Method for producing selenium-rich protein feed through multi-bacterium synergistic fermentation of Hami melons

Abstract

The invention relates to the technical field of microbial fermentation, and discloses a method for producing selenium-rich protein feed by multi-bacteria synergistic fermentation of Hami melons, which comprises the following steps: crushing Hami melons, mixing with a carbon source and a nitrogen source, inoculating a leavening agent, and fermenting; and drying and crushing the fermented product to obtain the protein feed. The leavening agent comprises candida utilis, aspergillus niger and bacillus licheniformis; the candida utilis culture medium comprises the following components: 9.56 g / L of yeast extract, 19.86 g / L of glucose, 1.45 g / L of dipotassium phosphate, 1.12 g / L of magnesium sulfate, 25 mg / L of sodium selenite, L-lysine and vitamin B1, and the mass concentration ratio of the sodium selenite to the L-lysine to the vitamin B1 is 1: (116-232): (0.06-0.12). According to the invention, the cantaloupe is cooperatively fermented by adopting multiple bacteria, so that the selenium-enriched protein feed is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of microbial fermentation, in particular to a method for producing selenium-enriched protein feed by multi-bacteria cooperative fermentation of Hami melon. Background Art

[0002] Protein feed refers to beans, cakes and dregs, fish meal, etc., with a natural moisture content of less than 45%, crude fiber in dry matter less than 18%, and crude protein content in dry matter reaching or exceeding 20%. There are four major categories of plant-based and animal-based protein feeds. my country is short of protein feed resources and needs to rely on imports, which affects the development of the feed industry and animal husbandry. Unconventional protein feed resources are abundant and have great development potential. As an important trace element, selenium plays a vital role in the immune system, antioxidant capacity, and growth and development of animals. It helps to enhance immune response, reduce the occurrence of diseases, protect cells from oxidative damage, and promote reproduction and improve the quality of animal products such as meat and eggs.

[0003] Hami melons are mainly produced in the Tuha Basin (a general term for the Turpan Basin and the Hami Basin). They have various shapes, unique flavors, thick flesh, crisp and refreshing taste, and rich nutrition, with a sugar content of up to 21%. The production of Hami melons in Xinjiang Uygur Autonomous Region of my country is sufficient, and there is even a phenomenon that they cannot be processed in time and rot in the fields. Therefore, making full use of the excess Hami melons is an urgent problem that Xinjiang Uygur Autonomous Region needs to solve.

[0004] Using Hami melon as a raw material for feed production can not only produce selenium-rich protein feed, but also make full use of excess Hami melon. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for producing selenium-rich protein feed by using multiple bacteria to synergistically ferment Hami melon. In the present invention, multiple bacteria are used to synergistically ferment Hami melon to obtain a selenium-rich protein feed.

[0006] The present invention provides a method for producing selenium-rich protein feed by multi-bacteria cooperative fermentation of Hami melon, comprising the following steps: The cantaloupe is crushed, and then mixed with a carbon source and a nitrogen source, and then a fermentation agent is inoculated to ferment; the fermented product is dried and crushed to obtain a protein feed; The fermentation agent includes Candida utilis, Aspergillus niger, and Bacillus licheniformis; The method for preparing the bacterial liquid of Candida utilis comprises: culturing the Candida utilis in a Candida utilis culture medium, The components of the Candida utilis culture medium include 9.56 g / L yeast extract, 19.86 g / L glucose, 1.45 g / L potassium dihydrogen phosphate, 1.12 g / L magnesium sulfate, 25 mg / L sodium selenite, L-lysine and vitamin B1. In terms of mass concentration, the ratio of sodium selenite, L-lysine and vitamin B1 is 1:(116-232):(0.06-0.12).

[0007] Furthermore, the components of the Candida utilis culture medium include 9.56 g / L yeast extract, 19.86 g / L glucose, 1.45 g / L dipotassium hydrogen phosphate, 1.12 g / L magnesium sulfate, 25 mg / L sodium selenite, L-lysine and vitamin B1. In terms of mass concentration, the ratio of sodium selenite, L-lysine and vitamin B1 is 1:232:0.12.

[0008] Furthermore, the Candida utilis is Candida utilis CICC 1769 (Beijing Yuwei Technology Co., Ltd.).

[0009] Furthermore, the Aspergillus niger is Aspergillus niger CICC 40084 (Beijing Yuwei Technology Co., Ltd.).

[0010] Furthermore, the Bacillus licheniformis is Bacillus licheniformis CICC 10095 (Beijing Yuwei Technology Co., Ltd.).

[0011] Furthermore, based on volume, the ratio of the bacterial solution of Candida utilis, the bacterial solution of Aspergillus niger, and the bacterial solution of Bacillus licheniformis is 1:1:1.

[0012] Furthermore, the nitrogen source includes ammonium sulfate.

[0013] Furthermore, the carbon source includes glucose.

[0014] Furthermore, the added amount of the leavening agent is 6% of the Hami melon by mass.

[0015] Furthermore, based on mass, the added mass of the carbon source is 5% of the Hami melon.

[0016] Furthermore, based on mass, the added mass of the nitrogen source is 2% of the Hami melon.

[0017] Furthermore, the fermentation conditions are: fermentation temperature is 36°C-38°C, and fermentation time is 24h-26h.

[0018] Furthermore, the drying temperature is 50°C-60°C.

[0019] Furthermore, those skilled in the art should understand that the purpose of pulverization is to refine the protein feed, and the technicians can adjust the particle size of the pulverized protein feed according to actual needs.

[0020] Furthermore, the conditions for culturing the Candida utilis in the Candida utilis culture medium include: culturing on a shaking platform at 30° C. for 16 hours.

[0021] Furthermore, the method for preparing the bacterial liquid of Aspergillus niger includes: inoculating Aspergillus niger in an Aspergillus niger culture medium, and the culture conditions include: culturing in a shaking table at a temperature of 35° C. for 48 hours.

[0022] Furthermore, the composition of the Aspergillus niger culture medium includes: 20 g / L peptone, 10 g / L yeast extract, 20 g / L glucose, a pH value of 6.5, and the balance deionized water.

[0023] Furthermore, the method for preparing the bacterial solution of Bacillus licheniformis includes: inoculating Bacillus licheniformis into a Bacillus licheniformis culture medium, and the culture conditions include: culturing in a shaking incubator at a temperature of 35° C. for 36 hours.

[0024] Furthermore, the composition of the Bacillus licheniformis culture medium includes: 10g / L peptone, 3g / L beef extract, 5g / L sodium chloride, 15g / L agar, pH value of 7, and the balance deionized water.

[0025] The invention also provides application of the method in producing selenium-enriched protein feed by fermenting Hami melon.

[0026] The embodiments of the present invention have the following technical effects: 1. In the present invention, Aspergillus niger can produce cellulase during its growth, and cellulase can decompose part of the cellulose in the Hami melon epidermis, which will degrade the crude fiber therein to a certain extent, thereby facilitating further improvement in the utilization of the fermentation substrate. Cellulase can hydrolyze a large amount of cellulose in the crushed Hami melon residue into monosaccharides, providing a carbon source for the fermentation process, further improving the utilization of the fermentation substrate, and Candida utilis can utilize nutrient sources such as monosaccharides and disaccharides during its growth, converting them into proteins, thereby increasing the protein content of the product. Bacillus licheniformis can not only increase the cell mass of Candida utilis through synergistic action, thereby facilitating conversion of carbohydrate substances into proteins, but also remove the peculiar smell of the fermentation product, thereby facilitating improvement in the quality of the final protein feed product.

[0027] 2. Selenium is one of the essential trace elements for the body and is vital to the body. It protects the body from damage by free radicals, participates in the detoxification of heavy metals, regulates the body's immune system, and is an important component of many proteins in the body, such as glutathione peroxidase, thioredoxin reductase, and iodinated thyronine deiodinase. During the cultivation process, Candida utilis can convert inorganic selenium into organic forms by combining it with macromolecules in the body through its own metabolic activities, which mainly exist in the form of selenoamino acids and selenoproteins, ultimately allowing selenium to exist in protein feed.

[0028] 3. When Candida utilis is used for selenium enrichment, excessive addition of sodium selenite will inhibit the growth of Candida utilis. As one of the main strains of Hami melon fermentation, the number of viable bacteria of Candida utilis after selenium enrichment is reduced; on the one hand, it is not conducive to the conversion of protein in the fermented Hami melon, resulting in a long fermentation cycle and a low protein conversion rate. On the other hand, the selenium-enriched content of Candida utilis is reduced, resulting in a reduction in the content of selenium in the final protein feed. Therefore, in the present invention, L-lysine and vitamin B1 are further added to the culture of Candida utilis. It is found that L-lysine and vitamin B1 can solve the situation of Candida utilis growth inhibition caused by sodium selenite. When the added mass concentration of sodium selenite in the culture medium is increased to 25 mg / L, the number of viable bacteria of Candida utilis can also be increased, which is not only beneficial to the Hami melon fermentation process, but also can increase the selenium content in the feed.

[0029] 4. In the present invention, Hami melon is used as a fermentation substrate. Hami melon has a high sugar content. During the fermentation process, the pH change of the fermentation environment will inhibit the activity of the fermentation agent. Therefore, it is necessary to accelerate the protein conversion rate to ensure that a high-protein feed is obtained in a shorter time, thereby avoiding the economic losses caused by long-term fermentation and the low protein conversion rate. Therefore, in the present invention, it is also necessary to ensure the activity and quantity of Candida utilis in the fermentation environment, so as to help quickly improve the protein conversion rate. Aspergillus niger and Bacillus licheniformis in the fermentation environment can promote the decomposition of Hami melon fiber into monosaccharides, which is conducive to the rapid metabolism of Candida utilis, thereby helping to improve the activity; when preparing the bacterial solution of Candida utilis, the added L-lysine and vitamin B1 can increase the number of viable bacteria of Candida utilis, thereby ensuring the number of viable bacteria of Candida utilis in the initial fermentation environment, which is further conducive to improving the protein conversion rate. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0031] In a first aspect, some embodiments of the present invention provide a method for producing selenium-rich protein feed by multi-bacteria cooperative fermentation of Hami melon, comprising the following steps: The cantaloupe is crushed, and then mixed with a carbon source and a nitrogen source, and then a fermentation agent is inoculated to ferment; the fermented product is dried and crushed to obtain a protein feed; The fermentation agent includes Candida utilis, Aspergillus niger, and Bacillus licheniformis; The method for preparing the bacterial liquid of Candida utilis comprises: culturing the Candida utilis in a Candida utilis culture medium, The components of the Candida utilis culture medium include 9.56 g / L yeast extract, 19.86 g / L glucose, 1.45 g / L potassium dihydrogen phosphate, 1.12 g / L magnesium sulfate, 25 mg / L sodium selenite, L-lysine and vitamin B1. In terms of mass concentration, the ratio of sodium selenite, L-lysine and vitamin B1 is 1:(116-232):(0.06-0.12).

[0032] In some embodiments, the ingredients of the Candida utilis culture medium include 9.56 g / L yeast extract, 19.86 g / L glucose, 1.45 g / L potassium dihydrogen phosphate, 1.12 g / L magnesium sulfate, 25 mg / L sodium selenite, L-lysine and vitamin B1. In terms of mass concentration, the ratio of sodium selenite, L-lysine and vitamin B1 is 1:232:0.12.

[0033] In some embodiments, the Candida utilis is Candida utilis CICC 1769 (Beijing Yuwei Technology Co., Ltd.).

[0034] In some embodiments, the Aspergillus niger is Aspergillus niger CICC 40084 (Beijing Yuwei Technology Co., Ltd.).

[0035] In some embodiments, the Bacillus licheniformis is Bacillus licheniformis CICC 10095 (Beijing Yuwei Technology Co., Ltd.).

[0036] In some embodiments, the ratio of the bacterial solution of Candida utilis, the bacterial solution of Aspergillus niger, and the bacterial solution of Bacillus licheniformis is 1:1:1 by volume.

[0037] In some embodiments, the nitrogen source includes ammonium sulfate.

[0038] In some embodiments, the carbon source comprises glucose.

[0039] In some embodiments, the added amount of the leavening agent is 6% of the Hami melon by mass.

[0040] In some embodiments, the added mass of the carbon source is 5% of the Hami melon by mass.

[0041] In some embodiments, the added amount of the nitrogen source is 2% of the Hami melon by mass.

[0042] In some embodiments, the fermentation conditions are: fermentation temperature is 36° C.-38° C., and fermentation time is 24 h-26 h.

[0043] In some embodiments, the drying temperature is 50°C-60°C.

[0044] In some embodiments, the culture conditions of the Candida utilis in the Candida utilis culture medium include: culturing in a shaking incubator at 30° C. for 16 hours.

[0045] In some embodiments, the method for preparing the Aspergillus niger bacterial liquid includes: inoculating Aspergillus niger in an Aspergillus niger culture medium, and the culture conditions include: culturing in a shaking table at a temperature of 35° C. for 48 hours.

[0046] In some embodiments, the composition of the Aspergillus niger culture medium includes: 20 g / L peptone, 10 g / L yeast extract, 20 g / L glucose, pH value is 6.5, and the balance is deionized water.

[0047] In some embodiments, the method for preparing the bacterial solution of Bacillus licheniformis includes: inoculating Bacillus licheniformis into a Bacillus licheniformis culture medium, and the culture conditions include: culturing in a shaking incubator at a temperature of 35° C. for 36 hours.

[0048] In some embodiments, the composition of the Bacillus licheniformis culture medium includes: 10 g / L peptone, 3 g / L beef extract, 5 g / L sodium chloride, 15 g / L agar, pH 7, and the balance deionized water.

[0049] In a second aspect, some embodiments of the present invention also provide the application of the method in producing selenium-rich protein feed by fermenting Hami melon.

[0050] The following is described in detail with reference to specific embodiments and comparative examples: (1) Preparation of Aspergillus niger culture liquid: In a liquid culture medium, add 20 g of peptone, 10 g of yeast extract, 20 g of glucose, and 1 L of distilled water, adjust the pH value of the culture medium to 6.5, and sterilize at 121°C for 20 min. Pick 1-2 rings of single colonies from the activated Aspergillus niger and inoculate them into the sterilized liquid culture medium. After culturing at 35°C and 160 r / min on a shaking table for 48 h, the Aspergillus niger culture liquid was obtained, wherein the Aspergillus niger was Aspergillus niger CICC 40084 (Beijing Yuwei Technology Co., Ltd.).

[0051] (2) Preparation of Bacillus licheniformis culture medium: In a liquid culture medium, add 10 g of peptone, 3 g of beef extract, 5 g of sodium chloride, 15 g of agar, and 1 L of distilled water. Adjust the pH value of the culture medium to 7.0 and sterilize at 121°C for 20 min. Pick 1-2 loops of single colonies of the activated Bacillus licheniformis and inoculate them into the sterilized liquid culture medium. After culturing at 35°C and 160 r / min on a shaking table for 36 h, the Bacillus licheniformis culture medium was obtained, wherein the Bacillus licheniformis was Bacillus licheniformis CICC 10095 (Beijing Yuwei Technology Co., Ltd.).

[0052] Embodiment 1: Preparation of the bacterial liquid of Candida utilis: in a liquid culture medium, 9.56g of yeast extract, 19.86g of glucose, 1.45g of potassium hydrogen phosphate, 1.12g of magnesium sulfate, 25mg of sodium selenite, 2.9g of L-lysine, 1.5mg of vitamin B1, and 1L of distilled water, adjust the pH value of the culture medium to 7.0, sterilize at 121°C for 20min, pick 1-2 rings of single colonies of the activated Candida utilis and inoculate them into the sterilized liquid culture medium. After culturing at 30°C and 160r / min shaking for 16h, the bacterial liquid of Candida utilis was obtained; wherein, the Candida utilis was Candida utilis CICC 1769 (Beijing Yuwei Technology Co., Ltd.).

[0053] Weigh 500g of the washed Hami melon and put it into the pulper. Stir appropriately during the pulping process to ensure the smoothness and uniformity of the pulping process. The pulping time is preferably about 5 minutes. Add a certain carbon source according to the weight of the Hami melon, the addition amount is 5%, that is, 25g of glucose. Add a certain nitrogen source according to the weight of the Hami melon, the addition amount is 2%, that is, 10g of ammonium sulfate. Mix the bacterial liquid of Candida utilis, the bacterial liquid of Aspergillus niger and the bacterial liquid of Bacillus licheniformis in a volume ratio of 1:1:1. The mixed bacterial liquid is inoculated as a starter, and the inoculation amount is 6% of the weight of the Hami melon, a total of 30mL of bacterial liquid, placed in a sterile fermentation tank at 36℃ for fermentation treatment, and the reducing sugar content after fermentation is tested. When the reducing sugar content reaches equilibrium, the fermentation is over. After the fermentation is over, the fermentation product is dried at 55℃, then crushed and passed through a 20-mesh molecular sieve.

[0054] Embodiment 2: The preparation method is the same as that of Example 1, but in Example 2, when preparing the bacterial solution of Candida utilis, 25 mg of sodium selenite, 5.8 g of L-lysine and 3 mg of vitamin B1 are used, and the rest is the same as that of Example 1.

[0055] Comparative Example 1: The preparation method is the same as that of Example 1, but in Comparative Example 1, when preparing the bacterial solution of Candida utilis, L-lysine and vitamin B1 are not added, and the rest are the same as those of Example 1.

[0056] Comparative Example 2: The preparation method is the same as that of Example 1, but in Comparative Example 2, L-lysine is not added when preparing the bacterial solution of Candida utilis, and the rest is the same as that of Example 1.

[0057] Comparative Example 3: The preparation method is the same as that of Example 1, but in Comparative Example 3, when preparing the bacterial solution of Candida utilis, vitamin B1 is not added, and the rest is the same as that of Example 1.

[0058] Comparative Example 4: The preparation method is the same as that of Example 1, but in Comparative Example 4, when preparing the bacterial solution of Candida utilis, 25 mg of sodium selenite, 1.45 g of L-lysine and 0.75 mg of vitamin B1 are used, and the rest are the same as those of Example 1.

[0059] Comparative Example 5: The preparation method is the same as that of Example 1, but in Comparative Example 5, 25 mg of sodium selenite, 8.7 g of L-lysine and 4.5 g of vitamin B1 are used in the preparation of the bacterial solution of Candida utilis, and the rest are the same as those of Example 1.

[0060] Comparative Example 6: In the liquid culture medium, 9.56g of yeast extract, 19.86g of glucose, 1.45g of potassium hydrogen phosphate, 1.12g of magnesium sulfate, and 1L of distilled water were added. The pH value of the culture medium was adjusted to 7.0, and sterilized at 121°C for 20min. 1-2 loops of single colonies of the activated Candida utilis were picked and inoculated into the sterilized liquid culture medium. After culturing at 30°C and 160r / min shaking for 16h, the bacterial liquid of Candida utilis was obtained.

[0061] The embodiments and comparative examples of the present invention were tested: (1) Test method for crude protein content: weigh about 0.5g of sample into a digestion tube, add 0.2g of copper sulfate and 3g of potassium sulfate, 10mL of concentrated sulfuric acid, place the digestion tube rack on a graphite digestion furnace, cover with a waste cover, select the curve heating process during the digestion process, and set the heating program to: 180℃ heating for 30min, 320℃ heating for 30min, 420℃ heating for 60min. After digestion is completed, cool to room temperature and use a K9860 fully automatic Kjeldahl nitrogen analyzer for determination.

[0062] (2) Test method for reducing sugar content: Take 0mL, 0.2mL, 0.4mL, 0.6mL, 0.8mL, and 1mL of glucose standard solution (1mg / mL) in 25mL test tubes, accurately add 2mL of 3,5-dinitrosalicylic acid reagent, heat in a boiling water bath for 2min, cool in running water, and fill to 15mL mark with water. Measure OD under UV spectrophotometer. 540 , glucose concentration is y, OD value is x, draw a standard curve; Take 10g of Hami melon homogenate, rinse with water into a 250mL volumetric flask, then add 3mL of potassium ferrocyanide and zinc acetate, and dilute to 250mL; take 30mL of the sample solution after distillation for centrifugation, and take the supernatant; take 10mL of the supernatant and dilute to a 100mL volumetric flask; take 1mL of the supernatant after distillation into a 10mL stoppered test tube, add water to 2mL, then add 4mL of 3,5-dinitrosalicylic acid and heat in a boiling water bath for 5min, cool to room temperature, dilute to volume and shake well, and measure OD 540 , and then bring it into the standard curve to calculate the content of reducing sugar.

[0063] (3) Method for determining the number of effective viable bacteria: Take 1 g of fermentation product and shake it in 9 mL of sterile water. Then dilute it step by step to an appropriate multiple and count it using the plate count method. The result is the number of viable bacteria per gram of wet basis.

[0064] (4) Testing method for selenium content in feed: Accurately weigh 0.5g (accurate to 0.001g) of solid sample, place in a conical flask, add 10mL nitric acid-perchloric acid mixture (9+1) and a few glass beads, cover with a watch glass and digest overnight. Heat on a hot plate the next day and add nitric acid in time. When the solution becomes clear and colorless with white smoke, continue to heat until the remaining volume is about 2mL. Do not evaporate to dryness. After cooling, add 5mL of hydrochloric acid solution (6mol / L), continue to heat until the solution becomes clear and colorless with white smoke, continue to heat until the remaining volume is about 2mL, and cool. At the same time, make a reagent blank.

[0065] Preparation of standard curve: Selenium standard series solutions were placed on the machine in order of mass from low to high to measure the fluorescence intensity of 4,5-benzoselenone. The standard curve was prepared with mass as the horizontal axis and fluorescence intensity as the vertical axis.

[0066] Add hydrochloric acid solution (1+9) to the digested sample solution and blank solution to 5 mL, then add 20 mL of DTA mixed solution, and adjust to light reddish orange (pH 1.5-2.0) with ammonia solution (1+1) and hydrochloric acid solution (1+9). The following steps are performed in a dark room: add 3 mL of DAN reagent (1g / L), mix well, heat in a boiling water bath for 5 minutes, take out and cool, add 3 mL of cyclohexane, shake for 4 minutes, transfer all the solution into a separatory funnel, discard the water layer after stratification, carefully pour the cyclohexane layer from the upper opening of the separatory funnel into a test tube with a lid, and measure using a fluorescence spectrophotometer. The reference conditions of the fluorescence spectrophotometer are: excitation light wavelength 376 nm, emission light wavelength 520 nm.

[0067] Results and Analysis: Table 1 Test results of embodiments and comparative examples

[0068] The protein content of Hami melon before fermentation is 5.25%. The protein content of Hami melon fermentation product obtained by the method of the present invention is not less than 23%, and the protein content is increased by at least 4 times by the method of the present invention. It can be seen that Hami melon is successfully prepared into protein feed by the method of the present invention. And the selenium content in the feed obtained by the present invention is not less than 0.43 mg / kg.

[0069] In the present invention, by comparing Example 1-Example 2 with Comparative Example 1-Comparative Example 5, it is found that the method of the present invention not only successfully increases the number of viable bacteria of Candida utilis, but also reduces the time of fermenting Hami melon and improves the conversion rate of crude protein in the feed.

[0070] In the process of fermenting Hami melon, Hami melon is used as the fermentation substrate. Hami melon has a high sugar content. During the fermentation process, the pH change of the fermentation environment will inhibit the activity of the fermentation agent. Therefore, it is necessary to speed up the protein conversion rate to ensure that protein feed is obtained in a shorter time, so as to avoid the economic loss and low protein conversion rate caused by long-term fermentation. The method of improving the protein conversion rate, on the one hand, needs to ensure the mutual cooperation between the fermentation agents. The Aspergillus niger in the fermentation agent can produce cellulase during the growth process, and the cellulase can decompose part of the cellulose in the Hami melon epidermis to form monosaccharides and disaccharides, which can be quickly used by Candida utilis. Bacillus licheniformis can not only increase the amount of Candida utilis through synergistic action, but also the interaction between the flora promotes the increase of the number of live bacteria of Candida utilis in the fermentation environment, which is conducive to improving the rapid conversion of protein; on the other hand, it is necessary to ensure that the number of live bacteria of Candida utilis inoculated in the fermentation environment is more, so that the basic number of live bacteria in the fermentation environment can be more, which is also conducive to improving the protein conversion process.

[0071] Therefore, further comparison of Example 1-Example 2 with Comparative Example 6 found that after adding sodium selenite, the number of viable bacteria of Candida utilis decreased significantly. It can be seen that when Candida utilis is used for selenium enrichment, excessive addition of sodium selenite will cause the growth of Candida utilis to be inhibited. Further study of Example 1-Example 2 and Comparative Example 1-Comparative Example 3 found that when L-lysine and vitamin B1 were added during the selenium enrichment process of Candida utilis, L-lysine and vitamin B1 could solve the situation of inhibited growth of Candida utilis caused by sodium selenite. It can be seen that in the process of selenium enrichment of Candida utilis, by adding L-lysine and vitamin B1, not only the number of viable bacteria of Candida utilis can be increased, but also the selenium content in the feed can be increased. Therefore, it is further preferred that, in the Candida utilis culture medium, the ratio of sodium selenite, L-lysine and vitamin B1 is 1:(116-232):(0.06-0.12) in terms of mass concentration.

[0072] On this basis, further comparisons were made between Example 1-Example 2 and Comparative Example 4-Comparative Example 5, and it was found that Example 1-Example 2 was significantly better than Comparative Example 4-Comparative Example 5, and Example 2 was the best. It may be because the addition of L-lysine and vitamin B1 will affect the metabolic pathway of Candida utilis. When the addition amount is small, the protection ability of Candida utilis may be weak, so the number of viable bacteria of Candida utilis is less than that of Example 1-Example 2; and when the addition amount of L-lysine and vitamin B1 is more, other metabolic pathways may be affected, thereby causing a decrease in the number of viable bacteria of Candida utilis. Therefore, it is further preferred that in the Candida utilis culture medium, the ratio of sodium selenite, L-lysine and vitamin B1 is 1:232:0.12 in terms of mass concentration.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing selenium-rich protein feed by multi-bacteria cooperative fermentation of Hami melon, characterized in that: The steps include: The cantaloupe is crushed, and then mixed with a carbon source and a nitrogen source, and then a fermentation agent is inoculated to ferment; the fermented product is dried and crushed to obtain a protein feed; The fermentation agent includes Candida utilis, Aspergillus niger, and Bacillus licheniformis; The method for preparing the bacterial liquid of Candida utilis comprises: culturing the Candida utilis in a Candida utilis culture medium, The components of the Candida utilis culture medium include 9.56 g / L yeast extract, 19.86 g / L glucose, 1.45 g / L potassium dihydrogen phosphate, 1.12 g / L magnesium sulfate, 25 mg / L sodium selenite, L-lysine and vitamin B1. In terms of mass concentration, the ratio of sodium selenite, L-lysine and vitamin B1 is 1:(116-232):(0.06-0.12).

2. The method according to claim 1, characterized in that In terms of volume, the ratio of the bacterial solution of Candida utilis, the bacterial solution of Aspergillus niger, and the bacterial solution of Bacillus licheniformis is 1:1:

1.

3. The method according to claim 1, characterized in that The nitrogen source includes ammonium sulfate; the carbon source includes glucose.

4. The method according to claim 1, characterized in that: In terms of mass, the added mass of the leavening agent is 6% of the Hami melon.

5. The method according to claim 1, characterized in that In terms of mass, the added mass of the carbon source is 5% of the Hami melon.

6. The method according to claim 1, characterized in that In terms of mass, the added mass of the nitrogen source is 2% of the Hami melon.

7. The method according to claim 1, characterized in that The fermentation conditions are as follows: fermentation temperature is 36°C-38°C, and fermentation time is 24h-26h.

8. The method according to claim 1, characterized in that The drying temperature is 50°C-60°C.

9. The method according to claim 1, characterized in that: The conditions for culturing the Candida utilis in the Candida utilis culture medium include: culturing on a shaking platform at 30° C. for 16 hours.

10. Use of the method according to any one of claims 1 to 9 in producing selenium-enriched protein feed by fermenting Hami melon.

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