Yeast protein-dietary fiber compound as well as preparation method therefor and use thereof

Abstract

A preparation method for a yeast protein-dietary fiber compound, comprising: pretreating a biomass raw material, and then sequentially carrying out steam explosion treatment, water washing treatment, delignification treatment, low-enzyme-amount enzymatic hydrolysis, fed-batch liquid fermentation and spray drying treatment to obtain a yeast protein-dietary fiber compound. Also provided are a product prepared by using the preparation method, the use of the product, and a feed comprising the product.

Description

Yeast protein-dietary fiber complex and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of feed processing, in particular to a yeast protein-dietary fiber complex and a preparation method and application thereof. Background Art

[0002] my country possesses abundant carbohydrate biomass resources, such as straw and forestry byproducts. my country produces 1 billion tons of crop straw annually, of which only 34% is used for livestock production, and the utilization rate is less than 50%. Straw biomass is primarily composed of cellulose, hemicellulose, and lignin. Cellulolytic bacteria or cellulase act on woody fiber raw materials, converting cellulose and hemicellulose into monosaccharides or oligosaccharides, primarily glucose and xylose. These are then fermented to produce high-value-added products such as ethanol, xylitol, and organic acids, or directly cultured to produce single-cell proteins. The remaining enzymatically hydrolyzed lignin can be further processed into surfactants, adhesives, pesticides, or slow-release fertilizers, thereby increasing the utilization rate of woody biomass resources.

[0003] The global population is projected to reach 9.7 billion by 2050. Based on current consumption levels, 1.25 billion tons of meat and dairy products will be needed annually to meet the demand for animal-based protein. However, the conversion efficiency of traditional plant proteins is generally low, requiring approximately 6 kg of plant protein to convert to 1 kg of meat protein. Therefore, simply increasing the production of plant protein and animal products to meet demand is unsustainable. my country's soybean demand reached 119.93 million tons in 2020, but domestic production is less than 20 million tons annually, with over 85% of soybeans imported. my country's severe shortage of protein feed resources and high dependence on imports have become a bottleneck restricting the development of the feed and livestock industries. Therefore, identifying protein resources and solutions is crucial to improving my country's self-sufficiency in feed protein and sustainable livestock production.

[0004] Summary of the Invention

[0005] The present invention aims to provide a yeast protein-dietary fiber complex, its preparation method, and its application, to address the aforementioned problems of the prior art. The present invention seeks a new source of dietary fiber and protein. The yeast protein-dietary fiber complex provided by the present invention has a crude protein content of 31%, a total dietary fiber content of 44%, aflatoxin content of <2 μg / kg, and zearalenone content of <10 μg / kg, thereby improving my country's feed protein self-sufficiency and sustainable livestock production.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a method for preparing a yeast protein-dietary fiber complex, comprising the following steps:

[0008] After the biomass raw material is pretreated, steam explosion treatment, water washing treatment, delignification treatment, low enzyme dosage enzymatic hydrolysis, fed-batch liquid fermentation and spray drying treatment are carried out in sequence to obtain a yeast protein-dietary fiber complex;

[0009] The enzyme used in the low-enzyme enzymolysis is cellulase; the dosage of the cellulase is 1.5FPU / g-3.5FPU / g.

[0010] Preferably, the pH value of the low enzyme dosage enzymolysis is 4.8-5.8, the time is 16-72 hours, and the temperature is 45-55°C.

[0011] Preferably, the fed-batch liquid fermentation comprises: diluting a portion of the enzymatic hydrolysate obtained by low-enzyme enzymatic saccharification, and mixing the dilution with (NH4)2SO4, KH2PO4 and MgSO4·7H2O to prepare an initial culture medium;

[0012] The concentration of glucose in the initial culture medium is 40 g / L, the concentration of (NH4)2SO4 is 2.2 g / L, the concentration of KH2PO4 is 2.0 g / L, and the concentration of MgSO4·7H2O is 1.0 g / L;

[0013] Candida utilis is inoculated into the initial culture medium for fermentation and culture, and the remaining enzymatic hydrolysis solution obtained by enzymatic saccharification with a low amount of enzyme is added to the initial culture medium at a flow rate of 10-30 L / min.

[0014] Preferably, during the inoculation, the inoculation volume is 5% of the initial culture medium volume;

[0015] The temperature of the fed-liquid fermentation is 30-35° C.; the termination standard of the fed-liquid fermentation is that the dissolved oxygen content of the fermentation liquid obtained by the fermentation reaches 80-90%.

[0016] Preferably, the temperature of the steam explosion treatment is 180-212°C, and the pressure maintenance time is 3-5 minutes;

[0017] The water washing treatment is carried out at a temperature of 60-100° C., a rotation speed of 200 rpm, and a time of 1 hour.

[0018] The mass percentage of KOH in the KOH solution used in the delignification treatment is 6-10%; the temperature of the delignification treatment is 100° C. and the rotation speed is 200 rpm.

[0019] Preferably, before the spray drying process, the fermentation liquid obtained by the feeding liquid fermentation is centrifuged.

[0020] Preferably, the pretreatment includes the steps of crushing the biomass raw material, mixing and soaking it with acid solution, and then centrifuging it.

[0021] Further preferably, the particle size of the pulverized biomass raw material obtained after the pulverization is 1-10 mesh; the acid solution is a dilute sulfuric acid solution with a mass percentage concentration of 0.1-0.3% (w / w); and the soaking time is 12 hours;

[0022] The biomass raw material includes one or more of wheat straw, rice straw, corn straw, corn cob and bagasse.

[0023] The present invention provides a yeast protein-dietary fiber complex prepared by the above method.

[0024] The present invention provides the use of the yeast protein-dietary fiber complex in preparing feed having the effects of improving sow constipation and / or reducing diarrhea in weaned piglets.

[0025] The present invention provides a feed rich in protein and dietary fiber, wherein the effective ingredients include the yeast protein-dietary fiber complex.

[0026] The present invention discloses the following technical effects:

[0027] From the perspective of animal nutrition, the present invention uses steam explosion treatment to first convert hemicellulose in straw-like biomass into oligosaccharides (prebiotics) or xylose; the separation of the remaining pulp further separates cellulose and lignin, and produces yeast protein-dietary fiber (β-glucan) complexes through a low-enzyme enzymatic fermentation process, which is comprehensively utilized and developed to solve the cost problem of enzymes in the steam explosion-cellulase combined treatment of biomass raw materials, laying the foundation for the industrial production of this technology. At the same time, the steam explosion-enzymatic hydrolysis-fermentation process can convert non-edible biomass raw materials into high-value-added prebiotics and yeast protein-dietary fiber complexes, and does not directly compete with humans for food, opening up a new solution for self-sufficiency and sustainable development of dietary fiber and protein. It can be seen that the present invention efficiently utilizes the carbon source in straw-like biomass to solve the core problem of biorefining of biomass raw materials (the cost problem of enzymes).

[0028] The yeast protein-dietary fiber complex has the nutritional value of dietary fiber, protein and vitamins, and also has the functional value of plant dietary fiber, yeast oligosaccharides and yeast peptides, making it possible to use it as a high-quality dietary fiber and protein raw material in livestock and poultry feed production. A novel yeast protein-dietary fiber complex is obtained by the preparation method of the present invention. The crude protein content in the yeast protein-dietary fiber complex can reach 30%, and it has a balanced amino acid composition, which can meet the amino acid needs of animal husbandry production. At the same time, it contains a relatively high total dietary fiber of up to 43%, and its mycotoxins are all below the detection line. During the application process of the present invention, it was found that the yeast protein-dietary fiber complex of the present invention can replace 7% of the protein source and 5% of the dietary fiber source in the formula, and can improve constipation, inflammation, immunity and intestinal tissue morphology of periparturient sows and reduce diarrhea in weaned piglets. It can be seen that the yeast protein-dietary fiber complex can be used as a nutritional source of protein source and dietary fiber source for monogastric animals. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] FIG1 is a flow chart of the preparation of yeast protein-dietary fiber complex;

[0031] Figure 2 shows the average daily milk production, where L1-7d is the 1st to 7th day of lactation, L8-14d is the 8th to 14th day of lactation, and L15-18d is the 15th to 18th day of lactation;

[0032] Figure 3 shows the sow constipation index (A) and the endotoxin content in sow feces (B), where G113d is the 113th day of gestation and L4d is the 4th day of lactation;

[0033] FIG4 shows the concentration of plasma IgM (A) and the concentration of plasma IL10 (B), where G113d is the 113th day of pregnancy and L18d is the 18th day of lactation. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] Example 1

[0040] A method for preparing a yeast protein-dietary fiber complex comprises the following steps:

[0041] (1) Raw material pretreatment: The wheat straw was crushed to a particle size of 1 mesh, mixed with a dilute sulfuric acid solution with a mass percentage concentration of 0.1%, and the mass volume ratio of the wheat straw powder to the dilute sulfuric acid solution was 1.02 g:1 L. The mixture was soaked for 12 h, centrifuged at 2000 rpm for 5 min, and dehydrated to obtain the material treated with dilute sulfuric acid.

[0042] (2) Steam explosion treatment (steam explosion treatment): The material treated with dilute sulfuric acid was subjected to steam explosion treatment at a steam explosion temperature of 180°C, 1 MPa, and a pressure maintenance time of 3.2 min. After the steam explosion, the material was quickly released to normal pressure to obtain steam-exploded biomass.

[0043] (3) Washing treatment of solid slurry after steam explosion treatment: The steam-exploded biomass was washed twice with 5 times the volume of water (80°C, 200 rpm, 1 h), and the hemicellulose solubilized part was washed into the washing liquid, filtered and separated, and the solid part was the solid slurry after washing. This step effectively separated the hemicellulose into xylose, and realized the maximum value of hemicellulose refining from the steam-exploded biomass. The liquid part (separated liquid part) was filtered and separated, and after membrane concentration (condition parameters were microfiltration, 0.1 μm, 1-2 bar; nanofiltration, 1-10 nm, 5-25 bar; reverse osmosis, ≤1 nm, 10-80 bar), the concentrated liquid (the concentrated liquid containing xylose, XOS DP>6 (23.6 mg / mL) and XOS 2-6 (28.7 mg / mL)) was enzymatically hydrolyzed (conditions: xylanase dosage of 1000 IU / kg, 50°C for 12 h) and purified (conditions: 10% activated carbon; microfiltration, 0.1 μm, 1-2 bar) to obtain xylose or XOS 2-6 .

[0044] (4) Delignification treatment: The solid phase pulp after water washing is delignified by KOH and filter-pressed to obtain cellulose pulp. The conditions are 10 (w / w)% KOH, 100°C, 200 rpm, 1 hour. This step separates cellulose and lignin.

[0045] (5) Low enzyme dosage enzymatic saccharification (low enzyme dosage hydrolysis): Cellulase was added to the obtained cellulose pulp to make the enzymatic activity of the cellulase in the cellulose pulp 3.5 FPU / g, the pH was controlled at 5.8, the enzymatic hydrolysis was carried out at 50°C for 36 hours, the rotation speed was 200 rpm, and an enzymatic hydrolyzate was obtained.

[0046] (6) Fed-batch fermentation: a portion of the enzymatic hydrolysate was diluted and mixed with (NH4)2SO4, KH2PO4, and MgSO4·7H2O to obtain an initial culture medium containing 40 g / L glucose, 2.2 g / L (NH4)2SO4, 2.0 g / L KH2PO4, and 1.0 g / L MgSO4·7H2O.

[0047] The initial culture medium was inoculated with Candida utilis for fermentation, with the inoculation amount being 5% of the culture medium volume, and the remaining enzymatic hydrolysate was fed at a rate of 10 L / min, and fermented at 30° C. for 12-24 hours until the dissolved oxygen content reached 80%, thereby completing the fermentation and obtaining a fermentation broth.

[0048] (7) Spray drying: The fermentation broth is centrifuged, autolyzed and broken, and spray dried in sequence to obtain a yeast protein-dietary fiber complex. The centrifugation condition parameters are: 6000 rpm, the centrifuged concentrate is heated to 55°C, the pH is 5.8, and maintained for 6 hours to achieve yeast cell autolysis (autolysis and wall breaking), and then spray dried. The spray drying condition parameters are: inlet temperature 190°C, outlet temperature 85-95°C.

[0049] The components in the prepared yeast protein-dietary fiber complex were tested, and the test results are shown in Table 1.

[0050] Table 1 Detection results of wheat straw yeast protein-dietary fiber complex components Note: DM: dry matter; CP: crude protein; GE: gross energy; OM: organic matter; NDF: neutral detergent fiber; ADF: acid detergent fiber; TDF: total dietary fiber; SDF: soluble dietary fiber; IDF: insoluble dietary fiber, same as the table below.

[0051] As shown in Table 1, the crude protein content of the yeast protein-dietary fiber complex is 30.57%, the total dietary fiber content is 44%, aflatoxin is less than 2 μg / kg, and zearalenone is less than 10 μg / kg.

[0052] Example 2

[0053] A method for preparing a yeast protein-dietary fiber complex comprises the following steps ( FIG1 ):

[0054] (1) Raw material pretreatment: The corn cob was crushed to a particle size of 3 mesh, mixed with a dilute sulfuric acid solution with a mass percentage concentration of 0.16%, and the mass volume ratio of the corn cob to the dilute sulfuric acid solution was 1.63 g:1 L. The mixture was soaked for 12 h, centrifuged at 2000 rpm for 5 min, and dehydrated to obtain the material treated with dilute sulfuric acid.

[0055] (2) Steam explosion treatment: The material treated with dilute sulfuric acid was subjected to steam explosion treatment at a temperature of 188°C, 1.2 MPa, and a pressure maintenance time of 3.6 min. After the steam explosion, the material was quickly released to normal pressure to obtain steam-exploded biomass.

[0056] (3) Washing treatment of solid slurry after steam explosion: The biomass treated by steam explosion was washed twice with 5 times the volume of water (60℃, 200rmp, 1h), filtered and separated, and the solid part was the solid slurry after washing, which effectively separated hemicellulose into oligoxylose and realized the maximum value of hemicellulose refining from the biomass treated by steam explosion. The liquid part (separated liquid part) was filtered and separated, and after membrane concentration (condition parameters were microfiltration, 0.1μm, 1-2bar; nanofiltration, 1-10nm, 5-25bar; reverse osmosis, ≤1nm, 10-80bar), the concentrated liquid (the concentrated liquid containing xylose, XOS) was concentrated. DP>6 and XOS 2-6 ) for enzymatic hydrolysis (condition parameters are xylanase dosage of 1000 IU / kg, 50°C for 12 h) and purification (condition parameters are 10% activated carbon; microfiltration, 0.1 μm, 1-2 bar) to obtain xylose or XOS 2-6 .

[0057] (4) Delignification treatment: The washed solid pulp was delignified with KOH to obtain cellulose pulp under the conditions of 6 (w / w)% KOH, 100°C, 200 rpm, and 1 h.

[0058] (5) Low enzyme dosage enzymatic saccharification (low enzyme dosage hydrolysis): Cellulase was added to the cellulose pulp obtained in step (4) to make the cellulase activity in the cellulose pulp 3.5 FPU / g, the pH was controlled at 4.8, the enzymatic hydrolysis was carried out at 45°C for 16 h, the rotation speed was 200 rpm, and an enzymatic hydrolyzate was obtained.

[0059] (6) Feed liquid fermentation: dilute a portion of the enzymatic hydrolysate and mix it with (NH4)2SO4, KH2PO4, and MgSO4·7H2O to obtain an initial culture medium containing 40 g / L glucose, 2.2 g / L (NH4)2SO4, 2.0 g / L KH2PO4, and 1.0 g / L MgSO4·7H2O.

[0060] The initial culture medium was inoculated with Candida utilis for fermentation, with the inoculation amount being 5% of the culture medium volume, and the remaining enzymatic hydrolysate was fed at a rate of 10 L / min, and fermented at 30° C. for 12-24 hours until the dissolved oxygen content reached 80%, thereby completing the fermentation and obtaining a fermentation broth.

[0061] (7) Spray drying: The fermentation broth is centrifuged, autolyzed and broken, and spray dried in sequence to obtain a yeast protein-dietary fiber complex, wherein the centrifugation condition parameters are: 6000 rpm; the centrifuged concentrate is heated to 55°C and pH 5.8, and maintained for 6 hours to achieve yeast cell autolysis (autolysis and wall breaking), and then spray dried. The spray drying condition parameters are: inlet temperature 190°C, outlet temperature 85-95°C.

[0062] The components in the prepared yeast protein-dietary fiber complex were tested, and the test results are shown in Table 2.

[0063] Table 2 Detection results of corn cob yeast protein-dietary fiber complex components

[0064] As shown in Table 2, the crude protein content of the yeast protein-dietary fiber complex is 31%, the total dietary fiber is 45%, the aflatoxin is less than 2 μg / kg, and the zearalenone is less than 10 μg / kg.

[0065] Example 3

[0066] The difference from Example 1 is that the mass percentage concentration of sulfuric acid in the dilute sulfuric acid solution in step (1) is 0.16%, the temperature of the steam explosion treatment in step (2) is 188° C., the time is 3.6 min, the temperature of the water washing in step (3) is 60° C., the temperature of the delignification treatment in step (4) is 100° C., and the KOH concentration is 6 (w / w)%. However, the yeast protein-dietary fiber complex is finally produced with a low enzyme amount and the final nutritional value is equivalent to the parameters in Table 1.

[0067] Experimental Example 1 Evaluation of the standard terminal ileum amino acid digestibility of yeast protein-dietary fiber complex in pregnant sows

[0068] 1. Experimental Design: Thirty-two open-barreled sows (LY, parity 2) were surgically implanted with a T-tube in the terminal ileum. After recovery from surgery, the sows were synchronized for estrus and artificial insemination, and fed a standard commercial gestation diet from breeding until day 33 of gestation. A randomized block design was used. Sows were weighed at day 34 ± 2 of gestation and assigned to four groups based on body weight (195 ± 0.55 kg): a nitrogen-free diet (NF), a wheat straw yeast protein-dietary fiber complex (WSYP, prepared in Example 1), a corn cob yeast protein-dietary fiber complex (CCYP, prepared in Example 2), and a soybean meal (SBM) control. The nitrogen-free diet was used to assess endogenous protein and amino acid losses. Vitamin and mineral levels met or exceeded the NRC (2012) nutritional requirements for pregnant sows. All diets were supplemented with 0.4% chromium trioxide as an exogenous indicator. Diet formulations and nutrient levels are shown in Table 3.

[0069] Table 3 Diet composition and nutritional level (feeding basis, %) Note: The premix provides per kilogram of feed: copper sulfate 50 mg, ferrous sulfate 80 mg, potassium iodide 0.30 mg, manganese sulfate 20 mg, sodium selenite 0.2 mg, zinc sulfate 95 mg; the premix provides per kilogram of feed: VA 10,000 IU, VD3 1500 IU, VE 50 IU, VK3 4.4 mg, VB1 3.0 mg, VB2 6.0 mg, VB6 3.0 mg, VB12 0.04 mg, D-pantothenic acid 23 mg, niacin 36 mg, folic acid 0.8 mg, biotin 0.15 mg.

[0070] 2. Feeding Management and Sample Collection

[0071] Pregnant sows were housed in individual cages and fed twice daily at 08:00 and 15:30 (3 kg / day). The pens were cleaned after the second feeding each day to keep the environment clean and hygienic. The first five days of the experiment were a period of dietary adaptation. Ileal chyme was collected continuously for 12 hours from 08:00 to 20:00 on the sixth and seventh days of the experiment. A plastic bag was fixed to the fistula tube with a rubber ring. When the chyme in the plastic bag was full or exceeded 30 minutes, a new plastic bag was replaced. To prevent microbial degradation of amino acids in the ileal chyme, all collected chyme was immediately stored at -20°C. After the experiment, all collected chyme for each pig was slightly thawed and mixed evenly. 500 g of the chyme was freeze-dried and allowed to humidify at room temperature for 12 hours to prepare an air-dried sample. The sample was crushed to 60 mesh and stored at -20°C for testing.

[0072] 3. Test results:

[0073] The digestibility of protein and amino acids in chyme was investigated, and the results are shown in Table 4.

[0074] Table 4 Standardized ileal digestibility of protein and amino acids of yeast protein-dietary fiber complex in pregnant sows

[0075] According to the experimental results in Table 4, the wheat straw and corn cob yeast protein-dietary fiber complexes of the present invention have SIDs of 65.39% and 74.33% in pregnant sows, respectively, and have relatively high SIDs of amino acids (SIDAAs). Although the CP and SID of amino acids of the yeast protein-dietary fiber complex are significantly lower than those of soybean meal, it can still be used as a protein source in the production of breeding pig feed.

[0076] Example 4 Digestible Energy and Metabolizable Energy Evaluation Test of Dietary Fiber Bacterial Protein in Pregnant Sows

[0077] 1. Experimental Design: This study used a randomized block design. Twenty-four sows (LY, parities 3-4) at 38 ± 2 days of gestation were selected and weighed. Sows were then divided into four diets based on weight (221 ± 4.00 kg): a corn-based basal diet (BD), and experimental diets: wheat straw yeast protein-dietary fiber complex (WSYP, prepared in Example 1) and corn cob yeast protein-dietary fiber complex (CCYP, prepared in Example 2). The latter replaced 33.4% and 34.3% of the corn in the basal diet, respectively. Digestible and metabolizable energy (DE) were determined using the total fecal and urine collection method. Finally, the DE and ME of the raw materials were calculated using a nested algorithm. The diet formula is shown in Table 5. Vitamin and mineral levels met or exceeded the NRC (2012) nutritional requirements for pregnant sows.

[0078] Table 5 Diet composition and nutritional level (feeding basis, %) Note: The premix provides per kilogram of feed: copper sulfate 50 mg, ferrous sulfate 80 mg, potassium iodide 0.30 mg, manganese sulfate 20 mg, sodium selenite 0.2 mg, zinc sulfate 95 mg; the premix provides per kilogram of feed: VA 10,000 IU, VD3 1500 IU, VE 50 IU, VK3 4.4 mg, VB1 3.0 mg, VB2 6.0 mg, VB6 3.0 mg, VB12 0.04 mg, D-pantothenic acid 23 mg, niacin 36 mg, folic acid 0.8 mg, biotin 0.15 mg.

[0079] 2. Experimental Management and Sample Collection: One week prior to the start of the experiment, selected pigs were transferred to metabolic cages. During the acclimation period, they were fed a standard commercial gestating sow diet. During the experimental period, equal amounts of feed (3 kg / day) were provided twice daily at 8:00 AM and 3:30 PM, with free access to water. Feed waste was accurately recorded for each pig during the experimental period. The pig house temperature was maintained at 22-25°C, and the pig house was cleaned daily after feeding in the afternoon to ensure cleanliness and hygiene.

[0080] The sample collection adopts the full fecal collection method. The 6 days before the experiment are the adaptation period. Before the feeding starts at 8:00 am on the 7th day, 2% ferric oxide is added to the feed of each sow as an indicator for feces collection. Continuous feces collection begins when the test pigs excrete red feces. At 8:00 am on the 12th day, 2% ferric oxide is also added to the feed of each pig. When the test pigs have red feces, collection is stopped. The feces collected every day during the experiment are stored at -20℃. After the feces are collected, all the feces are weighed and mixed evenly. 1 / 4 of the weight of the feces is taken, and 6 mol / LHCL is added to fix nitrogen at 5% (w / v). It is dried in a 55℃ oven for 72 hours to constant weight and then rehydrated for 24 hours. The sample is then crushed and passed through a 60-mesh sieve and stored at -20℃ for testing.

[0081] Urine samples were collected from 08:00 on the 7th day to 08:00 on the 12th day. A urine collection basin was placed below the metabolic cage and emptied at least twice daily. Each time the urine basin was emptied, 50 mL of 6 mol / L hydrochloric acid was added. A 10% sample of the collected urine was taken and stored at -20°C. After the experiment, all urine samples were thawed, mixed, brought to volume, and weighed. The samples were then filtered through filter paper into 50 mL centrifuge tubes and stored at -20°C until testing.

[0082] 3. Test results:

[0083] The results of the investigation on energy digestion and metabolism parameters of the experimental diet in pregnant sows are shown in Table 6, and the effects on digestible energy, dry matter and nutrient digestibility in pregnant sows are shown in Table 7.

[0084] Table 6 Energy digestion and metabolism parameters of experimental diets in pregnant sows Note: Lowercase letters indicate significant differences at the 0.05 level. The same letters in the same column indicate that the differences do not reach the significant level. The same applies to the following tables.

[0085] Table 7 Digestible energy, dry matter and nutrient digestibility of yeast protein-dietary fiber complex in pregnant sows

[0086] The experimental results recorded in Tables 6 and 7 show that the digestible energy and metabolizable energy of the wheat straw and corn cob yeast protein-dietary fiber complexes of the present invention in pregnant sows were 16.93 MJ / kg and 17.11 MJ / kg, and 16.39 MJ / kg and 16.67 MJ / kg, respectively, which were slightly lower than soybean meal. At the same time, the fecal moisture content and dry matter-based fecal excretion of the wheat straw and corn cob yeast protein-dietary fiber complexes were significantly higher than those of soybean meal. This fully demonstrates that the yeast protein-dietary fiber complex of the present invention can serve as an energy feed raw material while also having high-quality fiber properties, which is beneficial to defecation in sows and can effectively alleviate their constipation problems.

[0087] Example 5 Effect of Yeast Protein-Dietary Fiber Complex Replacing Fish Meal on Growth Performance of Weaned Piglets

[0088] 1. Experimental Design: A single-factor randomized design was used. Seventy-two weaned piglets, weighing approximately 7 kg, were selected and randomly assigned to three treatment groups, each with eight replicates. Each replicate consisted of three pigs (two boars and one sow). The experimental period was 21 days. The specific experimental design and diet were discussed.

[0089] Table 8 Diet composition and nutritional level (feeding basis, %)

[0090] 2. Test results

[0091] The effects of different treatments on the growth performance of weaned piglets are shown in Table 9.

[0092] Table 9 Effects of yeast protein-dietary fiber complex replacing fish meal on growth performance of weaned piglets

[0093] The experimental results in Table 9 show that the diarrhea index in the 3% yeast protein group was significantly higher than that in the control group. However, compared with the control group, the other treatment groups (3% yeast protein group and 6% yeast protein group) showed no differences in body weight, feed intake, daily gain, and feed-to-meat ratio at each stage and throughout the entire feeding period. In summary, the yeast protein-dietary fiber complex at 3% and 6% addition levels is feasible for full or partial replacement of fish meal and can be used as a dietary protein source in weaned piglets.

[0094] Example 6 Comparison of the Effects of Yeast Protein-Dietary Fiber Complex and Similar Product Angel Yeast Protein Substituting Fish Meal on the Reproductive Performance of Sows During the Peripartum and Lactation Period (Comparison of Similar Products)

[0095] 1. This study adopted a completely randomized block design, with sows entering the farrowing house on the same day of gestation (107 days) and the same batch as the other blocks. 150 LY sows with similar parity and backfat were selected and assigned to three treatment groups (control group (CON) and two treatment groups (T1 and T2)) on day 107 of gestation according to backfat, body weight, and parity, with 50 replicates per group and one sow per replicate. The experimental period was from day 107 of gestation to day 18 of lactation. The experimental treatments were as follows: (1) CON was the basal diet—the nutritional level was based on the nutritional requirements of pregnant sows as defined by the NRC (2012); (2) T1 was supplemented with yeast protein-dietary fiber complex (CP, 30%, CCYP, prepared in Example 2) to replace 7% of the basal diet with CP; (3) T2 (positive control) was supplemented with 2.6% Angel Yeast Yeast Protein (AQYP). The specific component contents are shown in Table 10.

[0096] Table 10 Diet composition and nutritional levels of different treatments

[0097] 2. Feeding Management and Sample Collection

[0098] This experiment was conducted in a commercial pig farm in Suining, Sichuan Province. (1) From gestation day 107 to farrowing day 18 (approximately 25 days), sow feeding amount: 3 kg / day in late gestation, no feed on farrowing day, 2 kg on the first day after farrowing, and 1.0 kg daily thereafter. On the fifth day, sows were free to eat and drink; (2) Cross-fostering: Cross-fostering was completed 24 hours after farrowing. Based on the mammary development of the sows, each sow was guaranteed to have 13-14 piglets, so that the piglets could eat colostrum as soon as possible. (3) Environmental control: The temperature of the farrowing house was controlled at 20-22°C. If it exceeded this range, insulation or heat dissipation measures should be taken. Clean and disinfect the pig pens regularly according to the routine cleaning and disinfection system of the pig farm, and ensure air circulation in the house; (4) Piglet management: weighing at birth, ear marking, tail docking, tooth cutting, castration and other procedures are carried out according to the routine procedures of the pig farm; sow reproductive performance: total number of piglets born, number of live piglets, number of stillbirths, piglet birth weight, weaning litter weight, number of weaned piglets; sow feed intake: record the sow's daily feed intake and residual amount, and calculate the average feed intake during lactation; back fat changes: record the sow's back fat at 106 days of gestation, 24 hours after delivery, and 18 days of lactation; piglet production Results: The birth weight and weaning weight of piglets on days 7, 14, and 18 were measured. The piglet production, litter weight, average weight, litter weight gain, and average weight gain of piglets were calculated. The number of piglets at each stage was recorded. The sow constipation index, fecal endotoxin content, and plasma IgM and IL10 concentrations were also investigated. Plasma IgM and IL10 concentrations were assessed using ELISA kits (manufacturer: Ruixin, IL-10 product number RX501078P, IgM product number RX500977P). The results are shown in Tables 11-13 and Figures 2-4.

[0099] Table 11 Reproductive performance of sows

[0100] Table 12 Sow production performance during lactation

[0101] Table 13 Milk composition at different stages of lactation

[0102] According to the experimental results recorded in Tables 11, 12, 13, Figures 2, 3 and 4, the yeast protein-dietary fiber complex significantly improved the birth uniformity of piglets compared with the control group and the similar product Angel Yeast group (P=0.01); the yeast protein-dietary fiber complex replacing the fish meal protein in the lactating sow formula had no significant effect on the litter weight gain, daily weight gain, sow feed intake, milk production (Figure 2 and Table 12) and milk composition of lactating piglets (P>0.05). However, the yeast protein-dietary fiber complex significantly improved the constipation index of sows during the peripartum period, reduced the endotoxin content in feces (Figure 3) (P<0.05), and significantly improved the immune and inflammatory status of sows during the peripartum period (Figure 4) (P<0.05). In summary, the yeast protein-dietary fiber complex developed by the present invention can completely replace 2% fish meal and 5% wheat bran in the formula at a 4% addition amount; the yeast protein-dietary fiber complex described in the present invention can be used as a protein source and dietary fiber source for sows, replacing 7% protein and 12% total dietary fiber in the formula. At the same time, this product can also be used as a dietary fiber source for pregnant and lactating sows, significantly improving the constipation, immune and inflammatory status of sows during the peripartum and lactation periods, and is beneficial to the postpartum recovery of sows and the growth of piglets. It is superior to similar Angel yeast protein products.

[0103] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a yeast protein-dietary fiber complex, characterized in that, It includes the following steps: After the biomass raw material is pretreated, it is successively subjected to steam explosion treatment, water washing treatment, delignification treatment, low-enzyme dosage enzymatic hydrolysis, fed-batch liquid fermentation and spray drying treatment to obtain a yeast protein-dietary fiber complex; The enzyme used in the low-enzyme dosage enzymatic hydrolysis is cellulase; the dosage of the cellulase is 1.5 FPU / g - 3.5 FPU / g.

2. The preparation method according to claim 1, characterized in that, The pH value of the low-enzyme dosage enzymatic hydrolysis is 4.8 - 5.8, the time is 16 - 72 h, and the temperature is 45 - 55 °C.

3. The preparation method according to claim 1, characterized in that, The fed-batch liquid fermentation includes: diluting a part of the enzymatic hydrolysate obtained by low-enzyme dosage enzymatic hydrolysis and saccharification, and mixing it with (NH4)2SO4, KH2PO4 and MgSO4·7H2O to prepare an initial medium; The concentration of glucose in the initial medium is 40 g / L, the concentration of (NH4)2SO4 is 2.2 g / L, the concentration of KH2PO4 is 2.0 g / L, and the concentration of MgSO4·7H2O is 1.0 g / L; Candida utilis is inoculated into the initial medium for fermentation culture, and the remaining enzymatic hydrolysate obtained by low-enzyme dosage enzymatic hydrolysis and saccharification is fed into the initial medium at a rate of 10 - 30 L / min.

4. The preparation method according to claim 3, characterized in that, At the time of inoculation, the inoculation amount is 5% of the volume of the initial medium; The temperature of the fed-batch liquid fermentation is 30 - 35 °C; the end criterion of the fed-batch liquid fermentation is that the dissolved oxygen degree of the fermentation broth obtained by fermentation reaches 80 - 90%.

5. The preparation method according to claim 1, characterized in that, The temperature of the steam explosion treatment is 180 - 212 °C, and the pressure maintaining time is 3 - 5 min; The temperature of the water washing treatment is 60 - 100 °C, the rotation speed is 200 rmp, and the time is 1 h. The mass percentage content of KOH in the KOH solution used in the delignification treatment is 6 - 10%; the temperature of the delignification treatment is 100 °C, and the rotation speed is 200 rpm.

6. The preparation method according to claim 1, wherein Before the spray drying treatment, it also includes centrifuging the fermentation broth obtained by fed-batch liquid fermentation.

7. The preparation method according to claim 1, wherein The pretreatment includes the steps of crushing the biomass raw material, mixing and soaking it with an acid solution, and then centrifuging; The biomass raw material includes one or more of wheat straw, rice straw, corn straw, corn cob and bagasse.

8. A yeast protein-dietary fiber complex prepared by using the method according to any one of claims 1 - 7.

9. Use of the yeast protein-dietary fiber complex according to claim 8 in the preparation of a feed having the effect of improving constipation in sows and / or reducing diarrhea in weaned piglets.

10. A feed rich in protein and dietary fiber, characterized in that, The active ingredient includes the yeast protein-dietary fiber complex according to claim 8.

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