Rhodotorula mucilaginosa source yeast culture as well as preparation method and application thereof

Abstract

The invention provides a rhodotorula mucilaginosa source yeast culture as well as a preparation method and application thereof, and belongs to the technical field of sheep breeding and breeding. The preparation method comprises the following steps: fermenting rhodotorula mucilaginosa CICC 31192 in a fermentation medium to obtain a rhodotorula mucilaginosa source yeast culture; the fermentation culture medium is prepared from 15 to 25 g of soybean meal, 0.15 to 0.25 g of peptone, 0.005 to 0.02 g of monopotassium phosphate and 0.006 to 0.01 g of magnesium sulfate. Researches find that the rhodotorula mucilaginosa source yeast culture has oxidation resistance to sheep livers, promotes lipid metabolism, improves fatty acid composition of the sheep livers, reduces inflammation risks and improves immunity of the sheep, so that healthy growth of the sheep is promoted. The rhodotorula mucilaginosa source yeast culture provides a safe and effective sheep production accelerant, feed additive or medicine for the breeding industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of sheep breeding and cultivation, and particularly relates to a Rhodotorula mucilaginosa - derived yeast culture, a preparation method thereof, and an application thereof. Background Art

[0002] Sheep are the most common domesticated animals, with a plump body, dense wool, a short head, and white hair. Sheep are now raised all over the world. They are timid and docile, and easy to domesticate, and can provide products such as meat and fur for humans. In the practice of sheep farming, there are often a small number of sheep in the flock that seem to have normal diet, but are significantly slower and thinner in growth and development compared to their peers, and some even die of weakness eventually. Moreover, lambs will have various stress responses during weaning. At this stage, weaned lambs often show low immunity, are prone to infection by various pathogens, and antibiotics are commonly used clinically for prevention. However, while antibiotics kill pathogenic bacteria, they also cause problems such as drug residues, bacterial drug resistance, and imbalance of the animal intestinal flora, seriously affecting the healthy development of the livestock industry and endangering public health safety. More and more countries have banned the use of antibiotic products as animal growth promoters, and finding a safe and effective feed additive has become an urgent need in the breeding industry. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a Rhodotorula mucilaginosa - derived yeast culture, a preparation method thereof, and an application thereof. The Rhodotorula mucilaginosa - derived yeast culture has the effects of antioxidant damage to the liver, promoting lipid metabolism, improving fatty acid composition, reducing inflammation, and enhancing immunity.

[0004] In order to achieve the above - mentioned invention purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a preparation method of a Rhodotorula mucilaginosa - derived yeast culture, comprising the following steps:

[0006] Fermenting Rhodotorula mucilaginosa CICC 31192 in a fermentation medium to obtain the Rhodotorula mucilaginosa - derived yeast culture;

[0007] The fermentation medium comprises 15 - 25 g of soybean meal, 0.15 - 0.25 g of peptone, 0.005 - 0.02 g of potassium dihydrogen phosphate, and 0.006 - 0.01 g of magnesium sulfate.

[0008] Preferably, the fermentation temperature is 28 - 32 °C, and the fermentation time is 45 - 50 h.

[0009] The present invention provides a Rhodotorula mucilaginosa - derived yeast culture prepared by the above - mentioned preparation method.

[0010] The present invention provides an application of the above-mentioned Rhodotorula mucilaginosa - derived yeast culture in the preparation of products for promoting the growth of sheep.

[0011] The present invention provides an application of the above-mentioned Rhodotorula mucilaginosa - derived yeast culture in the preparation of products for resisting liver oxidative damage.

[0012] The present invention provides an application of the above-mentioned Rhodotorula mucilaginosa - derived yeast culture in the preparation of products for reducing the blood lipid of sheep.

[0013] Preferably, the Rhodotorula mucilaginosa - derived yeast culture can reduce triglyceride.

[0014] The present invention provides an application of the above-mentioned Rhodotorula mucilaginosa - derived yeast culture in the preparation of products for enhancing the immunity of sheep.

[0015] The present invention provides an application of the above-mentioned Rhodotorula mucilaginosa - derived yeast culture in the preparation of products for treating inflammation.

[0016] The present invention provides a promoter, feed additive or drug for the healthy growth of sheep, wherein the promoter, feed additive or drug comprises the above-mentioned Rhodotorula mucilaginosa - derived yeast culture.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention provides a Rhodotorula mucilaginosa - derived yeast culture, its preparation method and application. It is found that the Rhodotorula mucilaginosa - derived yeast culture has antioxidant ability for the liver of sheep, promotes lipid metabolism, improves the fatty acid composition of the sheep liver, reduces the inflammation risk, enhances the immunity of sheep, and thus promotes the healthy growth of sheep. The Rhodotorula mucilaginosa - derived yeast culture of the present invention provides a safe and effective promoter, feed additive or drug for sheep production in the aquaculture industry. Detailed Embodiments

[0019] The present invention provides a preparation method of a Rhodotorula mucilaginosa - derived yeast culture, comprising the following steps:

[0020] Ferment Rhodotorula mucilaginosa CICC 31192 in a fermentation medium to obtain the Rhodotorula mucilaginosa - derived yeast culture;

[0021] The fermentation medium comprises 15 - 25 g of soybean meal, 0.15 - 0.25 g of peptone, 0.005 - 0.02 g of potassium dihydrogen phosphate and 0.006 - 0.01 g of magnesium sulfate. The water content of the fermentation medium is 50 wt% - 60 wt%.

[0022] In the present invention, Rhodotorula mucilaginosa CICC 31192 is fermented in a fermentation medium to obtain a yeast culture derived from Rhodotorula mucilaginosa. During fermentation culture, the inoculation amount of the Rhodotorula mucilaginosa is 4-6%, further preferably 4.5-5.5%, and more preferably 5%. The inoculation amount refers to the ratio of the volume of the transferred seed liquid to the volume of the medium after inoculation. As a preferred embodiment, the fermentation medium includes 20 g of soybean meal, 0.2 g of peptone, 0.01 g of potassium dihydrogen phosphate, and 0.008 g of magnesium sulfate. The initial pH value of the fermentation medium is 5-7, further preferably 5.5-6.5, and more preferably 6. The Rhodotorula mucilaginosa is a seed liquid of Rhodotorula mucilaginosa. The preparation of the seed liquid includes inoculating Rhodotorula mucilaginosa on a PDA medium for culture to obtain a cultured Rhodotorula mucilaginosa strain, and then inoculating the cultured Rhodotorula mucilaginosa strain on a YPD seed medium for culture to obtain a Rhodotorula mucilaginosa seed liquid. The present invention has no special requirements for the inoculation amount of the seed culture. Just pick a loop of bacteria with an inoculation loop and place it in the seed medium for conventional culture. The temperature of the fermentation is preferably 28-32 °C, further preferably 29-31 °C, and more preferably 30 °C; the fermentation time is preferably 45-50 h, further preferably 46-49 h, and more preferably 48 h. The yeast culture derived from Rhodotorula mucilaginosa obtained by culturing the Rhodotorula mucilaginosa strain of the present invention in the above fermentation medium has antioxidant ability for sheep liver, promotes lipid metabolism, improves the fatty acid composition of sheep liver, reduces the risk of inflammation, and improves the immunity of sheep, thereby promoting the healthy growth of sheep.

[0023] The present invention provides a yeast culture derived from Rhodotorula mucilaginosa prepared by the above preparation method.

[0024] The present invention provides an application of the above yeast culture derived from Rhodotorula mucilaginosa in the preparation of products for promoting sheep growth.

[0025] The present invention provides an application of the above yeast culture derived from Rhodotorula mucilaginosa in the preparation of products for resisting liver oxidative damage.

[0026] The present invention provides an application of the above yeast culture derived from Rhodotorula mucilaginosa in the preparation of products for reducing sheep blood lipid.

[0027] In the present invention, the yeast culture derived from Rhodotorula mucilaginosa can reduce triglyceride.

[0028] The present invention provides an application of the above yeast culture derived from Rhodotorula mucilaginosa in the preparation of products for improving sheep immunity.

[0029] The present invention provides an application of the above yeast culture derived from Rhodotorula mucilaginosa in the preparation of products for treating inflammation.

[0030] In the present invention, the product includes a promoter, a feed additive or a drug.

[0031] The present invention provides a promoter, a feed additive or a drug for promoting the healthy growth of sheep, and the promoter, feed additive or drug includes the above-mentioned Rhodotorula mucilaginosa-derived yeast culture.

[0032] In the present invention, unless otherwise specified, all raw material components are commercially available products well-known to those skilled in the art.

[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0034] In the following embodiments, the PDA medium is prepared by adding 200 g of potatoes, 20 g of glucose, 20 g of agar and 1 L of water, and sterilizing at 115 °C for 20 min.

[0035] The YPD seed medium is prepared by mixing 20 g of glucose, 10 g of peptone, 10 g of yeast extract and 1000 mL of water, and sterilizing at 115 °C for 20 min.

[0036] The fermentation medium is prepared by adding 20 g of soybean meal, 0.2 g of peptone, 0.01 g of potassium dihydrogen phosphate, 0.008 g of magnesium sulfate, adding water to make the water content of the fermentation medium 60 wt%, the initial pH 6.0, and sterilizing at 115 °C for 20 min.

[0037] All experimental procedures involving animals were evaluated and approved by the Animal Welfare and Ethics Committee of Inner Mongolia Agricultural University (No. NND2022110).

[0038] The sheep were purchased from Inner Mongolia Fuchuan Technology Co., Ltd., and the basal diet was purchased from Inner Mongolia Fuchuan Feed Co., Ltd.

[0039] Data analysis: All data were analyzed by one-way analysis of variance using IBM SPSS Statistics 21.0 (SPSS Inc., Chicago, IL, USA) software, and post hoc comparisons were performed using the Duncan method; the tabular data were presented as the mean and the standard error of the mean (SEM), and the graphical data were presented as the mean ± standard deviation (SD). P < 0.05 was defined as a significant difference, and 0.05 ≤ P < 0.1 was defined as a trend of difference. GraphPad Prism 9.5 (GraphPad Software, Boston, USA) was used for plotting.

[0040] Example 1

[0041] Preparation of Rhodotorula mucilaginosa-derived yeast culture:

[0042] (1) Inoculate Rhodotorula mucilaginosa CICC 31192 on PDA medium and culture it at 30 °C. After the strain grows, inoculate it again on YPD seed medium and culture it at a constant temperature of 30 °C in an oscillator at 180 r / min for 24 h to obtain a Rhodotorula mucilaginosa seed solution; there are no strict requirements for the inoculation amount of the seed culture in the present invention. Pick one loop of bacteria with an inoculation loop and put it into the seed medium for conventional culture.

[0043] (2) Inoculate the Rhodotorula mucilaginosa seed solution into the fermentation medium at an inoculation amount of 5%, and ferment at a constant temperature of 30 °C for 48 h to obtain a yeast culture derived from Rhodotorula mucilaginosa (named RYC).

[0044] Example 2

[0045] Application of the yeast culture derived from Rhodotorula mucilaginosa (abbreviated as RYC) prepared in Example 1

[0046] Twenty-four three-month-old Dorper-Han crossbred rams with a body weight of 36 ± 4 kg were selected for the experiment and randomly divided into four groups, with 6 sheep in each group. They were the CON group (fed a basal diet); the L group (fed a basal diet + 10 g / d RYC); the M group (fed a basal diet + 20 g / d RYC); and the H group (fed a basal diet + 40 g / d RYC). The experimental period was 90 days in total, including a 15-day pre-trial period and a 75-day formal trial period. During the experiment, all sheep were fed twice a day at 8:00 and 18:00 and had free access to water. During the pre-trial period, all sheep were only fed the basal diet. Before the formal feeding at 8:00 every day during the formal trial period, the corresponding amount of RYC was fed respectively. On the morning of the last day of the formal trial period, blood was drawn from all sheep before feeding and serum was separated. They were fasted and water-deprived overnight, and the next day, 5 sheep were randomly selected from each group for slaughter and sampling.

[0047] Collect sheep blood from the jugular vein using a disposable vacuum blood collection tube. After standing at room temperature for 40 min, set the centrifuge to 3000 rmp and centrifuge for 10 min. Take the serum and store it in a -20 °C refrigerator for later use. Immediately after the sheep were slaughtered, liver samples were collected, quickly frozen with liquid nitrogen, and then transferred to an -80 °C refrigerator for storage for later use.

[0048] (1) Antioxidant capacity of the liver

[0049] Take 0.2 g of liver sample, add 1.8 mL of normal saline, and prepare a 1:9 liver homogenate. Then put it into a low-temperature centrifuge set at 3000 g, 4 °C, and centrifuge for 10 min. Take the supernatant for later use. T-AOC, CAT, GPx, MDA, SOD, and protein quantification were all measured using commercially available kits (purchased from Nanjing Jiancheng Bioengineering Institute) according to the instructions.

[0050] SOD, GPx, and CAT are three enzymes that play important roles in the antioxidant system. SOD can eliminate superoxide anion radicals to protect cell membranes; GPx and CAT can scavenge H2O2 to protect cell membranes from damage.

[0051] As shown in Table 1, compared with the CON group, the SOD activity in the liver of the H group was significantly increased (P < 0.05); the GPx activities in the L, M, and H groups were all significantly increased (P < 0.05), and there were no significant differences among the three experimental groups; compared with the CON group, the MDA contents in the L, M, and H groups were significantly decreased (P < 0.05), and there were no significant differences among the three experimental groups. There were no significant differences in the liver CAT activity and T-AOC among the groups. This indicates that RYC can enhance the ability of the antioxidant enzyme system in the sheep liver to cope with ROS attack and reduce liver oxidative damage.

[0052] Table 1 Effects of RYC on antioxidant indices in sheep liver

[0053] Item CON L M H SEM P-value SOD (U / mgprot) <![CDATA[196.97 b > <![CDATA[205.09 b > <![CDATA[196.26 b > <![CDATA[223.31 a > 3.745 0.007 CAT (U / mgprot) 36.47 41.79 40.27 37.94 1.086 0.361 GPx (U / mgprot) <![CDATA[10.45 b > <![CDATA[14.62 a > <![CDATA[13.23 a > <![CDATA[13.74 a > 0.573 0.024 T-AOC (μmol / gprot) 72.48 71.50 74.26 73.79 1.311 0.911 MDA (nmol / mgprot) <![CDATA[1.26 a > <![CDATA[0.74 b > <![CDATA[0.78 b > <![CDATA[0.88 b > 0.062 0.022

[0054] (2) Serum lipid metabolism

[0055] The contents of glucose (GLU), total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) were determined according to the instructions of commercially available kits (purchased from Nanjing Jiancheng Bioengineering Institute). Free fatty acids (FFA) were determined by ELISA method (purchased from Baoman Biotechnology Co., Ltd.).

[0056] As shown in Table 2, compared with the CON group, the TC in the L and M groups was significantly decreased (P < 0.05), and there was no significant difference between the L and M groups; compared with the CON group, the LDL-C in the L, M, and H groups was significantly decreased (P < 0.05), but there were no significant differences among the three experimental groups; compared with the CON group, the TG contents in the M and H groups were significantly decreased (P < 0.05), and there was no significant difference between the M and H groups. There were no significant differences in the GLU and FFA contents among the groups. This indicates that RYC can simultaneously reduce the TC and LDL-C contents in the sheep serum and has a tendency to reduce the serum FFA content, indicating that RYC has the effect of regulating sheep lipid metabolism.

[0057] The content of serum GLU can reflect the blood glucose situation of the body, and the blood glucose level of the body is considered to be related to health. The source of GLU in ruminants mainly depends on endogenous synthesis, especially the gluconeogenesis pathway. Therefore, the GLU level can reflect the energy level and health status of livestock and poultry fed with diets for a certain period to a certain extent. In the results, it was found that there were no obvious differences in GLU among the groups, which indirectly proved that there were no differences in energy intake among the sheep in each group in this example, and the experimental results were only related to the effect of adding RYC.

[0058] Table 2 Effects of RYC on serum lipid metabolism indices in sheep

[0059] Item CON L M H SEM P-value GLU (mmol / L) 3.41 3.20 3.34 3.34 0.076 0.841 TC (mmol / L) <![CDATA[3.06 a > <![CDATA[2.46 b > <![CDATA[2.47 b > <![CDATA[2.66 ab > 0.095 0.040 TG (mmol / L) <![CDATA[0.34 a > <![CDATA[0.31 ab > <![CDATA[0.22 c > <![CDATA[0.25 bc > 0.011 0.014 LDL-C (mmol / L) <![CDATA[0.37 a > <![CDATA[0.22 b > <![CDATA[0.25 b > <![CDATA[0.26 b > 0.017 0.013 FFA (mmol / L) 0.57 0.56 0.56 0.53 0.005 0.056

[0060] (3) Liver fatty acid content

[0061] Weigh 0.6 g of liver, add liquid nitrogen and grind it into powder. Add 0.7 mL of 10 mol / L KOH and 5.3 mL of methanol, mix well and place it in a water bath at 55 °C for heating for 1.5 h. During this period, mix well by shaking from time to time. Cool to room temperature, add 0.58 mL of 12 mol / L H2SO4, mix well again and put it in a water bath at 55 °C for heating for 1.5 h. During this period, mix well by shaking from time to time. Cool to room temperature, add 3 mL of n-hexane, vortex and shake for 5 min, centrifuge at 1500 g for 5 min, take 1 mL of the supernatant and filter it through a 0.22 μm organic filter membrane into a sample bottle for determination. Use a 6890N gas chromatograph (Agilent) to determine the fatty acid content. The conditions and procedures for instrument determination refer to the method of Zhao Cun (Zhao Cun. Research on the regulation network of flavor precursor substances in Wuzhumuqin mutton [D]. Inner Mongolia Agricultural University, 2022.).

[0062] The results in Table 3 show that compared with CON, the content of C16:0 in the liver of group M decreased significantly (P < 0.05), and the contents of C18:2n6C and C20:1 increased significantly (P < 0.05); the content of C22:2n6 in group H increased significantly (P < 0.05); there was an upward trend in C18:3n6 in group H (P = 0.05); the content of ΣPUFA in group M increased significantly (P < 0.05). There were no significant differences in the contents of the remaining fatty acids.

[0063] The fatty acids in the animal body mainly come from exogenous daily diet and endogenous de novo synthesis. The main product of de novo synthesis is C16:0. Compared with CON, the content of C16:0 in the liver of sheep in group M decreased significantly, and the content of C18:0 had an upward trend. C18:0 can be converted from C16:0. It shows that adding 20 g of RYC daily can significantly reduce the content of C16:0 in the liver, and it may promote the conversion of C16:0 to C18:0 in the liver. The content of C20:1 in group M was significantly higher than that in CON, while the content of C18:1C had a downward trend, indicating that adding 20 g of RYC daily can promote the conversion of C18:1 to C20:1 in the liver of sheep.

[0064] C18:2n6C can enhance the metabolic adaptability of CD8 T cells and anti-tumor immunity, and can be converted into C18:3n6. C22:2n6 is a PUFA with anti-inflammatory, anti-tumor and antioxidant functions. Compared with the CON group, the levels of C18:2n6C and PUFA in the M group were significantly increased. There was a tendency for an increase in C18:3n6 and a significant increase in C22:2n6 in the H group, indicating that adding 20 g of RYC daily can enhance the ability of the liver to uptake C18:2n6C fatty acids.

[0065] In summary, RYC can improve the ability of the liver to uptake and synthesize PUFA, improve the fatty acid composition of sheep liver, and reduce the risk of inflammation.

[0066] Table 3 Effects of RYC on the fatty acid composition of sheep liver (percentage of total fatty acids, %)

[0067]

[0068]

[0069] ΣSFA = C8:0 + C10:0 + C12:0 + C14:0 + C15:0 + C16:0 + C17:0 + C18:0;

[0070] ΣMUFA = C14:1 + C16:1 + C17:1 + C18:1C + C20:1;

[0071] ΣPUFA = C18:2n6C + C18:3n3 + C18:3n6 + C20:3n3 + C20:3n6 + C22:2n6 + C22:6n3.

[0072] (4) Liver immune cytokines

[0073] Take 0.1 g of liver sample and add 0.9 mL of normal saline to prepare a 1:9 liver homogenate, then place it in a low-temperature centrifuge set at 3000 g, 4 °C, for 10 min, and take the supernatant for use. According to the instructions, use an ELISA kit (purchased from Baoman Biotechnology Co., Ltd.) to measure the contents of IL-1β, IL-6, IL-10, TNF-α, and IFN-γ in the homogenate, and use a protein quantification kit (purchased from Nanjing Jiancheng Bioengineering Institute) to quantify the protein.

[0074] Liver RNA extraction and real-time fluorescence quantitative PCR

[0075] Take 0.05 g of liver and add 1 mL of RNAisoPlus (purchased from Takara). Extract total RNA according to the instructions. Determine the concentration using Implen P330 (purchased from Implen). Reverse transcribe (purchased from AcuRui Bioengineering Co., Ltd.) into cDNA using ABIVeriti 96 (purchased from Thermo Fisher Scientific), and store it at -20 °C for later use. Use β-actin as the internal reference gene, and use LightCycler 480 Ⅱ Instrument (purchased from Roche) to perform qPCR tests (purchased from AcuRui Bioengineering Co., Ltd.) to detect the expression levels of antioxidant, lipid metabolism, and immunity-related mRNAs. The results are calculated by 2 -ΔΔct Calculate. First, search for relevant mRNA sequences in the National Center for Biotechnology Information (NCBI), design primers using the Primer-BLAST function, and send the sequences to BGI (Beijing Genomics Institute) for synthesis. The specific primer information is shown in Table 4.

[0076] Table 4 Primer Information

[0077]

[0078]

[0079]

[0080] To further explore the mechanism of RYC on lipid metabolism in sheep liver, some key enzymes and proteins related to this were selected to measure their mRNA expression levels. Lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) are two enzymes related to fat degradation and play a role in catalyzing the degradation of triglycerides.

[0081] Table 5 shows that compared with CON, the expression levels of the HSL gene in the M and H groups were significantly upregulated (P < 0.05), the expression level of the FABP1 gene was significantly downregulated (P < 0.05), and there was no significant difference between the M and H groups; compared with CON, the expression level of the LPL gene in the M group was significantly upregulated (P < 0.05). The expression levels of the remaining genes did not change significantly.

[0082] Table 5 shows that the expression levels of both LPL and HSL mRNAs in the M group were significantly upregulated compared with CON, indicating that adding 20 g of RYC daily increased the expression of LPL and HSL mRNAs in sheep, increased the activities of LPL and HSL enzymes, catalyzed the degradation of triglycerides, and reduced the serum triglyceride content.

[0083] Fatty acid-binding protein 1 (FABP1) is a protein that can specifically bind long-chain fatty acids within the cell membrane and is involved in fatty acid transport. The results in Table 5 show that compared with the CON group, the expression levels of FABP1 mRNA in the L and M groups both decreased significantly, indicating that RYC can reduce the serum TG and TC contents of sheep by downregulating the expression of FABP1 mRNA in the sheep liver.

[0084] Table 5 Effects of RYC on the expression levels of genes related to lipid metabolism in the sheep liver

[0085] Item CON L M H SEM P-value PPARA 1 1.28 1.35 1.20 0.103 0.666 FASN 1 1.72 2.07 2.63 0.262 0.164 HSL <![CDATA[1 b > <![CDATA[1.51 ab > <![CDATA[1.73 a > <![CDATA[1.96 a > 0.131 0.041 LPL <![CDATA[1 b > <![CDATA[1.07 b > <![CDATA[1.66 a > <![CDATA[0.88 b > 0.109 0.046 ACC 1 1.66 1.58 1.47 0.141 0.361 CPT1β 1 1.24 1.11 1.43 0.105 0.544 SREBP1 1 1.40 1.02 0.93 0.105 0.472 SCD 1 0.89 1.20 1.05 0.185 0.954 FABP1 <![CDATA[1 a > <![CDATA[0.52 b > <![CDATA[0.39 b > <![CDATA[1.05 a > 0.092 0.008

[0086] The results in Table 6 show that compared with the CON group, the contents of TNF-α and IFN-γ in the liver of sheep in the M group decreased significantly (P<0.05), and the other indicators had no significant effects.

[0087] Table 6 Effects of RYC on immune factors in the sheep liver

[0088]

[0089]

[0090] The results in Table 7 show that compared with the CON group, the expression level of TNF-α gene in the liver of the M group was significantly downregulated (P<0.05); the expression levels of IFN-γ genes in the L and M groups were both significantly downregulated (P<0.05), and there was no significant difference between the two groups; compared with the CON group, the expression levels of TLR4 genes in the L, M, and H groups were all significantly downregulated (P<0.05), and there was no significant difference among the three experimental groups. The other indicators had no significant effects. It shows that RYC can reduce the level of pro-inflammatory factors in the sheep liver, alleviate the inflammatory response of sheep, and is beneficial to the health of sheep.

[0091] Table 7 Effects of RYC on the expression levels of genes related to immunity in the sheep liver

[0092] Item CON L M H SEM P-value IL-1β 1 0.92 0.88 1.17 0.053 0.234 IL-6 1 0.89 1.30 1.19 0.108 0.595 IL-10 1 0.61 0.66 0.70 0.067 0.155 TNF-α <![CDATA[1 a > <![CDATA[0.92 a > <![CDATA[0.69 b > <![CDATA[0.94 a > 0.037 0.004 IFN-γ <![CDATA[1 a > <![CDATA[0.59 b > <![CDATA[0.56 b > <![CDATA[0.88 a > 0.087 0.012 TLR4 <![CDATA[1 a > <![CDATA[0.58 b > <![CDATA[0.65 b > <![CDATA[0.74 b > 0.046 0.002

[0093] In summary, RYC can improve the antioxidant capacity of the sheep liver by upregulating the mRNA expression of Nrf2 and related antioxidant enzymes, reduce the blood lipid level of sheep and improve the fatty acid composition of the liver by regulating the expression of genes related to lipid metabolism such as HSL, LPL, and FABP1, and at the same time has a certain beneficial effect on the immune capacity of the sheep liver. The recommended dosage of RYC is 20 - 40 g / d per sheep.

[0094] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a yeast culture derived from Rhodotorula glutinosus, characterized in that: The following steps are involved: fermenting Rhodotorula mucilaginosa CICC 31192 in a fermentation medium to obtain a Rhodotorula mucilaginosa-derived yeast culture; The fermentation medium comprises 15-25 g of soybean meal, 0.15-0.25 g of peptone, 0.005-0.02 g of potassium dihydrogen phosphate and 0.006-0.01 g of magnesium sulfate.

2. The preparation method according to claim 1, characterized in that: The fermentation temperature is 28-32° C., and the fermentation time is 45-50 hours.

3. The Rhodotorula yeast culture obtained by the preparation method according to claim 1 or 2.

4. Use of the Rhodotorula yeast culture according to claim 3 in preparing a product for promoting sheep growth.

5. Use of the Rhodotorula glutinosus-derived yeast culture according to claim 3 in the preparation of a product for resisting liver oxidative damage.

6. Use of the Rhodotorula yeast culture according to claim 3 in preparing a product for lowering blood lipids in sheep.

7. The use according to claim 6, characterized in that: The Rhodotorula yeast culture is capable of reducing triglycerides.

8. Use of the Rhodotorula yeast culture according to claim 3 in preparing a product for improving sheep immunity.

9. Use of the Rhodotorula yeast culture according to claim 3 in preparing a product for treating inflammation.

10. A promoter, feed additive or medicine for healthy growth of sheep, characterized in that: The promoter, feed additive or medicine comprises the Rhodotorula yeast culture according to claim 3.

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