Method for removing zearalenone in guniting corn bran and improving and optimizing nutritional value of guniting corn bran by using Aspergillus niger strain FS10

Abstract

The invention discloses an aspergillus niger strain FS10 for removing zearalenone in guniting corn bran and improving and optimizing the nutritional value of the guniting corn bran, and belongs to the technical field of microbiology and biodegradation. According to the method disclosed by the invention, the guniting corn bran is fermented by utilizing the aspergillus niger strain FS10, and the removal rate of ZEN in the guniting corn bran after fermentation reaches 70.04%; meanwhile, the content of crude protein is increased by 2.02%, the content of total amino acid is increased by 2.27%, the content of proline and glutamic acid is in the front, and the content of essential amino acid is increased by 0.75% compared with that before fermentation, so that resource utilization of the guniting corn bran subjected to fermentation detoxification as animal feed is further promoted.

Description

Technical Field

[0001] The invention relates to the field of microbiology and biodegradation technology, and in particular to the removal of zearalenone in sprayed corn husks by Aspergillus niger strain FS10 and the optimization of nutritional value improvement. Background Art

[0002] Corn is the largest food crop in my country and one of the most consumed crops in my country. Sprayed corn husk is one of the main by-products in the production of corn starch. It has high nutritional value because it is sprayed with high-protein and high-energy corn slurry and is mainly used as animal feed. Sprayed corn husk is obtained by spraying and fermenting concentrated corn slurry. The fungal toxins in the corn raw material will be concentrated and enriched in the by-product sprayed corn husk during the processing process, resulting in its safe application in the feed industry being limited.

[0003] According to data, zearalenone (ZEN) is the most seriously contaminated among corn and corn by-products nationwide. GB 2761-2017 "National Food Safety Standard Limits of Fungal Toxins in Food" stipulates that the ZEN content in corn shall not exceed 60μg / kg; GB 13078-2017 "Feed Hygiene Standard" stipulates that the maximum allowable content of ZEN in corn feed raw materials is 500μg / kg, and the maximum allowable content of ZEN in sprayed corn husks is 1500μg / kg. However, in the 2019-2020 survey, it was found that the detection rate of ZEN in corn by-products reached 100%, the excess rate reached 9.63%, and the average detection content reached 233.70 and 739.51μg / kg in two years respectively. This shows that the degree of ZEN contamination of corn by-products, including sprayed corn husks, has an upward trend. Therefore, the pollution problem of ZEN in sprayed corn husks should be given important attention.

[0004] ZEN pollution not only harms humans and animals, but also causes direct economic losses in food. Currently, the methods for removing ZEN are mainly divided into physical, chemical and biological methods. However, physical and chemical methods are non-targeted removal of ZEN, and to a certain extent, they will destroy the nutritional components of food raw materials and feed. In addition, the addition of chemical substances may also produce toxic substances and cause safety hazards, which further limits the development of physical and chemical methods. Unlike physical and chemical methods, biological methods have the characteristics of mild action conditions, high specificity and economy, showing great application prospects, and have begun to enter the public eye and receive widespread attention from the research community.

[0005] Some studies have reported on the use of biological strains to remove ZEN from feed. Xu et al. screened a starch liquefaction Bacillus strain that can efficiently degrade ZEN, and the degradation rate of ZEN in actual contaminated wheat samples by this strain reached 62.1%. Guo Rui et al. mixed Bacillus cereus with two lactic acid bacteria for solid-state aerobic fermentation of feed raw materials and found that it can completely degrade ZEN in feed, and the fermented feed is safe and feedable. However, the fiber content in corn husk is high, and ZEN can easily form stable compounds with cellulose in corn husk, which increases the difficulty of biodegradation. In addition, since microorganisms consume nutrients while degrading ZEN, it is difficult to ensure that the nutrients in corn husk are not lost. Therefore, it is of great significance to find a biodegradation method that can effectively degrade ZEN in corn husk and maintain the nutrients in corn husk. Summary of the invention

[0006] In order to overcome the shortcomings and deficiencies of the prior art, the purpose of the present invention is to use a food-grade non-toxigenic Aspergillus niger strain FS10 as a fermentation strain to degrade zearalenone toxin during the fermentation process.

[0007] One object of the present invention is to improve the quality of corn bran through fermentation of the Aspergillus niger FS10 strain.

[0008] In one embodiment, the improvement of corn husk quality is to reduce the content of zearalenone in corn germ meal and improve the nutritional content of corn husk.

[0009] In one embodiment, the improvement of the nutritional components of corn husk is to increase the amino acid content in the corn husk; the amino acid includes at least one of alanine, leucine, phenylalanine, and histidine.

[0010] In one embodiment, corn husks are inoculated with a final concentration of (1×10 4 )~(2x10 5 ) CFU / mL of Aspergillus niger FS10.

[0011] In one embodiment, the fermentation is carried out at 20-40°C for at least 2 days.

[0012] In one embodiment, water is added to corn husks for fermentation, and the mass volume ratio of corn husks to water is (1:0.8) to (1:1.6) g / mL.

[0013] In one embodiment, the concentration of FS10 spore suspension was fixed at 10 6CFU / mL, selected four influencing factors, namely, feed-water ratio, inoculation amount, fermentation temperature and fermentation time, and carried out single factor experiment with ZEN removal rate as an indicator to explore the influence of each factor on ZEN removal rate in sprayed corn husk. ZEN removal rate calculation method is: ZEN removal rate (%) = (ZEN content in unfermented sample - ZEN content in fermented sample) / ZEN content in unfermented sample × 100

[0014] In one embodiment, the response surface method factor level experimental design, according to the above single factor results, uses the Design expert11 software to apply the Box-Behnken design method, takes the inoculation amount (A), fermentation temperature (B), fermentation time (C), and material-water ratio (D) as the response variables, selects the ZEN removal rate as the response value, and performs the response surface optimization design.

[0015] In one embodiment, the optimal parameters for removing ZEN are analyzed by Design Expert 11 software as follows: inoculation amount 11.82%, fermentation temperature 25.50°C, fermentation time 5.48 days, and material-water ratio 1:1.4. The predicted ZEN removal rate under these conditions is 68.33%. Based on the feasibility of actual operation, the inoculation amount 12%, fermentation temperature 26°C, fermentation time 5.5 days, and material-water ratio 1:1.4 were selected for spraying corn husk biofermentation experiments. The actual ZEN removal rate obtained under three parallel experiments was (70.04±1.88)%, and the relative error with the theoretical value was 1.71%.

[0016] The optimization of the removal conditions of zearalenone from sprayed corn husk by Aspergillus niger strain FS-10 includes the following steps:

[0017] (1) 100 μL of Aspergillus niger strain FS-10 was inoculated on PDA medium, evenly spread with a disposable sterile coating rod, and cultured in a 28°C constant temperature incubator for 5 days. Then, Aspergillus niger was scraped with a sterile inoculation loop and inoculated into new PDA medium, and cultured in a 28°C constant temperature incubator for 5 days to obtain a stably cultured Aspergillus niger FS10 strain.

[0018] PDA medium: 5 g potato powder, 20 g glucose, 15 g agar, 0.1 g chloramphenicol, natural pH, distilled water to 1000 mL, sterilize at 121°C for 20 min.

[0019] Sterile physiological saline solution containing 0.05% Tween-80: 9g sodium chloride is dissolved in 1000mL distilled water, after dissolution, 500μL Tween-80 is added and mixed, and sterilized at 121℃ for 20min.

[0020] (2) Preparation of spore suspension: The spores of the strain cultured in step (1) were rinsed with sterilized saline containing 0.05% Tween-80 and the spore concentration was adjusted to 10 6 CFU / mL, for future use.

[0021] (3) Sprayed corn husk biofermentation treatment: The sprayed corn husk was crushed, passed through a 50-mesh sieve, mixed, and collected in a glass container, sterilized, and cooled to room temperature for later use.

[0022] Refer to GB / T 14699-2023 "Feed Sampling" for aseptic sampling of sprayed corn husks, accurately weigh 5 g of sample and place it in a disposable sterile culture dish, add sterile water to adjust the feed-water ratio, add the FS10 spore suspension with the concentration adjusted in step (2) to adjust the inoculation amount. After stirring evenly, place it in a constant temperature incubator for constant temperature aerobic fermentation for a certain period of time under certain temperature conditions.

[0023] Determination of ZEN in sprayed corn husk: Weigh 1g sample, add ultrapure water and chloroform in turn according to the solid-liquid ratio of 1:3 (g:mL), fully vortex, ultrasonicate, centrifuge, collect the lower chloroform layer, and repeat the extraction 3 times. Dry in a vacuum freeze dryer, re-dissolve in methanol, pass through a 0.22μm ultrafiltration membrane, and transfer to a chromatographic vial for testing.

[0024] Prepare a ZEN standard solution with a mass concentration gradient of 10, 20, 50, 100, 200, 500, 1000, 2000, 5000 mg / L. The liquid chromatography conditions are as follows: a C18 reverse phase column (Thermo Hypersil Gold C18, 150 mm × 4.6 mm, 3.5 μm) and a UV detector (VWD, 254 nm) are used. The injection volume is 20 μL, the sample is isocratically eluted at a flow rate of 0.6 mL / min, the mobile phase is a mixture of acetonitrile / water (60:40, V / V), the column temperature is 30 ° C, and the elution time is 15 min.

[0025] Another object of the present invention is to provide the use of Aspergillus niger FS10 in improving the amino acid content of corn husk.

[0026] In one embodiment, the amino acids include alanine, leucine, phenylalanine and / or histidine.

[0027] Another object of the present invention is to increase the protein content in the sprayed corn husk by fermentation, and also to improve its nutritional value as animal feed.

[0028] The crude protein and amino acid contents of sprayed corn husks before and after fermentation were determined. The crude protein in sprayed corn husks was detected with reference to GB / T 6432-2018 “Determination of crude protein in feeds - Kjeldahl method”; the amino acids in sprayed corn husks were detected with reference to GB / T 18246-2019 “Determination of amino acids in feeds”.

[0029] The results showed that the crude protein content in the sprayed corn husk before and after fermentation was (19.92±0.20)% and (21.94±0.42)%, respectively. Compared with before fermentation, the crude protein content in the sprayed corn husk after fermentation increased by 2.02%. The sprayed corn husk contained a rich variety of amino acids, and the total amino acid content after fermentation increased by 2.27g / 100g compared with before fermentation. Among them, the proline content was the highest at 3.58g / 100g, followed by glutamic acid at 3.33g / 100g. In addition, the essential amino acid content in the sprayed corn husk after fermentation increased by 0.75g / 100g compared with that before fermentation. Therefore, the sprayed corn husk after fermentation and detoxification still has a high feeding value. Aspergillus niger FS10 can not only detoxify the sprayed corn husk, but also improve its nutritional value as animal feed, which provides a good idea and experimental guidance for the rational utilization and full development of the sprayed corn husk.

[0030] Another object of the present invention is to provide the use of Aspergillus niger FS10 in preparing feed with corn husk as the main raw material.

[0031] Beneficial effects:

[0032] (1) The optimal fermentation conditions for Aspergillus niger FS10 to remove ZEN from sprayed corn husks were as follows: inoculation amount 12%, fermentation temperature 26°C, fermentation time 5.5 days, and feed-water ratio 1:1.4. Under these conditions, the removal rate of ZEN from sprayed corn husks by Aspergillus niger strain reached 70.04%.

[0033] (2) After fermentation with Aspergillus niger, the crude protein content in the sprayed corn husk increased by 2.02%, and the total amino acid content increased by 2.27%, among which alanine, leucine, phenylalanine, histidine and arginine increased by 0.35%, 0.33%, 0.09%, 0.11% and 0.22% respectively. These amino acids are important flavor precursors. They can undergo Maillard reaction with reducing sugars or other carbonyl compounds to generate a variety of flavor substances, significantly improving the flavor of the sprayed corn husk. This further facilitates the resource utilization of the fermented and detoxified sprayed corn husk as animal feed. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Effect of inoculum size on ZEN removal by Aspergillus niger;

[0035] Figure 2Effect of fermentation temperature on ZEN removal by Aspergillus niger;

[0036] Figure 3 Effect of fermentation time on ZEN removal by Aspergillus niger;

[0037] Figure 4 Effect of feed-water ratio on ZEN removal by Aspergillus niger;

[0038] Figure 5 Response surface diagram of the effects of pairwise interactions of factors on ZEN removal rate. DETAILED DESCRIPTION

[0039] The present invention is described below by specific embodiments. Unless otherwise specified, the technical means used in the present invention are methods known to those skilled in the art. In addition, the embodiments should be understood as illustrative rather than limiting the scope of the present invention, and the essence and scope of the present invention are limited only by the claims. For those skilled in the art, various changes or modifications to the material composition and dosage in these embodiments, without departing from the essence and scope of the present invention, also belong to the protection scope of the present invention. The raw materials and reagents used in the present invention are all commercially available.

[0040] The Aspergillus niger FS10 strain used in the following examples has been disclosed in the document "Optimization of the degradation ability of Aspergillus niger FS10 on zearalenone and study of its mechanism".

[0041] The ZEN standard products involved in the following examples were purchased from Qingdao Puruibang with the product number of STD#3202; the sprayed corn husks were purchased from Shandong Xiwang Group.

[0042] The "inoculum amount" involved in the following examples refers to the percentage of the volume of bacterial liquid to the mass of sprayed corn husks (mL:g); the "material-water ratio" refers to the ratio of the mass of sprayed corn husks to the volume of sterile water, g:mL.

[0043] The detection methods involved in the following embodiments are as follows:

[0044] Determination of ZEN in sprayed corn husk:

[0045] Weigh 1g of sample, add ultrapure water and chloroform in turn according to the solid-liquid ratio of 1:3 (g:mL), vortex thoroughly and mix well, then sonicate for 10min, then centrifuge at 25℃ and 8000r / min for 10min, collect the lower chloroform layer, and repeat the extraction 3 times. Dry in a vacuum freeze dryer for 3 hours, then add 1mL of 50% methanol for redissolution, pass through a 0.22μm ultrafiltration membrane and transfer to a chromatographic vial for testing.

[0046] Prepare a ZEN standard solution with a mass concentration gradient of 10, 20, 50, 100, 200, 500, 1000, 2000, 5000 mg / L. The liquid chromatography conditions are as follows: a C18 reverse phase column (Thermo Hypersil Gold C18, 150 mm × 4.6 mm, 3.5 μm) and a UV detector (VWD, 254 nm) are used. The injection volume is 20 μL, the sample is isocratically eluted at a flow rate of 0.6 mL / min, the mobile phase is a mixture of acetonitrile / water (60:40, V / V), the column temperature is 30 ° C, and the elution time is 15 min.

[0047] The calculation method of ZEN removal rate is: ZEN removal rate (%) = (ZEN content in unfermented sample - ZEN content in fermented sample) / ZEN content in unfermented sample × 100. The ZEN content in the unfermented sample was detected to be 67.28 ng / g.

[0048] Example 1: Effect of the inoculum size of Aspergillus niger FS10 on the removal of zearalenone

[0049] 1. Activation of Aspergillus niger FS10 strain and preparation of spore suspension:

[0050] First, take out the frozen Aspergillus niger FS10 bacterial liquid from -80℃ and thaw it at room temperature, then take 100μL and inoculate it on the PDA medium, spread it evenly with a disposable sterile coating rod, and place it in a 28℃ constant temperature incubator for 5 days. Then, use a sterile inoculation loop to scrape Aspergillus niger and inoculate it into a new PDA medium, and place it in a 28℃ constant temperature incubator for 5 days to obtain a stable passage Aspergillus niger FS10 strain. Then, wash the Aspergillus niger spores with sterile saline containing 0.05% Tween-80 as a spore suspension, and adjust the concentration to 10 6 CFU / mL, for future use.

[0051] 2. Spraying corn husk bio-fermentation treatment:

[0052] The sprayed corn husks were crushed, mixed through a 50-mesh sieve, and collected in a glass container. After sealing with gauze and newspaper, they were sterilized in an autoclave (121°C, 20 min) and cooled to room temperature for later use. The sprayed corn husks were sampled aseptically according to GB / T 14699-2023 "Feed Sampling", and 5 g of the sample was accurately weighed and placed in a disposable sterile culture dish.

[0053] The prepared Aspergillus niger FS10 spore suspension was inoculated at 1%, 5%, 10%, 15%, and 20% (corresponding to the inoculation concentration of 1×10 4 , 5x10 4 , 1x10 5 , 1.5x10 5 , 2x105 CFU / mL) were fully mixed with sterile water (the total volume of spore liquid and sterile water was 5 mL, that is, the material-water ratio was 1:1), poured into the sprayed corn husk and fully stirred, placed in an incubator at 30°C for constant temperature fermentation for 4 days, and then taken out to detect the ZEN content in the corn husk and the fermented corn husk, and the ZEN removal rate was calculated.

[0054] like Figure 1 As shown in the figure, with the increase of the inoculum size of Aspergillus niger, the removal of ZEN in the sprayed corn husk generally showed an increasing trend and then tended to be stable. When the inoculum size was 1% to 10%, the ZEN removal rate increased with the increase of the inoculum size. When the inoculum size was 10%, the removal rate reached a maximum value of 66.79%. When the inoculum size was 15% to 20%, the ZEN removal rate decreased slightly and then tended to be stable. It shows that too much or too little inoculum will affect its growth in the sprayed corn husk, and then produce different ZEN removal effects. Too little inoculum will cause the growth delay period of the bacteria to be too long, thereby extending its fermentation cycle; too much inoculum will cause the mycelium to grow too fast, so that the microorganisms form a strong competitive relationship in the fermentation system, which may inhibit its growth in the fermentation system. Therefore, 10% is selected as the more suitable inoculum size. When the inoculum size is 10%, the ZEN content in the fermented corn husk is 22.34ng / g.

[0055] Example 2: Effect of fermentation temperature on ZEN removal rate in sprayed corn husk

[0056] The biofermentation of sprayed corn husk was carried out according to the method in Example 1, except that the inoculation amount of the fixed Aspergillus niger FS10 spore suspension was 10%. After inoculation, the fermented products were placed in incubators at 20°C, 25°C, 30°C, 35°C, and 40°C for constant temperature fermentation for 4 days, and then taken out. The ZEN content in the fermentation products was detected, and the ZEN removal rate was calculated.

[0057] like Figure 2 As shown in the results, when the fermentation temperature was 20℃~25℃, the ZEN removal rate continued to rise with the increase of temperature, and reached a maximum of 61.42% at 25℃; thereafter, as the temperature continued to rise, the ZEN removal rate showed a cliff-like decline. This may be due to the fact that the temperature of the fermentation system deviated from the optimal growth temperature of Aspergillus niger. As the temperature increased, the enzymatic reaction rate accelerated, and the bacteria grew and multiplied quickly, but the higher the temperature, the faster the enzyme inactivation would be, thus affecting the normal growth of the bacteria. Therefore, 25℃ was selected as the most suitable fermentation temperature. When the fermentation temperature was 25℃, the ZEN content in the corn husk after fermentation was 25.96ng / g.

[0058] Example 3: Effect of fermentation time on ZEN removal rate in sprayed corn husk

[0059] The biofermentation of sprayed corn husk was carried out according to the method in Example 1, except that the inoculation amount of the fixed Aspergillus niger FS10 spore suspension was 10%. After inoculation, the fermented products were placed in an incubator at 30° C. and fermented at constant temperature for 2 days, 3 days, 4 days, 5 days, and 6 days, and then taken out. The ZEN content in the fermentation products was detected, and the ZEN removal rate was calculated.

[0060] like Figure 3 As shown in the figure, within 2 to 5 days of fermentation, the ZEN removal rate gradually increased, and reached a maximum of 65.74% after 5 days of fermentation; on the 6th day of fermentation, the ZEN removal rate decreased slightly, which may be due to the slightly long fermentation time, and the necessary substances for the growth of Aspergillus niger were limited, resulting in a decrease in the fermentation activity of Aspergillus niger, thus affecting the process of solid-state fermentation of sprayed corn husk. Therefore, 5 days was selected as the optimal fermentation time. After 5 days of fermentation, the ZEN content in the fermented corn husk was 23.05ng / g.

[0061] Example 4: Effect of material-water ratio on ZEN removal rate in sprayed corn husk

[0062] The biological fermentation of sprayed corn husk was carried out according to the method in Example 1, except that the inoculation amount of the fixed Aspergillus niger FS10 spore suspension was 10%, the material-water ratio was adjusted to 1:0.8, 1:1, 1:1.2, 1:1.4, and 1:1.6, and after inoculation, the products were placed in an incubator at 30° C. for constant temperature fermentation for 4 days and then taken out, the ZEN content in the fermentation products was detected, and the ZEN removal rate was calculated.

[0063] like Figure 4 As shown in the figure, when the feed-water ratio is 1:0.8-1:1.2, the ZEN removal rate gradually increases, and when the feed-water ratio is 1:1.2, the removal rate reaches a maximum of 64.44%, and when the feed-water ratio is 1:1.4-1:1.6, the ZEN removal rate begins to show a downward trend. This shows that too much or too little water in the system is not conducive to the removal of ZEN in the sprayed corn husk by Aspergillus niger. When the water content in the system is too low, the fermentation environment is too dry, which may cause the microorganisms to grow very slowly or not grow, thereby affecting the fermentation process; if the water content in the system is too high, it may cause insufficient oxygen mass transfer, limit the growth of mycelium and reduce the fungal biomass. Therefore, 1:1.2 is selected as the most suitable feed-water ratio. When the feed-water ratio is 1:1.2, the ZEN content in the corn husk after fermentation is 23.92ng / g.

[0064] Example 5: Response surface method optimization of zearalenone removal conditions by Aspergillus niger FS10:

[0065] According to the above single factor results, the Box-Behnken design method was applied using Design expert11 software, with inoculation amount (A), fermentation temperature (B), fermentation time (C), and material-water ratio (D) as response variables, and ZEN removal rate as the response value, to perform response surface optimization design. The experimental factors and level design are detailed in Table 1.

[0066] Table 1 Response surface experimental factors and levels design

[0067]

[0068] The results of the single factor experiment obtained the optimal fermentation parameters of inoculation amount, fermentation temperature, fermentation time and material-water ratio. Then, the ZEN removal rate was selected as the reference index, and the response surface method was used to conduct a response surface optimization experiment on four factors and three levels. The optimal parameters for removing ZEN from sprayed corn husk by fermentation of Aspergillus niger were obtained through the interaction of each factor. The response surface experiment design and results are shown in Table 2.

[0069] Table 2 Response surface experimental design and results

[0070]

[0071]

[0072] Establishment and analysis of response surface regression model

[0073] The experimental results were regressed and analyzed by variance using Design Expert 11, and a quadratic multinomial regression model was obtained with ZEN removal rate (Y) as the response value and inoculation size (A), fermentation temperature (B), fermentation time (C), and material-water ratio (D) as the response variables: Y = 61.68 + 3.66A + 4.17B + 7.74C + 7.64D + 3.71AB + 3.73AC - 2.96AD - 5.71BC + 1.12BD + 1.59CD - 3.92A2 - 19.72B2 - 10.62C2 - 3.60D2. In order to test the effectiveness of the regression model, variance and significance analysis were performed on the regression model. The results are shown in Table 3.

[0074] Table 3 Analysis of variance of quadratic multinomial regression model for ZEN removal rate

[0075]

[0076] Note: NS has no significant effect; *Significant difference P<0.05; **Highly significant difference P<0.01; ***Extremely significant difference P<0.001

[0077] Establishment and analysis of response surface regression model

[0078] The response surface diagram of the four influencing factors of ZEN removal from sprayed corn husk by Aspergillus niger fermentation: inoculation amount (A), fermentation temperature (B), fermentation time (C), and material-water ratio (D) on the ZEN removal rate in sprayed corn husk is shown in the figure. Figure 5 As shown in Table 3, it can be seen that the interaction term BC, that is, the interaction between fermentation temperature and fermentation time, is significant (P < 0.05), while the significance analysis of the test results of interaction terms AB, AC, AD, BD, and CD is P > 0.05, indicating that the interaction between other interaction terms is not significant. The three-dimensional response surface shows the effect of the interaction between each factor on the ZEN removal rate, and the steepness of its slope can reflect whether the difference between the two factors is obvious. Figure 5 As shown in the figure, each response surface model is a convex surface. As the corresponding factor values ​​increase, each response value first increases to an extreme value and then decreases. The highest point (the center of the plane contour map) is the stable point where the ZEN removal rate reaches the maximum value under this condition.

[0079] Determination of the optimal conditions for response surface analysis

[0080] The optimal parameters for removing ZEN were analyzed by Design Expert 11 software: inoculation amount of 11.82%, fermentation temperature of 25.50℃, fermentation time of 5.48 days, and material-water ratio of 1:1.4. The predicted ZEN removal rate under these conditions was 68.33%. Based on the feasibility of actual operation, the inoculation amount of 12%, fermentation temperature of 26℃, fermentation time of 5.5 days, and material-water ratio of 1:1.4 were selected for the spray corn husk biofermentation experiment. The actual ZEN removal rate obtained under three parallel experiments was (70.04±1.88)%, and the relative error with the theoretical value was 1.71%, indicating that the optimization parameters of the conditions were feasible, and the equation model could be used to optimize the fermentation conditions, and the results obtained were reliable and statistically significant. At this time, the ZEN content in the fermented corn husk was 20.18ng / g.

[0081] Example 6: Evaluation of nutrients in sprayed corn husks under optimal fermentation parameters

[0082] The crude protein in the sprayed corn husk was detected with reference to GB / T 6432-2018 "Determination of crude protein in feed by Kjeldahl method"; the amino acids in the sprayed corn husk were detected with reference to GB / T 18246-2019 "Determination of amino acids in feed". The sprayed corn husk was solid-state fermented under the optimal fermentation conditions, and the crude protein content in the sprayed corn husk before and after fermentation was determined, and the composition and content of amino acids were determined. The results showed that the crude protein content in the sprayed corn husk before and after fermentation was (19.92±0.20)% and (21.94±0.42)%, respectively. Compared with before fermentation, the crude protein content in the sprayed corn husk after fermentation increased by 2.02%. The composition and content of amino acids in the sprayed corn husk before and after fermentation are shown in Table 4. There are rich types of amino acids in the sprayed corn husk, and the total amino acid content after fermentation increased by 2.27g / 100g compared with before fermentation. Among them, the content of proline is the highest at 3.58g / 100g, followed by glutamic acid at 3.33g / 100g. In addition, the content of essential amino acids in the sprayed corn husk after fermentation increased by 0.75g / 100g compared with that before fermentation. Studies have shown that amino acids have an important influence on the flavor and taste of food by affecting the sweetness, bitterness, umami taste of food and acting as flavor precursors. For example, alanine has a sweet taste and can enhance the sweetness perception of food and feed. Leucine has a bitter taste. They play a key role in regulating the flavor of food and feed. For feed raw materials containing higher crude fiber, the addition of amino acids can improve the texture of the feed, make it softer, and increase the feed intake of animals. Therefore, the sprayed corn husk after fermentation and detoxification still has a high feeding value.

[0083] Table 4 Changes in amino acid composition in sprayed corn husk before and after Aspergillus niger solid-state fermentation

[0084]

[0085]

[0086] Note: Different letters indicate significant differences (P<0.05).

[0087] Example 7: Preparation of feed with low ZEN content and high flavor substance content

[0088] Specific implementation method Referring to Example 6, after the corn husk is fermented, it is sterilized in a high-pressure steam autoclave at 121°C and 101kPa for 20 minutes. The sterilized fermented germ meal is dried in a constant temperature hot air drying phase at 80°C for two hours to obtain the fermented corn husk feed with low ZEN content and high flavor substances.

[0089] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for improving corn husk quality, characterized in that: Corn husks were inoculated with Aspergillus niger FS10 for fermentation.

2. The method according to claim 1, characterized in that The method for improving the quality of corn husk is to reduce the content of zearalenone in corn germ meal and improve the nutritional components of corn husk.

3. The method according to claim 2, characterized in that The method for improving the nutritional components of corn husk is to increase the amino acid content in the corn husk; the amino acid includes at least one of alanine, leucine, phenylalanine and histidine.

4. The method according to any one of claims 1 to 3, characterized in that: The corn husk was inoculated with a final concentration of (1x10 4 )~(2x10 5 ) CFU / mL of Aspergillus niger FS10.

5. The method according to claim 4, characterized in that Ferment at 20-40℃ for at least 2 days.

6. The method according to claim 5, characterized in that Water is added to corn husks for fermentation, and the mass volume ratio of corn husks to water is (1:0.8) to (1:1.6) g / mL.

7. Application of Aspergillus niger FS10 in improving the amino acid content of corn husk.

8. The use according to claim 7, characterized in that: The amino acid includes at least one of alanine, leucine, phenylalanine and histidine.

9. Application of Aspergillus niger FS10 in increasing the protein content of corn bran.

10. Application of Aspergillus niger FS10 in the preparation of feed with corn husk as the main raw material.

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