Application of fermented sweet potato residues in penaeus vannamei boone feed
The preparation of fermented substances instead of fish meal by using enzymatic lysis and microbial fermentation of sweet potato residues was solved, and the application of sweet potato residues in South American whitening shrimp feed was reduced, and the growth and immune function of South American whitening shrimp was improved, and the intestinal bacterial flora was regulated.
Patent Information
- Application Number
- CN202510640843.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-19
- Publication Date
- 2025-07-08
AI Technical Summary
There is a lack of systematic research and optimization in the existing technology, and the application of sweet potato residue in South American white shrimp feed is not yet perfect, resulting in insufficient research on fish meal replacements, resulting in high breeding costs and great environmental impact.
Sweet potato residues are treated with enzymatic lysis and microbial fermentation, and then fermentation is prepared to replace some fish meal. The specific steps include enzymatic lysis, sterilization, fermentation and high-temperature inactivation, and microorganisms such as Candida prion production, Candida lipolytica, Aspergillus niger and Lactobacillus Bulgaria.
It reduces the cost of breeding, reduces the impact of sweet potato residue waste on the environment, and improves the growth performance, digestive enzyme activity and immune function of South American white shrimps, and regulates the intestinal microbial structure.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of aquaculture feeds, and particularly relates to the application of fermented sweet potato residue in the feed of Litopenaeus vannamei. Background Art
[0002] Litopenaeus vannamei is one of the shrimp species with the highest aquaculture production globally and occupies an important position in aquaculture. In the feed of Litopenaeus vannamei, fish meal usually plays an important role because it provides high-quality protein and other essential nutrients, which helps to promote the growth and development of shrimp. Fish meal is a high-protein feed raw material made from one or more kinds of fish through processes such as defatting, dehydrating, and pulverizing. However, with the decline of global fishery resources, the supply of fish meal has decreased and its price fluctuates greatly, which makes finding suitable fish meal substitutes become a research hotspot in the field of aquaculture. As a by-product of sweet potato processing, sweet potato residue has a large output and contains certain nutrients. If it can be developed as a fish meal substitute and applied in the feed of Litopenaeus vannamei, it can not only reduce the breeding cost but also realize the high-value utilization of resources. However, the current research on the application of sweet potato residue in the feed of Litopenaeus vannamei is not perfect, lacking systematic evaluation and optimization. Summary of the Invention
[0003] Aiming at the above deficiencies, the present invention discloses the application of fermented sweet potato residue in the feed of Litopenaeus vannamei. Using sweet potato residue to replace part of the fish meal to prepare the feed of Litopenaeus vannamei can not only reduce the feed cost and alleviate the environmental impact of sweet potato residue waste, but also the obtained feed can improve the growth performance, digestive enzyme activity, and immune function of Litopenaeus vannamei.
[0004] The present invention is realized by the following technical solutions: The application of a fermented sweet potato residue in the feed of Litopenaeus vannamei is to enzymatically hydrolyze the sweet potato residue and then inoculate microorganisms for fermentation to obtain a fermented product, and then use the fermented product to replace part of the fish meal to produce the feed of Litopenaeus vannamei; the microorganisms include Candida utilis, Candida lipolytica, Aspergillus niger, and Lactobacillus bulgaricus.
[0005] Furthermore, the proportion of using the fermented product to replace fish meal is 28% - 57%.
[0006] Furthermore, the preparation method of the fermented product includes the following steps: (1) Take the pulverized sweet potato residue and mix it evenly with water to obtain a mixture, then add amylase to the mixture and enzymatically hydrolyze it at 90 - 100 °C for 20 - 45 min, and then cool and adjust the pH value to 7.5 - 8.0 to obtain a primary enzymatically hydrolyzed product; (2) Add alkaline protease to the primary enzymatic hydrolysis product obtained in step (1) and carry out enzymatic hydrolysis at 55-65 °C for 20-45 min. Then, after cooling, perform high-temperature sterilization at 121 °C for 15 min, and then cool to obtain the secondary enzymatic hydrolysis product; (3) Add urea and ammonium sulfate to the secondary enzymatic hydrolysis product obtained in step (2) and mix evenly. Then add a compound microbial agent for fermentation. The fermentation temperature is 25-30 °C, and the fermentation time is 64-84 h. After fermentation, inactivate at high temperature to obtain the fermented product; the compound microbial agent contains Candida utilis, Candida lipolytica, Aspergillus niger, and Lactobacillus bulgaricus.
[0007] Further, in step (1), the mass ratio of sweet potato residue to water is 1:1.
[0008] Further, in step (1), the reagents for adjusting the pH value include a hydrochloric acid solution with a concentration of 0.1 mol / L and a sodium hydroxide solution with a concentration of 0.1 mol / L.
[0009] Further, in step (1), the amylase is a heat-resistant α-amylase, and the addition amount of the amylase is 0.3-0.8% of the weight of the mixture.
[0010] Further, in step (2), the addition amount of the alkaline protease is 0.05-0.2% of the weight of the primary enzymatic hydrolysis product.
[0011] Further, in step (3), the addition amount of urea is 2-5% of the weight of the secondary enzymatic hydrolysis product, the addition amount of ammonium sulfate is 2-5% of the weight of the secondary enzymatic hydrolysis product, the compound microbial agent is obtained by mixing Candida utilis, Candida lipolytica, Aspergillus niger, and Lactobacillus bulgaricus according to a weight ratio of 1:1:1:1, and the addition amount of the compound microbial agent is 2-5% of the weight of the secondary enzymatic hydrolysis product.
[0012] Further, in step (3), the pH of the material at the beginning of fermentation is 5-6.
[0013] The beneficial effects of this technical solution compared with the prior art are as follows: The waste sweet potato residues of the present invention are recycled, enzymatically hydrolyzed, and then fermented by mixing with Candida utilis, Candida lipolytica, Aspergillus niger, Lactobacillus bulgaricus, etc. to obtain a fermented product. Then, the fermented product is used to replace part of the fish meal to prepare the feed for Litopenaeus vannamei. This can not only reduce the feeding cost without affecting the yield of Litopenaeus vannamei and alleviate the environmental impact brought by the waste sweet potato residues, but also improve the growth performance, digestive enzyme activity, and immune function of Litopenaeus vannamei when the fermented sweet potato residues replace part of the fish meal. For example, the fermented sweet potato residues replacing fish meal can regulate the intestinal flora structure, reduce the abundance of harmful bacteria (such as Vibrio), and increase the abundance of beneficial bacteria (such as Agarivorans). Description of the Drawings
[0014] Figure 1 It is a schematic diagram of the composition and relative abundance changes of the intestinal flora at the phylum level.
[0015] Figure 2 It is a schematic diagram of the composition and relative abundance changes of the intestinal flora at the genus level.
[0016] Figure 3 It is a class-level classification diagram of the differential metabolites in the liver of Litopenaeus vannamei.
[0017] Figure 4 It is a subclass-level classification diagram of the differential metabolites in the liver of Litopenaeus vannamei.
[0018] Figure 5 It is a general class-level classification diagram of the differential metabolites in the liver of Litopenaeus vannamei. Detailed Embodiments
[0019] The present invention is further illustrated by the following examples, which shall not be construed as limiting the present invention. For the specific experimental conditions and methods not specified in the following examples, the technical means used are generally the conventional means well known to those skilled in the art.
[0020] Example 1: Fermentation based on sweet potato residues for replacing fish meal, which includes the following steps: (1) According to the mass ratio of sweet potato residues to water of 1:1, take the crushed sweet potato residues and mix them evenly with water to obtain a mixture. Then, add amylase to the mixture and enzymatically hydrolyze it at 95°C for 30 min. Then, cool it and adjust the pH value to 7.8 with a hydrochloric acid solution with a concentration of 0.1 mol / L or a sodium hydroxide solution with a concentration of 0.1 mol / L to obtain a primary enzymatically hydrolyzed product; the amylase is a heat-resistant α-amylase, and the addition amount of the amylase is 0.5% of the weight of the mixture; (2) Add alkaline protease to the primary enzymatic hydrolysate obtained in step (1) and carry out enzymatic hydrolysis at 60 °C for 30 min. Then, after cooling, perform high-temperature sterilization at 121 °C for 15 min, and then cool to obtain the secondary enzymatic hydrolysate; the addition amount of the alkaline protease is 0.1% of the weight of the primary enzymatic hydrolysate. (3) Add urea and ammonium sulfate to the secondary enzymatic hydrolysate obtained in step (2) and mix evenly. Then, add a compound bacterial agent for fermentation. At the beginning of fermentation, the pH of the material is 5.5, the fermentation temperature is 28 °C, and the fermentation time is 72 h. After fermentation, inactivate at high temperature to obtain the fermented product; the addition amount of urea is 3% of the weight of the secondary enzymatic hydrolysate, the addition amount of ammonium sulfate is 3% of the weight of the secondary enzymatic hydrolysate. The compound bacterial agent is obtained by mixing Candida utilis, Candida lipolytica, Aspergillus niger, and Lactobacillus bulgaricus according to a weight ratio of 1:1:1:1, and the addition amount of the compound bacterial agent is 3% of the weight of the secondary enzymatic hydrolysate.
[0021] Example 2: Preparation of fermentation for replacing fish meal based on sweet potato residue, which includes the following steps: (1) According to the mass ratio of sweet potato residue to water of 1:1, take the sweet potato residue, crush it and mix it evenly with water to obtain a mixture. Then, add amylase to the mixture and carry out enzymatic hydrolysis at 90 °C for 45 min. Then, after cooling, adjust the pH value to 7.5 with a hydrochloric acid solution with a concentration of 0.1 mol / L or a sodium hydroxide solution with a concentration of 0.1 mol / L to obtain the primary enzymatic hydrolysate; the amylase is thermotolerant α-amylase, and the addition amount of the amylase is 0.3% of the weight of the mixture. (2) Add alkaline protease to the primary enzymatic hydrolysate obtained in step (1) and carry out enzymatic hydrolysis at 55 °C for 45 min. Then, after cooling, perform high-temperature sterilization at 121 °C for 15 min, and then cool to obtain the secondary enzymatic hydrolysate; the addition amount of the alkaline protease is 0.05% of the weight of the primary enzymatic hydrolysate. (3) Add urea and ammonium sulfate to the secondary enzymatic hydrolysate obtained in step (2) and mix evenly. Then, add a compound bacterial agent for fermentation. At the beginning of fermentation, the pH of the material is 5, the fermentation temperature is 25 °C, and the fermentation time is 84 h. After fermentation, inactivate at high temperature to obtain the fermented product; the addition amount of urea is 2% of the weight of the secondary enzymatic hydrolysate, the addition amount of ammonium sulfate is 2% of the weight of the secondary enzymatic hydrolysate. The compound bacterial agent is obtained by mixing Candida utilis, Candida lipolytica, Aspergillus niger, and Lactobacillus bulgaricus according to a weight ratio of 1:1:1:1, and the addition amount of the compound bacterial agent is 2% of the weight of the secondary enzymatic hydrolysate.
[0022] Example 3: Preparation of fermentation for replacing fish meal based on sweet potato residue, which includes the following steps: (1) According to the mass ratio of sweet potato residue to water being 1:1, take the pulverized sweet potato residue and mix it evenly with water to obtain a mixture. Then, add amylase to the mixture and enzymatically hydrolyze it at 98°C for 30 minutes. After that, cool it and adjust the pH value to 7.6 with a hydrochloric acid solution with a concentration of 0.1 mol / L or a sodium hydroxide solution with a concentration of 0.1 mol / L to obtain a primary enzymatically hydrolyzed product; the amylase is a heat-resistant α-amylase, and the addition amount of the amylase is 0.6% of the weight of the mixture. (2) Add alkaline protease to the primary enzymatically hydrolyzed product obtained in step (1) and enzymatically hydrolyze it at 62°C for 30 minutes. Then, cool it and sterilize it at a high temperature of 121°C for 15 minutes, and then cool it to obtain a secondary enzymatically hydrolyzed product; the addition amount of the alkaline protease is 0.1% of the weight of the primary enzymatically hydrolyzed product. (3) Add urea and ammonium sulfate to the secondary enzymatically hydrolyzed product obtained in step (2) and mix them evenly. Then, add a compound microbial agent for fermentation. At the beginning of fermentation, the pH of the material is 5.5, the fermentation temperature is 26°C, and the fermentation time is 80 hours. After fermentation, inactivate it at a high temperature to obtain a fermented product; the addition amount of urea is 4% of the weight of the secondary enzymatically hydrolyzed product, the addition amount of ammonium sulfate is 3% of the weight of the secondary enzymatically hydrolyzed product, the compound microbial agent is obtained by mixing Candida utilis, Candida lipolytica, Aspergillus niger, and Lactobacillus bulgaricus according to a weight ratio of 1:1:1:1, and the addition amount of the compound microbial agent is 4% of the weight of the secondary enzymatically hydrolyzed product.
[0023] Example 4: Fermentation based on sweet potato residue for replacing fish meal, which includes the following steps: (1) According to the mass ratio of sweet potato residue to water being 1:1, take the pulverized sweet potato residue and mix it evenly with water to obtain a mixture. Then, add amylase to the mixture and enzymatically hydrolyze it at 100°C for 20 minutes. After that, cool it and adjust the pH value to 8.0 with a hydrochloric acid solution with a concentration of 0.1 mol / L or a sodium hydroxide solution with a concentration of 0.1 mol / L to obtain a primary enzymatically hydrolyzed product; the amylase is a heat-resistant α-amylase, and the addition amount of the amylase is 0.8% of the weight of the mixture. (2) Add alkaline protease to the primary enzymatically hydrolyzed product obtained in step (1) and enzymatically hydrolyze it at 65°C for 20 minutes. Then, cool it and sterilize it at a high temperature of 121°C for 15 minutes, and then cool it to obtain a secondary enzymatically hydrolyzed product; the addition amount of the alkaline protease is 0.2% of the weight of the primary enzymatically hydrolyzed product. (3) Urea and ammonium sulfate were added to the secondary enzymatic hydrolysate obtained in step (2) and mixed evenly, and then a compound microbial agent was added for fermentation. The initial pH of the material during fermentation was 6, the fermentation temperature was 30 °C, and the fermentation time was 64 h. After fermentation, it was inactivated at high temperature to obtain a fermented product. The addition amount of urea was 5% of the weight of the secondary enzymatic hydrolysate, the addition amount of ammonium sulfate was 5% of the weight of the secondary enzymatic hydrolysate. The compound microbial agent was obtained by mixing Candida utilis, Candida lipolytica, Aspergillus niger, and Lactobacillus bulgaricus according to a weight ratio of 1:1:1:1, and the addition amount of the compound microbial agent was 5% of the weight of the secondary enzymatic hydrolysate.
[0024] Experimental example: Preparation of experimental feed: Taking fish meal as the main raw material and mixing it with auxiliary materials (such as soybean meal, wheat bran, flour, fish oil, minerals, vitamins, calcium dihydrogen phosphate, squid paste, betaine, lysine, and methionine, etc.) to prepare a Pacific white shrimp feed to obtain a control group (FM). Then, sweet potato residue was taken and a fermented product was prepared according to the method described in Example 1. Then, the fermented product was used to replace 28%, 57%, and 86% of the fish meal respectively and mixed with the auxiliary materials to prepare Pacific white shrimp feeds to obtain Application Group 1 (FSP28), Application Group 2 (FSP57), and Application Group 3 (FSP86). The feeds of each group were isocaloric and isonitrogenous.
[0025] Experimental shrimp management: 30-day-old Pacific white shrimp were collected from a Pacific white shrimp breeding base in Fangchenggang, Guangxi for the experiment. The collected Pacific white shrimp were randomly assigned to plastic barrels (400 L) for feeding, with 50 shrimps in each barrel. Every 3 barrels were taken as a group, and there were four groups in total, which were fed the feeds of the control group (FM), Application Group 1 (FSP28), Application Group 2 (FSP57), and Application Group 3 (FSP86) respectively. During the breeding period, they were fed 3 times a day at regular intervals, and the daily feeding amount was 3-8% of the shrimp body weight, and it was dynamically adjusted according to the weather, water temperature, and shrimp body mass. Every day, the feces and residual baits at the bottom of the barrel were removed by siphon method, and 3 / 4 of the seawater in the barrel was replaced every 5-7 days according to the water quality change.
[0026] Experimental detection: Regularly detect the cultured Pacific white shrimp. For example, after 8 weeks of breeding, calculate the growth performance indexes of the Pacific white shrimp, determine the enzyme activities of the liver tissue, determine the body composition of the muscle, detect the metabolites of the liver, and detect the intestinal flora of the intestine.
[0027] Analysis of experimental results: Analyze according to the data obtained from the detection. The feed produced by replacing part of the fish meal with fermented sweet potato residue according to the method of the present invention has significant effects on the growth performance, digestive enzyme activities, immune function, intestinal flora structure, and liver metabolism of Pacific white shrimp.
[0028] For growth performance, see Table 1. The changes in indicators such as the weight gain rate, survival rate, feed conversion ratio, and body composition of Litopenaeus vannamei under different substitution levels intuitively reflect the positive effects of fermented sweet potato residue replacing fish meal on the growth performance of Litopenaeus vannamei within a certain range, as well as the negative effects of excessive substitution amounts. Specifically, there were no significant differences in the weight gain rate and survival rate between the FSP28 group and the FSP57 group compared with the FM group, and the survival rate of the FSP86 group showed a significant decrease; the crude fat content decreased in the FSP57 and FSP86 groups.
[0029] Table 1 Effects of fermented sweet potato residue replacing fish meal on the growth performance of Litopenaeus vannamei Parameters FM FSP28 FSP57 FSP86 WGR% <![CDATA[328.5±19.45 b > <![CDATA[332.33±13.12 b > <![CDATA[316.87±14.04 b > <![CDATA[303.80±22.89 b > FCR% <![CDATA[2.01±0.04 a > <![CDATA[2.11±0.03 a > <![CDATA[2.13±0.06 a > <![CDATA[3.91±0.08 b > SGR(% / d) <![CDATA[2.39±0.05 b > <![CDATA[2.46±0.02 b > <![CDATA[2.42±0.13 b > <![CDATA[2.32±0.85 b > LGR% <![CDATA[48.83±9.14 b > <![CDATA[62.47±2.26 b > <![CDATA[53.63±9.19 b > <![CDATA[49.41±6.19 b > survival% <![CDATA[72.00±2.00 b > <![CDATA[72.00±7.21 b > <![CDATA[68.00±8.72 b > <![CDATA[58.00±2.00 a > Crude protein(mg / g) <![CDATA[517.94±12.92 b > <![CDATA[505.15±11.99 ab > <![CDATA[503.30±1.95 ab > <![CDATA[494.40±12.14 a > Crude lipid(mg / g) <![CDATA[48.6±3.52 b > <![CDATA[49.2±0.30 b > <![CDATA[44.9±1.60 a > <![CDATA[42.3±1.05 a > Ash(%) <![CDATA[15.29±0.92 a > <![CDATA[17.86±0.98 b > <![CDATA[16.55±0.35 ab > <![CDATA[17.32±0.12 b > Moisture content(%) 80.12±1.88 81.72±2.05 81.21±0.93 81.26±0.52 Values with superscript letters a, b in Table 1 were significantly different among columns (P < 0.05).
[0030] For enzyme activities, see Table 2. The effects of fermented sweet potato residue replacing fish meal on the enzyme activities of Litopenaeus vannamei showed the changes in the activities of digestive enzymes and immune enzymes in the liver of Litopenaeus vannamei in each experimental group, which helped to understand the mechanism of action of fermented sweet potato residue replacing fish meal on its digestive and immune functions. Specifically, the activities of protease, POD, and SOD in the FSP86 group were significantly down-regulated.
[0031] Table 2 Effects of fermented sweet potato residue replacing fish meal on the enzyme activities of Litopenaeus vannamei Parameters FM FSP28 FSP57 FSP86 AMS(U / dl) 54.83±1.92 56.04±2.61 55.57±0.60 60.45±4.54 Pepsin(U / mgprot) <![CDATA[4.31±0.01 b > <![CDATA[4.21±0.02 b > <![CDATA[4.17±0.16 b > <![CDATA[3.72±0.16 a > LPS(U / prot) <![CDATA[0.31±0.02 ab > <![CDATA[0.36±0.05 b > <![CDATA[0.33±0.04 ab > <![CDATA[0.29±0.02 a > LZM(U / ml) <![CDATA[78.22±5.45 b > <![CDATA[62.30±1.01 ab > <![CDATA[58.71±4.54 a > <![CDATA[57.62±2.80 a > POD(U / ml) <![CDATA[241.39±7.67 c > <![CDATA[232.89±5.66 c > <![CDATA[213.35±13.01 b > <![CDATA[176.18±14.07 a > SOD(U / ml) <![CDATA[212.14±10.03 b > <![CDATA[203.27±8.29 b > <![CDATA[199.82±8.39 b > <![CDATA[17619±12.98 a > ACP(U / mprot) 117.28±15.49 89.68±25.45 99.79±3.26 109.83±5.81 ALP(U / mprot) 100.75±6.77 96.86±4.98 99.09±4.41 105.98±6.50 Values with superscript letters a, b, c in Table 2 were significantly different among columns (P < 0.05).
[0032] For intestinal flora, see Figure 1 and 2 , Figure 1 and Figure 2 showed the composition and relative abundance changes of intestinal flora at the phylum level and genus level. Replacing fish meal with fermented sweet potato residue could reduce the abundance of harmful bacteria (such as Vibrio) and increase the abundance of beneficial bacteria (such as Agarivorans), indicating that replacing fish meal with fermented sweet potato residue could regulate the intestinal flora structure and affect the abundance of beneficial and harmful bacteria.
[0033] For liver metabolism, see Figures 3 - 5 , Figures 3 - 5 classified and presented the differential metabolites in the liver, providing an intuitive basis for exploring the effects of fermented sweet potato residue replacing fish meal on the liver metabolism of Litopenaeus vannamei. It can be seen that replacing fish meal with a high level of fermented sweet potato residue significantly affected metabolic pathways such as arginine biosynthesis and glycine - serine - threonine metabolism.
[0034] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only an independent technical solution. This narrative style of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. Application of fermented sweet potato residue in feed for whiteleg shrimp, characterized in that: The application is to ferment sweet potato residue after enzymatic hydrolysis by inoculating microorganisms to obtain a fermented product, and then use the fermented product to replace part of the fish meal to produce Litopenaeus vannamei feed; the microorganisms include Candida utilis, Candida lipolytica, Aspergillus niger, and Lactobacillus bulgaricus.
2. The application of fermented sweet potato residue in the feed of Litopenaeus vannamei according to claim 1, wherein: The proportion of replacing fish meal with the fermented product is 28% - 57%.
3. The application of the fermented sweet potato residue according to claim 1 in the feed for whiteleg shrimp, characterized in that: The preparation method of the fermented product includes the following steps: (1) Take the crushed sweet potato residue and mix it evenly with water to obtain a mixture, then add amylase to the mixture and carry out enzymatic hydrolysis at 90 - 100 °C for 20 - 45 min, and then cool and adjust the pH value to 7.5 - 8.0 to obtain a primary enzymatic hydrolysis product; (2) Add alkaline protease to the primary enzymatic hydrolysis product obtained in step (1) and carry out enzymatic hydrolysis at 55 - 65 °C for 20 - 45 min, then cool and sterilize at 121 °C for 15 min, and then cool to obtain a secondary enzymatic hydrolysis product; (3) Add urea and ammonium sulfate to the secondary enzymatic hydrolysis product obtained in step (2) and mix evenly, then add a compound microbial agent for fermentation, the fermentation temperature is 25 - 30 °C, the fermentation time is 64 - 84 h, and after fermentation, inactivate at high temperature to obtain a fermented product; the compound microbial agent contains Candida utilis, Candida lipolytica, Aspergillus niger, and Lactobacillus bulgaricus.
4. The application of the fermented sweet potato residue according to claim 3 in the feed for whiteleg shrimp, characterized in that: In step (1), the mass ratio of sweet potato residue to water is 1:
1.
5. The application of the fermented sweet potato residue according to claim 3 in the feed for Litopenaeus vannamei, characterized in that: In step (1), the reagents for adjusting the pH value include a hydrochloric acid solution with a concentration of 0.1 mol / L and a sodium hydroxide solution with a concentration of 0.1 mol / L.
6. The application of the fermented sweet potato residue according to claim 3 in the feed for whiteleg shrimp, characterized in that: In step (1), the amylase is a thermotolerant α - amylase, and the addition amount of the amylase is 0.3 - 0.8% of the weight of the mixture.
7. The application of the fermented sweet potato residue according to claim 3 in the feed for Litopenaeus vannamei, characterized in that: In step (2), the addition amount of the alkaline protease is 0.05 - 0.2% of the weight of the primary enzymatic hydrolysis product.
8. The application of the fermented sweet potato residue according to claim 3 in the feed for Litopenaeus vannamei, characterized in that: In step (3), the addition amount of urea is 2 - 5% of the weight of the secondary enzymatic hydrolysis product, the addition amount of ammonium sulfate is 2 - 5% of the weight of the secondary enzymatic hydrolysis product, the compound microbial agent is obtained by mixing Candida utilis, Candida lipolytica, Aspergillus niger, and Lactobacillus bulgaricus according to a weight ratio of 1:1:1:1, and the addition amount of the compound microbial agent is 2 - 5% of the weight of the secondary enzymatic hydrolysis product.
9. The application of the fermented sweet potato residue according to claim 3 in the feed for Litopenaeus vannamei, characterized in that: In step (3), the pH of the material at the beginning of fermentation is 5 - 6.