfu / mL). The liquid inoculum containing live *Yarrowia lipolytica* LY6 is a fermentation broth of *Yarrowia lipolytica* LY6 obtained by fed-batch culture in a fermenter using glucose and corn steep liquor powder as raw materials.

[0009] This invention also provides a method for improving rumen fermentation efficiency in beef cattle, specifically the content of volatile fatty acids in rumen fluid and the degradation rate of feed in the rumen, using a liquid inoculum containing the above-mentioned live *Yersinia lipolytica* strain LY6. The method includes: mixing the above-mentioned liquid inoculum containing live *Yersinia lipolytica* strain LY6 at a rate of 1×10¹² cfu per head per day (20 mL total), divided into two doses (10 mL each time) and adding it to the basal diet of Simmental beef cattle. After 7 days of feeding, rumen fluid samples were taken daily for 3 consecutive days to determine the content of volatile fatty acids such as acetic acid, propionic acid, and butyric acid. The degradation rates of dry matter (DM) and neutral detergent fiber (NDF) in the rumen feed were determined using the nylon bag method. The results showed that adding *Yersinia lipolytica* strain LY6 increased the degradation rates of both DM and NDF in the rumen feed by approximately 10%, and the NDF degradation rate exceeded 60% after 14 hours of feeding. The contents of acetic acid, propionic acid and butyric acid in rumen fluid all increased significantly, and the total volatile fatty acids (the sum of the contents of acetic acid, propionic acid and butyric acid) could increase by more than 35% at its highest.

[0010] The application of the cellulose-degrading Yarrowia lipolytica LY6 proposed in this invention to improve rumen fermentation rate has the following beneficial effects: The cellulose-degrading Yarrowia lipolytica LY6 provided by this invention can directly degrade cellulose and use it as a carbon source for growth, overcoming the shortcomings of existing brewing yeasts that cannot directly utilize cellulose and can only indirectly promote cellulose degradation, thereby significantly improving the rumen's utilization efficiency of crude fiber feeds.

[0011] The strain described in this invention has a wide temperature adaptability range (10-40℃), and can not only maintain its activity at low temperatures, but also grow stably at temperatures close to the actual rumen temperature, thus solving the problem of insufficient activity of existing yeast strains in actual feeding environments.

[0012] The *Yersinia lipolytica* described in this invention is a strict aerobic bacterium that cannot grow under anaerobic conditions and does not produce alcohol. This avoids the problems of existing brewing yeasts producing alcohol, inhibiting the activity of beneficial anaerobic bacteria, and affecting animal health in the rumen anaerobic environment, and is conducive to maintaining the stability of the rumen microecology.

[0013] The strain described in this invention has good salt tolerance, acid tolerance, and osmotic pressure resistance, and can adapt to the high salt ion and buffer system environment in the rumen, thereby improving the survival rate and stability of the bacteria in the rumen. Attached Figure Description

[0014] Figure 1 This is the phylogenetic tree constructed based on the gene sequencing results of strain LY6 in Example 1; Figure 2 The transparent zone formed by culturing Yersinia lipolytica strain LY6 on the surface of a solid culture medium with sodium carboxymethyl cellulose as the sole carbon source for 5 days, followed by Congo red staining and rinsing with sodium chloride solution; Figure 3 The changes in acetic acid content in the rumen fluid of cattle after morning feeding in the experimental and control groups of Example 3 over time; Figure 4 The changes in propionic acid content in the rumen fluid of cattle after morning feeding in the experimental and control groups of Example 3 over time; Figure 5 The butyric acid content in the rumen fluid of cattle after morning feeding in the experimental and control groups of Example 3 changes over time. Figure 6 The total volatile fatty acid content in the rumen fluid of cattle after morning feeding in the experimental and control groups of Example 3 changes over time. Detailed Implementation

[0015] The present invention will be further explained below with reference to the embodiments and accompanying drawings. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0016] Example 1: Isolation and screening of Yersinia lipolyticis, a cellulose-degrading yeast with a wide temperature adaptability Isolation of Yersinia lipolytica, exhibiting broad temperature adaptability: 100g of topsoil (2-5cm deep) was collected from the vicinity of a fermented feed production site in Yichang City, Hubei Province, and brought back to the laboratory. 5g of the soil sample was placed in an Erlenmeyer flask containing 50mL of sterile water, shaken at 200rpm at room temperature for 30min, and then allowed to stand. The supernatant was collected as a bacterial suspension. 10mL of the bacterial suspension was added to a sterile test tube and diluted 10⁷ times with sterile water. 0.1mL of the diluted solution was spread onto the surface of YPD solid medium (10g yeast extract, 20g peptone, 20g glucose, 20g agar, 1L deionized water, pH 6.8, sterilized at 115℃ for 30min), and incubated at 10℃ and 40℃ for 48h respectively. Colonies capable of growing simultaneously at 10℃ and 40℃ were picked and streaked onto fresh YPD solid medium until single cells were obtained. Each isolated single bacterium was inoculated into YPD liquid medium (excluding agar, otherwise the same as YPD solid medium), and cultured sequentially at 10℃ and 200 rpm (aerobic) for 12 h in a shaker, then transferred to an anaerobic incubator for 12 h at room temperature (anaerobic), and finally transferred to a 40℃ shaker for 12 h in aerobic mode. During the culture process, samples were taken every 4 h to measure changes in cell concentration (OD600 absorbance) and ethanol concentration in the culture medium (headspace gas chromatography). Single bacteria that could grow under aerobic conditions but not under anaerobic conditions and did not produce alcohol were selected for observation under a 40x optical microscope. Single bacteria with typical yeast characteristics were selected for 26S rDNA sequencing, and strains identified as *Yersinia lipolytica* were retained. Through the above operations, a total of 16 *Yersinia lipolytica* strains capable of growing in the range of 10–40℃ were isolated, named strains LY1–LY16. The phylogenetic tree based on the sequencing results of strain LY6 was constructed by sequence alignment using the NCBI website, as shown below. Figure 1 As shown, it has 100% homology with Yarrowia lipolytica, proving that strain LY6 is Yarrowia lipolytica.

[0017] Screening of *Yersinia lipolytica* strains capable of degrading cellulose: The isolated *Yersinia lipolytica* strains LY1-LY16 were inoculated onto the surface of a solid culture medium with sodium carboxymethyl cellulose as the sole carbon source (20 g sodium carboxymethyl cellulose, 2.5 g peptone, 0.5 g yeast extract, 0.5 g KH₂PO₄, 0.5 g K₂HPO₄, 20 g agar, 1 L deionized water, pH adjusted to 7.2, sterilized at 121℃ for 20 minutes) and incubated statically at 28℃. The time required for colonies with a diameter of approximately 1 cm to form and the colony diameter *d* were recorded. The colonies were stained with 1 mg / mL Congo red solution for 15 minutes and destained with 1 mol / L NaCl solution for 1 hour, and the diameter *D* of the transparent zone formed around the colonies was measured, and the *D* / *d* ratio was calculated. The results are shown in Table 1. A total of four *Yersinia lipolytica* strains were able to grow on the surface of the solid culture medium with sodium carboxymethyl cellulose as the sole carbon source and form a transparent zone. Among them, the Yersinia lipolyticis strain LY6 required the shortest growth time and had the largest ratio of the diameter D of the transparent zone to the diameter d of the colony. Figure 2 This indicates that strain LY6 has the strongest ability to degrade cellulose, therefore this strain was selected for further research.

[0018] Table 1. Cellulose Degradation Capacity of Some Yersinia lipolytica Strains

[0019] Example 2: Preparation of a liquid inoculum containing live *Yarrowia lipolyticis* strain LY6 Liquid aerobic fermentation of *Yarrowia lipolyticis* strain LY6 was conducted in a 5L fermenter. After extensive experiments, the optimal fermentation conditions for strain LY6 were determined as follows: The fermentation medium consisted of 10.5 g / L glucose and 8.4 g / L corn steep liquor powder. The initial pH of the fermentation broth was adjusted to 6.4 using NaOH, and the pH was stabilized at approximately 6.4 during fermentation via automatic pH control. The fermentation broth volume was 3L. After sterilization at 115℃ for 30 minutes, 5% of the fermentation broth volume of strain LY6 was inoculated into shake flasks. During the early stages of fermentation, dissolved oxygen was controlled by adjusting the fermenter's stirring speed. The initial speed was 150 rpm, and the speed was increased by 50 rpm each time the dissolved oxygen level dropped to 10%, with a maximum stirring speed of 300 rpm. During the later stages of fermentation, dissolved oxygen was controlled by feeding. Feeding was initiated when the dissolved oxygen level reached 30% and stopped when it dropped to 10%. The feed solution consisted of 50 g / L glucose and 21 g / L corn steep liquor powder, with a volume of 0.7 L. After fermentation under these conditions for 30 hours, the number of viable bacteria in the fermentation broth was determined by plate count. The fermentation broth obtained by the above method is a liquid inoculum containing live *Yarrowia lipolyticis* strain LY6, with an average viable count of 5 × 10¹⁰ cfu / mL.

[0020] Example 3: Verification of the effect of liquid bacterial agent containing live Yeast LY6 on improving rumen fermentation efficiency in beef cattle The feeding experiment was conducted in December 2025 at a cattle farm in Hangzhou with animal testing qualifications. The experiment lasted for 10 days, with an average temperature of 9.8℃. Six Simmental beef cattle of similar age and weight, in good health, and equipped with rumen fistulas were selected and divided into an experimental group and a control group. Three cattle from each group were randomly selected and fed separately in the same shed. The control group was fed a basal diet, while the experimental group was fed a liquid bacterial agent containing live Yersinia lipolytica LY6 at a rate of 1×10¹² CFU per head per day, totaling 20 mL, after mixing it into their basal diet. The feeding times (8:00 AM and 3:00 PM twice a day, with free access to water) and basal diet formulas (55% silage, 20% soybean meal, 10% distillers' grains, 9% wheat bran, 5% corn, salt, and 1% premix) were the same for both the experimental and control groups. The only difference was that the experimental group received 10 mL of the liquid bacterial agent each time. For the first 7 days of the experiment, the diet was fed without sampling to allow the *Yersinia lipolytica* LY6 in the inoculum to colonize the rumen and stabilize the rumen microbial community. For the last 3 days of the feeding experiment, 20 mL of rumen fluid was collected daily before morning feeding (0h) and at 4, 8, and 14 hours after morning feeding via a rumen fistula. After centrifugation at 4000 rpm for 5 minutes at 4°C, the contents of acetic acid, propionic acid, and butyric acid were determined by headspace gas chromatography. The total volatile fatty acid (VFA) content was equal to the sum of the contents of acetic acid, propionic acid, and butyric acid. The degradation rates of dry matter (DM) and neutral detergent fiber (NDF) in the rumen were determined using the nylon bag method. The nylon bags had a pore size of 300 mesh, and each bag contained 5 g of a basal diet without *Yersinia lipolytica* LY6 inoculum. Every morning before feeding (0h), a nylon bag was placed into the rumen through a fistula. Three nylon bags were removed at 4, 8, and 14 hours after feeding, immediately rinsed with deionized water, and dried in a 65℃ oven until constant weight. The contents of the dried nylon bags from each cow were ground into a single mortar and pulverized in the same container. After thorough mixing, the powder was sieved through a 40-mesh sieve. The resulting powder samples were then analyzed for DM and NDF content using methods specified in national standards GB / T6435-2014 and GB / T20806-2022. The degradation rate of DM or NDF at a given time point was calculated as: (DM or NDF content of the original basal diet - DM or NDF content of the sample taken from the nylon bag at that time point) / DM or NDF content of the original basal diet × 100%. The average value of the test results taken from each cow in the experimental and control groups at a certain time point each day for the last 3 days was used to analyze and represent the stability of the effect of improving rumen fermentation efficiency in beef cattle (if the difference in a certain test result at a certain time point each day for the last 3 days exceeds 30% between the experimental and control groups, the effect is considered unstable). In addition, since the morning feeding time is 14 hours, and considering that continuing to sample would affect the sleep of the experimental beef cattle, which may be detrimental to the animals' health and thus affect the measurement results of normal rumen fermentation efficiency, sampling was stopped 14 hours after the morning feeding each day.

[0021] Table 2. Degradation rates of dry matter (DM) and neutral detergent fiber (NDF) in the rumen of the diet.

[0022] The changes in DM content and degradation rate in the basal diet can basically represent feed utilization. NDF includes components such as hemicellulose, cellulose, lignin, and silicates, and changes in their content can more accurately reflect the degradation of feed fiber. As shown in Table 2, the error between the test results at a certain time point each day for 3 days after feeding in the experimental and control groups was within 10%, indicating that the data obtained from the feeding experiment were stable and representative. The degradation rates of DM and NDF in the rumen of the experimental group at each time point were about 10% higher than those of the control group at the same time point. Moreover, after feeding the basal diet with Yersinia lipolyticis strain LY6, the NDF degradation rate exceeded 60% after 14 hours. This may be the most direct manifestation of the ability of Yersinia lipolyticis strain LY6 to degrade cellulose and promote the degradation of feed fiber in the rumen.

[0023] Figures 3 to 6 The changes in acetic acid, propionic acid, butyric acid, and total volatile fatty acid (VFA) content in the rumen fluid of beef cattle in the experimental and control groups after morning feeding over time were shown. At each time point, the acetic acid, propionic acid, and butyric acid content in the rumen fluid of the experimental group were significantly higher than those in the control group at the same time point. Furthermore, the total VFA content (the sum of acetic acid, propionic acid, and butyric acid) in the experimental group was at its highest level more than 35% higher than that in the control group at the same time point. Combined with the feed degradation rate results in Table 2, this indicates that mixing a liquid inoculum containing live *Yarrowia lipolyticis* strain LY6 at a dosage of 1 × 10¹² CFU per head per day into the basal diet after feeding can significantly improve feed utilization in the rumen, especially promoting the degradation of feed fiber and significantly increasing the content of easily absorbed volatile fatty acids in the rumen fluid.

[0024] The content of acetic acid, propionic acid, and butyric acid showed different trends over time because these three acids are produced by different types of microorganisms. Although acetic acid is a metabolic byproduct of some anaerobic microorganisms, it is mainly produced by aerobic or facultative anaerobic microorganisms. During feeding, oxygen enters the rumen with the chewing and swallowing of ruminants, so the activity of aerobic or facultative anaerobic microorganisms in the rumen is high within 0-4 hours after feeding, and the acetic acid content increases accordingly. After 4 hours, as oxygen is consumed, the production of acetic acid decreases and it is gradually absorbed by the rumen, leading to a gradual decrease in the acetic acid content in the rumen fluid. The *Yarrowia lipolytica* strain LY6 can degrade cellulose, providing other microorganisms with higher-quality carbon sources such as monosaccharides and oligosaccharides, and consuming the limited oxygen in the rumen. Therefore, the experimental group had a higher acetic acid content, and the acetic acid content showed a decreasing trend earlier. Propionic acid is produced by facultative or strict anaerobic microorganisms, while butyric acid can only be produced by strict anaerobic microorganisms. Therefore, the levels of propionic acid and butyric acid in the rumen fluid did not increase significantly from 0 to 4 hours after feeding; in fact, they even showed a decreasing trend as the rumen absorbed these two acids. In contrast, the levels of propionic acid and butyric acid in the rumen fluid of the experimental group increased significantly after 4 or 8 hours, while the levels of propionic acid and butyric acid in the rumen fluid of the control group generally showed a decreasing trend. This is because the addition of *Yarrowia lipolytica* strain LY6 can promote the growth of facultative and strict anaerobic microorganisms that produce propionic acid and butyric acid in the rumen during the later stages. Even though propionic acid and butyric acid in the rumen fluid are continuously absorbed, their levels still show an increasing trend.

[0025] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A cellulose-degrading Yersinia lipolyticis yeast, characterized in that, Yarrowia lipolytica LY6 was inoculated into glucose corn steep liquor medium and fermented under fed-batch conditions of pH 6.4, fermentation temperature 28℃, and stirring speed 150~300 rpm.

2. The cellulose-degrading Yersinia lipolyticis yeast according to claim 1, characterized in that, The glucose-corn steep liquor liquid culture medium comprises 10.5 g / L glucose and 8.4 g / L corn steep liquor powder, adjusted to pH 6.4 and sterilized. The fed-batch fermentation broth comprises 50 g / L glucose and 21 g / L corn steep liquor powder, adjusted to pH 6.4 and sterilized.

3. The lipophilic yeast of claim 2, characterized in that, Its fermentation broth is used as a feed microbial additive to improve the utilization rate of feed in the rumen of cattle.

4. The lipophilic Yeast strain for degrading cellulose according to claim 3, characterized in that, Application of Yarrowia lipolytica LY6 or its fermentation broth as a feed microbial additive to increase the content of volatile fatty acids such as acetic acid, propionic acid, and butyric acid in bovine rumen fluid.

5. The cellulose-degrading Yersinia lipolyticis yeast according to claim 4, characterized in that, Application of Yarrowia lipolytica LY6 or its fermentation broth as a feed microbial additive to improve the fermentation efficiency in the rumen of cattle.

6. The application of the cellulose-degrading Yersinia lipolytica according to claim 3, 4, or 5, characterized in that, The Yarrowia lipolytica LY6 or its fermentation broth is added to the daily ration of beef feed and fed twice a day, in the morning and evening.

7. The application of the cellulose-degrading Yersinia lipolyticis yeast according to claim 6, characterized in that, The dosage of Yarrowia lipolytica LY6 or its fermentation broth is 1×10⁻⁶ per organism per day. 12 CFU.

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