Production method for deep processing of defatted rice bran for feed

Abstract

The invention provides a deep processing production method of defatted rice bran for feed. According to the method, lactic acid bacteria and saccharomycetes are used for fermentation treatment to obtain defatted rice bran with high crude protein content. According to the method, the pH value of the defatted rice bran is reduced through limited growth of lactic acid bacteria on a defatted rice bran culture medium, and the optimal enzymolysis pH range of xylanase is achieved while infectious microbe pollution is prevented. Under the action of xylanase, part of crude fibers in the defatted rice bran are degraded into xylooligosaccharide, xylose and other micromolecular sugars; then yeast capable of assimilating xylose is used for fermentation, carbohydrates formed by degrading the crude fibers are converted into mycoprotein, and therefore the crude protein content of the defatted rice bran for the feed is increased. The texture and taste of the fermented defatted rice bran are obviously improved, the content of crude protein is increased, a large number of beneficial microorganisms and metabolites thereof are introduced, a novel biological protein feed raw material product is formed, soybean meal in the breeding industry is effectively and partially replaced, and a high-quality protein feed resource is formed.

Description

Technical Field

[0001] The invention belongs to the technical field of microbial fermentation, and in particular relates to a production method for improving the crude protein content of defatted rice bran for feeding. Background Art

[0002] With the rapid economic development and the improvement of people's living standards in my country, the demand for animal foods such as meat, eggs, and milk has increased dramatically in the past 20 years, which has promoted the rapid development of animal husbandry, and the demand for energy feed raw materials and protein feed raw materials has increased accordingly. Due to the strong dependence of the feed industry on grain resources, a situation of "people and animals competing for food" has been created. Soybean meal is the main source of protein feed raw materials. my country consumes a huge amount of soybean meal every year, but due to limited domestic land resources and low level of large-scale bean planting, the output of soybeans is in short supply, resulting in domestic soybean meal being extremely dependent on imports, and the foreign dependence of soybeans exceeds 80%. The main risks of relying on imports are large volume, high foreign dependence, and concentrated sources. In particular, the current geopolitical risks, extreme climate disasters, poor supply chain and other unfavorable factors are intertwined and superimposed, which will continue to bring operating pressure to the feed industry and downstream breeding industry, seriously affecting the domestic soybean planting industry chain and endangering my country's food security. The shortage of protein feed raw materials has become one of the bottlenecks restricting the sustainable development of livestock and poultry farming.

[0003] Rice bran is a byproduct of rice processing. It is extremely rich in rice-producing areas in my country, especially in the southern part of the country, with an annual output of more than 10 million tons. At present, most rice bran is defatted to extract rice bran oil, which has good economic benefits. Defatted rice bran, also known as rice bran meal, is a low-energy, high-fiber raw material. The high content of crude fiber, mainly non-starch polysaccharides (NSP) such as pentosan and glucan, is the primary anti-nutritional factor as a feed raw material. Large amounts of feeding can cause constipation in animals (the result of large amounts of water adsorbed by crude fiber). Defatted rice bran is a low-energy raw material compared to corn as a feed raw material. Although the protein quality is not bad, it is only about 15%, which is a big gap compared to the protein raw materials recognized by the industry (at least 20% protein content). The research results of Huang et al. (2018) show that the effective energy of defatted rice bran is highly negatively correlated with the fiber content. Unlike glucose, xylose produced by enzymatic hydrolysis of pentosan (xylan) is not easily utilized by monogastric animals. Even if one hopes to eliminate the adverse effects of crude fiber by adding non-starch polysaccharide enzymes to the diet, it cannot change its low-energy and low-protein characteristics.

[0004] Patent document CN108850549A discloses a multi-strain fermentation process of defatted rice bran, which uses a composite strain composed of Trichoderma koningii, Geotrichum candidum, and Streptococcus thermophilus for mixed fermentation treatment, which reduces the crude fiber level in defatted rice bran and increases the polysaccharide content. However, these strains cannot further ferment and convert the polysaccharides generated by crude fiber degradation into proteins during fermentation, resulting in a low protein level in the defatted rice bran raw material, a low utilization rate, and the liquid fermentation method is extremely costly and has extremely low fermentation efficiency.

[0005] Therefore, if the defatted rice bran can be processed deeply at a lower cost in production, part of the crude fiber can be converted into bacterial protein, thereby increasing the crude protein content of the defatted rice bran, then the processed defatted rice bran can partially replace soybean meal, solving the contradiction between the shortage of soybean meal resources and the sharp increase in demand in my country, and will achieve good economic, social and ecological benefits. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a deep processing technology for defatted rice bran for feed, which does not subject the defatted rice bran to high-temperature sterilization, but utilizes the combined effects of enzymatic hydrolysis and microbial fermentation to reduce the crude fiber of the defatted rice bran and converts part of the crude fiber into bacterial protein to increase the protein content of the defatted rice bran.

[0007] On the one hand, the present invention provides a production method for increasing the crude protein content of defatted rice bran for feed, wherein the method does not require high-temperature sterilization of the fermentation medium, but directly pre-treats it with lactic acid bacteria and then ferments it with yeast.

[0008] In the prior art, generally composite strains or bacterial enzyme combined fermentation methods are used to reduce the crude fiber level of defatted rice bran through solid fermentation or liquid fermentation processes, thereby increasing the sugar content or protein content. As a feed raw material, rather than a feed additive, liquid fermentation processes are generally not used because liquid fermentation requires high temperature sterilization, sterile air is introduced in large quantities during cultivation, and the solid content is low, resulting in low fermentation efficiency and extremely high cost. Therefore, the present invention considers a single enzyme preparation that can utilize the xylose generated by the degradation of crude fiber xylan in defatted rice bran, and further assimilates xylose to generate bacterial protein through the process of solid fermentation.

[0009] There are many microorganisms in nature that can utilize xylose, such as Bacillus, yeast, and Lactobacillus. However, since the protein content of Bacillus itself is not high, the starch and protein in the culture medium are first utilized during growth, and a neutral or alkaline culture medium is required during the fermentation process; and Lactobacillus has a low efficiency in assimilating xylose under solid conditions. Since yeast does not utilize protein and starch in the culture medium, the present invention compares the ability of different types of yeast species to assimilate xylose to produce crude protein. The results showed that the efficiency of xylose utilization by Saccharomyces cerevisiae and Saccharomyces boulardii was low, and there was no significant difference between them and the control; the ability of Candida utilis, Candida tropicalis, and Wickham's abnormal yeast to utilize xylose was different from that of Kluyveromyces marxianus, so the present invention preferably uses Kluyveromyces marxianus.

[0010] In addition, the pH value of the substrate during the fermentation process will have a greater impact on the activity of the enzyme and the growth of microorganisms. Therefore, it is necessary to adopt corresponding pH value adjustment and control methods during the fermentation process. In the liquid fermentation process, the pH of the fermentation environment is usually controlled by adjusting the initial pH value of the culture medium, adding acid or alkali during the fermentation process to adjust the pH, or adjusting the pH value by feeding. However, the production cost of liquid fermentation is high, and it is generally used to produce high-value feed additives. Therefore, the present invention utilizes a solid fermentation method that can produce feed raw materials, and the equipment is simple and easy to operate. However, in the solid fermentation process, it is difficult to achieve the same as liquid fermentation, and the pH is adjusted during the fermentation process. Therefore, the present invention considers adjusting the pH environment of the fermentation substrate before the start of fermentation, and compares the method of adding dilute strong acid and the selection of strains that can produce acid during fermentation. It is found that the method of directly adding acid to control the pH of the fermentation substrate during the fermentation process is not the best choice for increasing crude protein, and by contrast, lactic acid bacteria co-culture to adjust acidity to increase crude protein is better. When lactic acid bacteria and xylanase are used for co-fermentation, since defatted rice bran is not a suitable culture medium for lactic acid bacteria, lactic acid bacteria grow limitedly in the defatted rice bran matrix. As the acid production of lactic acid bacteria increases, the pH of defatted rice bran is adjusted from neutral to slightly acidic, with a pH between 4.0 and 5.0. In this slightly acidic culture medium, bacteria and other bacteria in the air are not easy to grow, and the optimal enzymatic hydrolysis range of xylanase is also reached. Xylanase enzymatically hydrolyzes hemicellulose in plant cell walls to generate small molecular sugars such as oligoxylose and xylose, which significantly reduces the crude fiber level in defatted rice bran. The environmental conditions suitable for yeast growth are also slightly acidic. Yeast that can assimilate xylose is further added for mixed fermentation. Sugar substances such as oligoxylose or xylose formed by the degradation of xylan are converted into bacterial protein by yeast assimilation together with the added inorganic nitrogen substances, thereby increasing the crude protein content of defatted rice bran for feeding.

[0011] Furthermore, the lactic acid bacteria include one or more of Lactobacillus plantarum, Lactobacillus acidophilus, and Lactobacillus casei.

[0012] The effect of lactic acid bacteria in feed fermentation can not only regulate the pH range of suitable enzymolysis, promote the decomposition of the fiber material xylan in defatted rice bran, but also resist the pollution of exogenous bacteria. For raw materials that have not been sterilized at high temperature, it is particularly important to prevent bacterial contamination, which is conducive to the smooth progress of the fermentation process. In addition, lactic acid bacteria present in the product also help to regulate the balance of animal intestinal flora. The lactic acid bacteria generally used for feed fermentation have lactobacillus, bulgaricus lactobacillus, plant lactobacillus, acidophilus lactobacillus, casei lactobacillus, etc. The present invention verifies the influence of the protein content in defatted rice bran during the combined fermentation of several lactobacillus and Kluyveromyces marxianus by screening experiments, and it is found that casei lactobacillus shows suitable acid production ability and antioxidant properties, while other lactobacillus such as acidophilus lactobacillus and casei lactobacillus are strictly anaerobic, poorly grown, and poorly acid-producing, so casei lactobacillus is preferred.

[0013] Furthermore, the lactic acid bacteria include Lactobacillus casei.

[0014] In some embodiments, the present invention uses Lactobacillus casei powder for fermentation. Since commercial Lactobacillus casei agents are extremely abundant on the market, the use of commercial powder is cheap and convenient, and does not require complicated pre-production preparations, which greatly simplifies the fermentation production process.

[0015] Furthermore, the yeast includes one or more of Kluyveromyces marxianus, Candida utilis, Candida tropicalis, and Anomalisa wickhamii.

[0016] Xylose is a pentose that is difficult for monogastric animals to absorb and utilize. Some yeasts in nature can utilize xylose, but most yeasts have poor ability to utilize xylose. There are not many yeast species that can efficiently utilize xylose, the enzymatic hydrolysis product of xylan, to convert it into their own protein, including Kluyveromyces marxianus and Candida utilis. Among them, Kluyveromyces marxianus is a commonly used microecological preparation strain, which can grow well in the temperature range of 30-40℃. In addition to yeast cells and extracellular metabolites, the fermentation culture of this bacteria also contains autolysis products such as peptides, organic acids, oligosaccharides, amino acids, flavor enhancers and aromatic substances. The ability of six yeasts, including Kluyveromyces marxianus, Candida utilis, Candida tropicalis and Wickham's abnormal yeast, to convert xylose into protein was verified through experiments. The results showed that Kluyveromyces marxianus had the highest efficiency in assimilating xylose to generate bacterial protein, so Kluyveromyces marxianus was finally selected.

[0017] Furthermore, the yeast includes Kluyveromyces marxianus.

[0018] Furthermore, the method comprises the following steps:

[0019] (1) Preparation of Kluyveromyces marxianus liquid seeds;

[0020] (2) bacterial enzyme combined pretreatment of defatted rice bran;

[0021] (3) Fermentation treatment of Kluyveromyces marxianus.

[0022] Furthermore, the temperature of the heat preservation fermentation of the bacterial enzyme combined pretreatment in step (2) is 35-37°C.

[0023] Temperature affects the acid production of lactic acid bacteria and also affects the decomposition of enzymes. The most suitable growth temperature for Lactobacillus casei is between 30 and 35°C, and it will no longer grow above 40°C; at the same time, the most suitable temperature for enzymatic hydrolysis of xylan is between 40 and 50°C, and the maximum cannot exceed 60°C. Therefore, the selection of the initial temperature must meet or be close to the optimal action range of the enzyme and meet the growth temperature range of lactic acid bacteria. Defatted rice bran is not the most suitable culture medium for lactic acid bacteria, and its growth rate is slower than that of conventional culture medium for lactic acid bacteria. The growth degree of lactic acid bacteria can be adjusted by adjusting the initial culture time, so as to achieve a suitable pH environment for xylanase to work.

[0024] On the other hand, the present invention provides a use of lactic acid bacteria for preparing an agent for reducing the pH value of defatted rice bran, characterized in that the lactic acid bacteria include one or more of Lactobacillus plantarum, Lactobacillus acidophilus, and Lactobacillus casei.

[0025] Furthermore, the lactic acid bacteria include Lactobacillus casei.

[0026] In another aspect, the present invention provides a use of yeast for preparing an agent for increasing the protein content of defatted rice bran, wherein the yeast comprises one or more of Kluyveromyces marxianus, Candida utilis, Candida tropicalis, and Anomalisa wickhamii.

[0027] Furthermore, the yeast includes Kluyveromyces marxianus.

[0028] The present invention has the following beneficial effects:

[0029] 1. The limited growth of Lactobacillus casei in defatted rice bran culture medium is used to adjust the pH of the defatted rice bran matrix from neutral to slightly acidic, which helps to resist the contamination of foreign bacteria during fermentation and provides the best pH range for xylanase to hydrolyze xylan.

[0030] 2. Inoculate Kluyveromyces marxianus, which can utilize xylose, to effectively convert the decomposition products such as xylose and other pentose into yeast body protein, reduce the crude fiber content in defatted rice bran, and increase the crude protein content in defatted rice bran;

[0031] 3. The inoculated microorganisms Lactobacillus casei and Kluyveromyces marxianus do not utilize or damage the starch and protein in the defatted rice bran itself, effectively retaining the high-quality starch and protein in it. The increase in protein is a bacterial protein synthesized by exogenous inorganic nitrogen and xylooligosaccharides and xylose produced by xylanase hydrolysis, which cannot be utilized by monogastric animals.

[0032] 4. The texture and taste of defatted rice bran after fermentation are significantly improved, which not only increases the crude protein content, but also introduces a large number of beneficial microorganisms and their metabolites, forming a new type of bio-protein feed raw material product. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with the examples. It should be noted that the examples described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on it. The reagents used in this example are all known products and were obtained by purchasing commercially available products.

[0034] Embodiment 1, the production method of defatted rice bran for feeding provided by the present invention

[0035] (1) Preparation of Kluyveromyces marxianus liquid seeds:

[0036] The original slant strain of Kluyveromyces marxianus (strain collection number CICC 1218) was inoculated into a 250 mL seed medium of a flask, and was statically cultured at 30-32° C. for 30-36 hours to obtain flask seeds; one seed in the flask was inoculated per 100 L of fermentation seed liquid in the seed tank, and the slant seeds of the flask were washed into the seed tank, and were cultured at 30-32° C., 160-180 rpm, and a ventilation volume of 1:0.5-0.6 (V / V) for 16-18 hours to obtain fermentation seed liquid for standby use.

[0037] The above-mentioned eggplant flask seed culture medium formula is:

[0038] Peptone 10g / L, yeast extract powder 10g / L, potassium dihydrogen phosphate 5g / L, glucose 20g / L, agar powder 18g / L, prepared by sterilization at 121℃ for 15min;

[0039] The culture medium formula of the fermented seed liquid in the above seed tank is:

[0040] It is prepared by 10g / L peptone, 10g / L yeast extract powder, 5g / L potassium dihydrogen phosphate, and 20g / L glucose, sterilized at 118℃ for 15min;

[0041] (2) Bacterial and enzyme combined pretreatment of defatted rice bran

[0042] Defatted rice bran and water are in a weight ratio of 100:85, and Lactobacillus casei powder (feed additive grade, viable count 100 billion / g, purchased from the market), ammonium sulfate (chemical grade, purity greater than 98%, purchased from the market), and xylanase (feed additive grade, 2000U / g, purchased from the market) are added in proportion. The temperature of the mixing water is maintained between 35 and 40° C. After uniform mixing, the mixture is added to an insulated storage tank. Under the insulated condition of 35 to 37° C., the mixture is insulated for 18 hours. 50g of commercial lactic acid bacteria powder, 2.5Kg of ammonium sulfate, and 100g of xylanase are added to every 100Kg of defatted rice bran.

[0043] (3) Fermentation of Kluyveromyces marxianus

[0044] The fermentation liquid of Kluyveromyces marxianus is added to the material treated in step (2) at an amount of 5% of the weight before the defatted rice bran treatment, mixed evenly, and kept warm. The temperature of the mixture is maintained at 33-35° C., and a chain-type automatic turning device is used to carry out yeast solid fermentation. After keeping warm for 30-36 hours, the culture is terminated. After the culture is completed, the defatted rice bran fermentation product is dried, and then the crude protein and crude fiber content in the defatted rice bran fermentation product is determined.

[0045] Example 2: Screening of strains for converting xylan hydrolysis products into yeast protein

[0046] In nature, some microorganisms can effectively utilize the xylose, a product of the enzymatic hydrolysis of xylan, to convert it into its own bacterial protein, thereby increasing the protein content in the feed. Different strains have different utilization and assimilation efficiencies for xylose. Under the same amount of defatted rice bran, the higher the protein content, the higher the conversion efficiency of the strain to synthesize bacterial protein by assimilating xylose. Since Bacillus is not suitable for growth in a slanting acidic environment, and at the same time, defatted rice bran lacks the organic small molecule nitrogen source necessary for the large-scale growth of lactic acid bacteria and is not suitable for growth, this embodiment further explores the ability of different types of yeast to utilize the enzymatic hydrolysis products of xylanase to convert and generate bacterial protein, and screens for fermentation strains with higher conversion efficiency. This embodiment provides 6 types of yeast strains shown in Table 1 for later fermentation, and the remaining processes and steps are the same as in Example 1. The control is not inoculated with yeast, and the crude fiber content is determined by the dry pot method, and the crude protein content is calculated by the Kjeldahl method. The determination results are shown in the following table.

[0047] Table 1 Determination of substance content in defatted rice bran fermentation products under different yeast conditions

[0048]

[0049]

[0050] According to the data in Table 1, it can be seen that when only lactic acid bacteria are added to the fermentation matrix (control), the content of crude protein converted from crude fiber is low; adding yeast species that can utilize xylose to defatted rice bran can increase the crude protein content in defatted rice bran, but due to the low efficiency of xylose utilization by Saccharomyces cerevisiae and Saccharomyces boulardii, there is no significant difference between the crude protein content increased by these two yeasts and the control.

[0051] At the same time, by comparing groups 3 to 6 with the control, it can be seen that the four yeasts can significantly increase the content of crude fiber converted into crude protein. When fermented with Kluyveromyces marxianus, the crude protein content was 23.29% and the crude fiber content was 8.8%; when fermented with Candida utilis, Candida tropicalis, and Wickham's abnormal yeast, the crude protein content was 20.75%, 20.76%, and 20.38%, respectively. It can be seen that the conversion efficiency of the bacterial protein of Kluyveromyces marxianus is the highest, and there is a difference between the conversion ability of the other three yeasts and Kluyveromyces marxianus, because the bacterial protein content of Kluyveromyces marxianus itself is high and the efficiency of converting xylose into its own bacterial protein is also high. Therefore, Kluyveromyces marxianus is preferred in this embodiment.

[0052] Example 3: Screening of pH adjustment methods

[0053] In the actual fermentation process, pH value is a crucial parameter, which directly affects the growth and metabolism of microorganisms. For example, the optimum pH range for the growth of Kluyveromyces marxianus is between 4.0 and 6.0. At the same time, enzymes are biologically active substances, and their efficiency and activity are also significantly affected by pH value, and the optimum pH range of xylanase is between 4.0 and 6.0. Since the pH adjustment method of solid fermentation process is not as convenient as liquid fermentation, this embodiment considers adjusting the pH environment of defatted rice bran by adding cheap inorganic acid or adding microorganisms before fermentation begins. The pH adjustment method is shown in Table 2, and the remaining processes and steps are the same as in Example 1, and the control is not to adjust the pH. Crude fiber and crude protein content are shown in Table 2.

[0054] Table 2 Effects of different pH adjustment methods on crude fiber conversion to crude protein

[0055]

[0056]

[0057] As can be seen from the results in Table 2, when the pH of the fermentation substrate is not adjusted (control), the content of crude protein converted from crude fiber is low. The reason is that the rice bran substrate is neutral and alkaline, which is not conducive to the action of xylanase and is not suitable for the growth of Kluyveromyces marxianus. Compared with the control, after a certain adjustment method is adopted to change the pH of the fermentation environment, it is conducive to the decomposition of xylanase and can increase the crude protein content in defatted rice bran. Compared with the method of directly adding dilute sulfuric acid, the method of adjusting the fermentation of lactic acid bacteria powder can further increase the content of crude protein and reduce the crude fiber level. The reason is that the limited growth of lactic acid bacteria can contribute a certain amount of bacterial protein on the one hand, and on the other hand, the oligosaccharides in the enzymolysis products that yeast cannot assimilate are used to help reduce the fiber content.

[0058] Example 4: Screening of different lactic acid bacteria

[0059] During the feed fermentation process, lactic acid bacteria will produce a large amount of acid during fermentation, which will quickly reduce the pH of the fermentation medium system, inhibit the activities of other bacteria, and prevent and control contamination by miscellaneous bacteria; at the same time, it will provide a suitable acidic enzymolysis environment for the enzymolysis of xylanase. However, different strains of lactic acid bacteria have different acid production abilities and different growth conditions. In order to screen lactic acid bacteria with appropriate acid production, this embodiment provides three kinds of commercial lactic acid bacteria powders shown in Table 3 for the production of defatted rice bran. The remaining processes and steps are the same as those in Example 1, and the control is that lactic acid bacteria powder is not added. The measurement results are shown in Table 3.

[0060] Table 3 Acid production efficiency of different strains and determination of substance content in defatted rice bran

[0061]

[0062] According to Table 3 results, compared with Lactobacillus casei, when Lactobacillus plantarum and Lactobacillus acidophilus are utilized to carry out fermentation treatment, the crude protein content level generated is low, the reason is that Lactobacillus plantarum and Lactobacillus acidophilus need strict anaerobic, and growth conditions are harsh, and defatted rice bran is not its suitable growth medium, lactic acid bacteria thalline self growth and reproduction is bad, and the acid production effect is poor during the production time used by the technique provided by the present invention, and the ability of xylanase to utilize crude fibers such as xylan to be converted into xylose is reduced, and the xylose generated is reduced, further causing the raw material that yeast in the later stage can utilize to reduce, and the crude protein content generated is reduced. And when Lactobacillus casei is adopted to carry out fermentation treatment, because Lactobacillus casei is facultative anaerobic bacteria, and growth conditions require compared with Lactobacillus plantarum and Lactobacillus acidophilus, relatively not high, relatively can be better grown on defatted rice bran, the protein content in the fermentation product is 23.42%, and crude fiber content is reduced to 8.8%, compared with other two kinds of lactobacilli and contrast, crude fiber content significantly reduces, and crude protein content significantly improves. Therefore, the preferred Lactobacillus casei of the present embodiment.

[0063] Example 5: Screening of insulation temperature during combined pretreatment with lactic acid bacteria and xylanase

[0064] Temperature is one of the important factors that affect the pH value change during the fermentation process. The fermentation temperature of lactic acid bacteria and xylanase in the early stage mainly acts on the pH value indirectly by affecting the activity of xylanase and the growth rate of lactic acid bacteria. Therefore, the selection of the early stage temperature must meet the optimal action range of xylanase and reach the growth range of lactic acid bacteria. In order to further screen the fermentation temperature that meets the limited growth of lactic acid bacteria and the optimal environment for enzymolysis simultaneously, the present embodiment provides several different fermentation temperatures of heat-insulating storage tanks, as shown in Table 4, and the remaining processes and steps are the same as in Example 1, and the comparison is not to do temperature treatment. The measurement results are shown in the table below.

[0065] Table 4 Effects of different temperatures on lactic acid bacteria growth and xylanase activity

[0066]

[0067] As shown in Table 4, crude protein and crude fiber have undergone significant changes in the gradual increase of temperature. Among them, the growth rate of lactic acid bacteria gradually accelerates with the increase of temperature, reaching a maximum value at 35°C, and if the temperature is increased again on the basis of 35°C, the growth rate of lactic acid bacteria decreases instead, and at 40°C, it does not grow basically, and the pH regulating effect disappears. But in terms of temperature, the enzyme activity of xylanase under low temperature (room temperature, 30°C) and higher temperature (35°C) conditions will be significantly lower than the enzyme activity under 40~45°C conditions, which is determined by the characteristics of xylanase. Although the lower temperature of 30~35°C is suitable for lactic acid bacteria growth, it is not suitable for the most suitable action temperature of xylanase (40~50°C). Therefore, the preferred early fermentation temperature of lactic acid bacteria in this embodiment is 35~37°C, which takes into account both the growth of lactic acid bacteria and the decomposition efficiency of xylanase, and the crude protein content generated within this temperature range is the highest.

[0068] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A production method for increasing the crude protein content of defatted rice bran for feeding, characterized in that: The method firstly uses lactic acid bacteria for pretreatment and then uses yeast for fermentation.

2. The method according to claim 1, characterized in that The lactic acid bacteria include one or more of Lactobacillus plantarum, Lactobacillus acidophilus and Lactobacillus casei.

3. The method according to claim 2, characterized in that The lactic acid bacteria include Lactobacillus casei.

4. The method according to claim 3, characterized in that The yeast includes one or more of Kluyveromyces marxianus, Candida utilis, Candida tropicalis, and Anomalisa wickhamii.

5. The method according to claim 4, characterized in that The yeast includes Kluyveromyces marxianus.

6. The method according to claim 5, characterized in that The following steps are involved: (1) Preparation of Kluyveromyces marxianus liquid seeds; (2) bacterial enzyme combined pretreatment of defatted rice bran; (3) Fermentation treatment of Kluyveromyces marxianus.

7. The method according to claim 6, characterized in that The temperature of the heat preservation fermentation in the bacterial enzyme combined pretreatment in step (2) is 35-37°C.

8. A use of lactic acid bacteria for preparing an agent for reducing the pH value of defatted rice bran, characterized in that: The lactic acid bacteria include one or more of Lactobacillus plantarum, Lactobacillus acidophilus and Lactobacillus casei.

9. A use of yeast for preparing a reagent for increasing the crude protein content of defatted rice bran, characterized in that: The yeast includes one or more of Kluyveromyces marxianus, Candida utilis, Candida tropicalis, and Anomalisa wickhamii.

10. The use according to claim 9, characterized in that The yeast includes Kluyveromyces marxianus.

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