Protein-based microcapsule, preparation method and prepared pig feed

Abstract

The invention discloses a protein-based microcapsule, a preparation method and a prepared pig feed, and belongs to the field of livestock and poultry feeds, the protein-based microcapsule comprises a core material and a wall material, the core material comprises a complex microbial inoculant, a plant extract and a protein-based film coating agent, and the wall material comprises whey protein and sodium caseinate; the complex microbial inoculants comprise clostridium butyricum and lactobacillus plantarum; the plant extract comprises astragalus polysaccharide and a folium cortex eucommiae extract; the protein-based film coating agent comprises whey protein, zein and modified soybean protein isolate; the modified soybean protein isolate is subjected to phosphorylation modification. According to the invention, the protein-based film coating agent is used for primarily coating the complex microbial inoculant and the plant extract to form the core material, and then the core material and the protein-based wall material are cooperated to construct a dual-protection system, so that the complex microbial inoculant can safely reach the intestinal colonization site, and nutrition and immune support can be provided for the colonization process.

Description

Technical Field

[0001] This invention relates to the field of livestock and poultry feed, and particularly to a protein-based microcapsule, its preparation method, and the prepared pig feed. Background Technology

[0002] In modern pig farming, maintaining animal gut health is a key element in achieving efficient and sustainable development. Probiotics, as live microorganisms that exert beneficial effects by improving the balance of the host's gut microbiota, have gained widespread recognition for their potential in replacing antibiotics, enhancing immunity, and improving feed conversion rates. However, directly applying probiotics to pig feed faces a series of severe technical challenges, which significantly restrict the stability and economic viability of their practical application.

[0003] Most probiotic strains exhibit poor stability during feed processing, storage, and transportation. Conventional feed pelleting processes involve high temperatures and pressures, which can be fatal to exposed probiotics. Furthermore, even with simple room temperature storage, the activity of the bacteria will irreversibly decline over time, resulting in a live bacteria count far below the design standard when the product is fed.

[0004] Furthermore, the complex digestive environment of pigs constitutes a significant barrier to the colonization of probiotics. The highly acidic environment of the stomach and pepsin can rapidly inactivate a large number of unprotected bacteria. Subsequently, the high concentration of bile salts in the anterior small intestine has a strong dissolving and destructive effect on bacterial cell membranes. This series of rigorous digestive processes means that the proportion of orally ingested probiotics that ultimately survive and reach the posterior intestinal tract for colonization is extremely low, often less than one percent. This significant loss of live bacteria makes it difficult for probiotics to fully realize their theoretical functions.

[0005] Currently, existing microencapsulation techniques for protecting probiotics include microcapsule structures with a single wall material. However, these often suffer from insufficient bonding strength and biocompatibility between the core and wall materials, potentially leading to premature disintegration in the gastrointestinal environment and failing to provide effective tiered protection. Other methods utilize synthetic polymers as encapsulation materials to enhance stability, but these materials are often expensive and not as safe as natural ingredients.

[0006] Therefore, developing a probiotic encapsulation technology based on natural raw materials that combines excellent processing stability, gastrointestinal targeted release, and good biocompatibility has become an urgent need for the pig farming and feed industries. Summary of the Invention

[0007] The purpose of this invention is to provide a protein-based microcapsule to solve the problems of poor stability and difficulty in full absorption of probiotics during feed processing, storage and transportation in the prior art.

[0008] The present invention also aims to provide a method for preparing protein-based microcapsules.

[0009] Another objective of this invention is to provide an application of protein-based microcapsules in pig feed.

[0010] In a first aspect, the present invention provides a protein-based microcapsule, comprising a core material and a wall material, wherein the core material is a composite microbial agent, a plant extract and a protein-based coating agent, and the wall material is whey protein and sodium caseinate. The compound microbial agent includes Clostridium butyricum and Lactobacillus plantarum; Plant extracts include astragalus polysaccharide and eucommia leaf extract; Protein-based coating agents include whey protein, zein, and modified soy protein isolate; The modified soy protein isolate is phosphorylated.

[0011] By adopting the above technical solutions, the protein-based coating agent initially encapsulates the compound microbial agent and plant extracts to form a core material, which then works synergistically with the protein-based wall material to construct a dual protection system. This not only ensures that the compound microbial agent safely reaches the intestinal colonization site, but also provides nutritional and immune support for the colonization process.

[0012] Specifically, the core material includes a compound microbial agent, plant extracts, and a protein-based coating agent. The compound microbial agent contains Clostridium butyricum and Lactobacillus plantarum, which work synergistically. Butyric acid produced by Clostridium butyricum is a key energy source for pig intestinal epithelial cells and can effectively repair and enhance intestinal barrier function. Lactobacillus plantarum, on the other hand, effectively inhibits the growth of pathogenic bacteria in the intestine by rapidly producing acid. The combination of the two optimizes the intestinal microecological environment of pigs. Astragalus polysaccharides from plant extracts can activate the body's immune system and enhance non-specific immunity in pigs; while Eucommia ulmoides leaf extract has anti-inflammatory and antioxidant activities, which can relieve intestinal stress and synergistically promote intestinal health with probiotics. The protein-based coating agents include whey protein, zein, and modified soy protein isolate. Whey protein has excellent emulsifying and film-forming properties, enabling it to uniformly encapsulate the components of the compound microbial agent and plant extracts. Zein is insoluble in water and can form a hydrophobic layer on the core material surface, thereby blocking the invasion of gastric acid and water. The modified soy protein isolate is a phosphorylated modified soy protein isolate. The phosphate groups introduced into its molecules can crosslink with whey protein, sodium caseinate, and other components in the wall material through ionic bonds, significantly enhancing the binding capacity between the core material and the wall material, thereby improving the overall structural stability of the microcapsules. On the other hand, it can also ionize in the intestinal environment, generating a pH-responsive effect, promoting the targeted disintegration of the microcapsules and the precise release of probiotics, while providing a usable phosphorus source for the early colonization of probiotics.

[0013] The wall material consists of whey protein and sodium caseinate, both of which possess excellent film-forming and thermogelling properties, forming a dense, continuous, and robust outer protective film during spray drying. This wall material structure effectively resists the high temperature, high pressure, and erosion from strong stomach acid and pepsin during feed pelleting, ensuring the safe passage of the core material through the stomach and achieving efficient delivery of probiotics.

[0014] Preferably, the ratio of effective viable bacteria counts of Clostridium butyricum to Lactobacillus plantarum in the compound microbial agent is (1-2):(1-2), and the total effective viable bacteria count of the compound microbial agent is not less than 1.0 × 10⁻⁶. 10 CFU / g.

[0015] Preferably, the mass ratio of Astragalus polysaccharide to Eucommia ulmoides leaf extract in the plant extract is 1:(3-4); and the mass ratio of whey protein to sodium caseinate in the wall material is 1:(1-2).

[0016] Preferably, the mass ratio of whey protein, zein, and modified soy protein isolate in the protein-based coating agent is 1:(1-2):(2-3).

[0017] Preferably, the modified soy protein isolate is obtained by the following preparation method: Soy protein isolate is dispersed in deionized water, phosphorylation reagent is added, pH is adjusted to 7-9, and the reaction is carried out at 30-50℃ for 2-4 hours. After that, the pH is adjusted to 3-6, and the product is obtained by centrifugation and drying.

[0018] Preferably, the mass ratio of soy protein isolate to phosphorylation reagent is 1:(0.01-0.1); the phosphorylation reagent includes one or more of sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, and sodium trimetaphosphate.

[0019] Secondly, the present invention provides a method for preparing protein-based microcapsules, comprising the following steps: S1. A compound bacterial agent is prepared by mixing Clostridium butyricum and Lactobacillus plantarum. A protein-based coating agent is prepared by mixing whey protein, zein and modified soy protein isolate. S2. Add the compound microbial agent, protein-based coating agent and plant extract to the mixer, mix evenly and then make the core material. S3. Add the core material and wall material to the mixer, mix them evenly, and then spray dry to obtain the final product.

[0020] Preferably, the mass ratio of the compound microbial agent, protein-based coating agent and plant extract is 1:(1.5-3):(0.3-2); the mass ratio of the core material and the wall material is 1:(1-3).

[0021] Preferably, in step S3, the mixing time is 0.5 to 1 hour; the spray drying parameters are: inlet temperature of 120 to 135°C, outlet temperature of 45 to 55°C, and feed peristaltic pump speed of 100 to 300 r / min.

[0022] Thirdly, the present invention also provides the application of any of the above-mentioned protein-based microcapsules in pig feed.

[0023] The beneficial effects of this invention are: 1. The protein-based microcapsules provided by this invention construct a dual protection system through the synergistic effect of protein-based coating agents and protein-based wall materials. This system not only ensures that the compound bacterial agent and plant extracts safely reach the intestinal colonization site, but also provides further nutritional and immune support for the colonization process. This significantly improves the survival rate of probiotics during in vivo transport and after colonization, while also allowing for long-term preservation in a room-temperature external environment.

[0024] 2. The protein-based microcapsules provided by the present invention have a combination of compound microbial agents that can synergistically optimize the intestinal flora, with Clostridium butyricum repairing the intestinal wall and Lactobacillus plantarum inhibiting pathogens, thus jointly promoting intestinal health.

[0025] 3. The protein-based microcapsules provided by this invention, by adding astragalus polysaccharide and eucommia leaf extract, work synergistically with probiotics to promote growth while effectively enhancing the immunity and stress resistance of pigs.

[0026] 4. The protein-based microcapsules provided by the present invention have modified soy protein isolate in their protein-based coating agent by phosphorylation modification, which introduces phosphate groups. On the one hand, this enhances the binding force between the core material and the wall material and improves the stability of the microcapsules. On the other hand, it endows the microcapsules with pH-responsive release characteristics and can provide a phosphorus source for probiotic colonization.

[0027] 5. The protein-based microcapsules provided by this invention use whey protein and sodium caseinate as wall materials, both of which are natural proteins, safe and harmless, and can form a dense protective layer, effectively resisting the harsh environment of feed processing and the gastrointestinal tract, thus achieving highly efficient protection of all-natural components. Detailed Implementation

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0029] A protein-based microcapsule includes a core material and a wall material. The core material is a compound microbial agent, plant extracts and a protein-based coating agent, and the wall material is whey protein and sodium caseinate. The compound microbial agent includes Clostridium butyricum and Lactobacillus plantarum; Plant extracts include astragalus polysaccharide and eucommia leaf extract; Protein-based coating agents include whey protein, zein, and modified soy protein isolate; The modified soy protein isolate is phosphorylated.

[0030] By adopting the above technical solutions, the protein-based coating agent initially encapsulates the compound microbial agent and plant extracts to form a core material, which then works synergistically with the protein-based wall material to construct a dual protection system. This not only ensures that the compound microbial agent safely reaches the intestinal colonization site, but also provides nutritional and immune support for the colonization process.

[0031] Specifically, the core material includes a compound microbial agent, plant extracts, and a protein-based coating agent. The compound microbial agent contains Clostridium butyricum and Lactobacillus plantarum, which work synergistically. Butyric acid produced by Clostridium butyricum is a key energy source for pig intestinal epithelial cells and can effectively repair and enhance intestinal barrier function. Lactobacillus plantarum, on the other hand, effectively inhibits the growth of pathogenic bacteria in the intestine by rapidly producing acid. The combination of the two optimizes the intestinal microecological environment of pigs. Astragalus polysaccharides from plant extracts can activate the body's immune system and enhance non-specific immunity in pigs; while Eucommia ulmoides leaf extract has anti-inflammatory and antioxidant activities, which can relieve intestinal stress and synergistically promote intestinal health with probiotics. The protein-based coating agents include whey protein, zein, and modified soy protein isolate. Whey protein has excellent emulsifying and film-forming properties, enabling it to uniformly encapsulate the components of the compound microbial agent and plant extracts. Zein is insoluble in water and can form a hydrophobic layer on the core material surface, thereby blocking the invasion of gastric acid and water. The modified soy protein isolate is a phosphorylated modified soy protein isolate. The phosphate groups introduced into its molecules can crosslink with whey protein, sodium caseinate, and other components in the wall material through ionic bonds, significantly enhancing the binding capacity between the core material and the wall material, thereby improving the overall structural stability of the microcapsules. On the other hand, it can also ionize in the intestinal environment, generating a pH-responsive effect, promoting the targeted disintegration of the microcapsules and the precise release of probiotics, while providing a usable phosphorus source for the early colonization of probiotics.

[0032] The wall material consists of whey protein and sodium caseinate, both of which possess excellent film-forming and thermogelling properties, forming a dense, continuous, and robust outer protective film during spray drying. This wall material structure effectively resists the high temperature, high pressure, and erosion from the strong acid and pepsin in the stomach during feed pelleting, ensuring the safe passage of the core material through the stomach and enabling efficient delivery of probiotics.

[0033] In some embodiments, the effective viable count ratio of Clostridium butyricum to Lactobacillus plantarum in the compound microbial agent is (1-2):(1-2), and the total effective viable count of the compound microbial agent is not less than 1.0 × 10⁻⁶. 10CFU / g; This live bacteria ratio ensures the synergistic effect of the two probiotics in the gut: Clostridium butyricum is responsible for repairing the intestinal wall and producing butyric acid, while Lactobacillus plantarum is responsible for inhibiting pathogens and maintaining an acidic environment, thereby optimizing the balance of intestinal flora; the total effective live bacteria count is not less than 1.0 × 10⁻⁶. 10 CFU / g ensures that even if some loss occurs during processing and storage, the final feeding dose will still reach an effective level and exert its probiotic function.

[0034] In some embodiments, the mass ratio of Astragalus polysaccharide to Eucommia ulmoides leaf extract in the plant extract is 1:(3-4); the mass ratio of whey protein to sodium caseinate in the wall material is 1:(1-2); the mass ratio of Astragalus polysaccharide to Eucommia ulmoides leaf extract is based on the synergistic effect of their immune-enhancing and anti-inflammatory activities, and a higher proportion of Eucommia ulmoides leaf extract can better alleviate intestinal inflammation and oxidative stress; the mass ratio of whey protein to sodium caseinate in the wall material optimizes film-forming properties and thermal stability, whey protein provides flexibility, and sodium caseinate enhances structural strength, and the two combine to form a uniform and dense protective layer.

[0035] In some embodiments, the mass ratio of whey protein, zein, and modified soy protein isolate in the protein-based coating agent is 1:(1-2):(2-3); this ratio ensures that the coating agent has good emulsifying, hydrophobic, and cross-linking properties. Whey protein serves as the basic film-forming material, zein provides a hydrophobic barrier, and modified soy protein isolate enhances its binding with the wall material through phosphorylation and achieves pH-responsive release. The three components synergistically improve the stability and targeting of the core material.

[0036] In some embodiments, modified soy protein isolate is obtained by the following preparation method: Soy protein isolate is dispersed in deionized water, phosphorylation reagent is added, pH is adjusted to 7-9, and the reaction is carried out at 30-50℃ for 2-4 hours. After that, the pH is adjusted to 3-6, and the product is obtained by centrifugation and drying.

[0037] Phosphorylation modification of soy protein isolate introduces phosphate groups, enhancing the protein's hydrophilicity and ionic cross-linking ability. The phosphorylation reaction proceeds under weakly alkaline conditions, which favors the formation of phosphate ester bonds; the reaction is terminated by adjusting the pH to acidic conditions.

[0038] In some embodiments, the mass ratio of soy protein isolate to phosphorylation reagent is 1:(0.01 to 0.1); the phosphorylation reagent includes one or more of sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, and sodium trimetaphosphate; selecting a mass ratio of 1:(0.01 to 0.1) of soy protein isolate and phosphorylation reagent can balance the degree of phosphorylation and the risk of protein denaturation. Too low a ratio may lead to insufficient modification, while too high a ratio may cause excessive cross-linking or precipitation of the protein.

[0039] A method for preparing protein-based microcapsules includes the following steps: S1. A compound bacterial agent is prepared by mixing Clostridium butyricum and Lactobacillus plantarum. A protein-based coating agent is prepared by mixing whey protein, zein and modified soy protein isolate. S2. Add the compound microbial agent, protein-based coating agent and plant extract to the mixer, mix evenly and then make the core material. S3. Add the core material and wall material to the mixer, mix them evenly, and then spray dry to obtain the final product.

[0040] First, a compound bacterial agent and a protein-based coating agent are prepared by mixing. Then, this mixture is combined with plant extracts to prepare a core material. Finally, the core material and wall material are spray-dried to form microcapsules. This method is simple to operate, easy to scale up for production, and spray drying can quickly form microcapsules, reducing heat damage to probiotics.

[0041] In some embodiments, the mass ratio of the compound microbial agent, the protein-based coating agent, and the plant extract is 1:(1.5-3):(0.3-2); this mass ratio ensures that the probiotics and plant extracts in the core material are fully coated, while the protein-based coating agent provides a sufficient protective layer.

[0042] In some embodiments, the mass ratio of the core material to the wall material is 1:(1-3); this mass ratio ensures that the wall material forms a complete outer protective film while avoiding excessive wall material thickness that could affect intestinal release.

[0043] In some embodiments, in step S3, the mixing time is 0.5 to 1 hour; the spray drying parameters are an inlet temperature of 120 to 135°C, an outlet temperature of 45 to 55°C, and a feed peristaltic pump speed of 100 to 300 r / min; by adopting the above parameters, it can be ensured that the microcapsules are rapidly formed during the drying process, while minimizing the impact of high temperature on the activity of probiotics.

[0044] The application of any of the above-mentioned protein-based microcapsules in pig feed: The protein-based microcapsules prepared by this invention can be used in pig feed, granulated after uniform mixing, or fed directly. Microcapsules can effectively protect the stability of probiotics and plant extracts during feed processing and storage, improve pig intestinal health, immunity, and feed conversion rate, while reducing antibiotic use.

[0045] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0046] Preparation Example

[0047] Preparation Example 1: A modified soy protein isolate, comprising the following steps: Soy protein isolate was dispersed in deionized water to prepare a suspension with a mass fraction of 8%. 5% sodium tripolyphosphate was added, and 0.1M sodium hydroxide was added to adjust the pH of the suspension to 7.5. The mixture was reacted at 40℃ for 3 hours. Then, the pH of the solution was adjusted to 4 with 0.1M hydrochloric acid. After centrifugation and drying, a modified soy protein isolate was obtained.

[0048] Example

[0049] Example 1, a protein-based microcapsule, comprising the following steps: S1. A compound bacterial agent is prepared by mixing Clostridium butyricum and Lactobacillus plantarum. A protein-based coating agent is prepared by mixing whey protein, zein and modified soy protein isolate. S2. By weight, add 1 part of compound microbial agent, 2 parts of protein-based coating agent and 1 part of plant extract to a mixer and stir at 600 rpm for 1 hour to make core material. S3. Add 10 parts of core material and 20 parts of wall material to a mixer, mix evenly, and then spray dry under the conditions of inlet air temperature of 125℃, peristaltic pump speed of 300r / min, and outlet air temperature of 50℃ to obtain protein-based microcapsules. The effective viable bacteria count of the compound microbial agent is 3×10⁻⁶. 10 CFU / g, the effective live bacteria ratio of Clostridium butyricum to Lactobacillus plantarum is 1:2; The mass ratio of Astragalus polysaccharide to Eucommia ulmoides leaf extract in the plant extract is 1:3; The mass ratio of whey protein, zein, and modified soy protein isolate prepared in Preparation Example 1 in the protein-based coating agent is 1:1:2; The mass ratio of whey protein to sodium caseinate in the wall material is 1:1.

[0050] Example 2, a protein-based microcapsule, differs from Example 1 only in that the mass ratio of whey protein, zein, and modified soy protein isolate prepared in Example 1 in the protein-based coating agent is 1:2:3.

[0051] Example 3: A protein-based microcapsule, which differs from Example 1 only in that the amount of protein-based coating agent added in step S2 is 1 part.

[0052] Comparative Example

[0053] Comparative Example 1: A protein-based microcapsule, differing from Example 1 only in that the modified soy protein isolate in the example was replaced with the same mass of soy protein isolate.

[0054] Comparative Example 2, a protein-based microcapsule, comprising the following steps: S1. A compound bacterial agent is prepared by mixing Clostridium butyricum and Lactobacillus plantarum. A protein-based coating agent is prepared by mixing whey protein, zein and modified soy protein isolate. S2. By weight, add 1 part of compound microbial agent, 2 parts of protein-based coating agent and 1 part of plant extract to a mixer and stir at 600 rpm for 1 hour to make core material. S3. Add 10 portions of core material to a mixer, mix evenly, and then spray dry under the conditions of an inlet air temperature of 125℃, a peristaltic pump speed of 300r / min, and an outlet air temperature of 50℃ to obtain protein-based microcapsules. The effective viable bacteria count of the compound microbial agent is 3×10⁻⁶. 10 CFU / g, the effective live bacteria ratio of Clostridium butyricum to Lactobacillus plantarum is 1:2; The mass ratio of Astragalus polysaccharide to Eucommia ulmoides leaf extract in the plant extract is 1:3; The mass ratio of whey protein, zein, and modified soy protein isolate prepared in Example 1 in the protein-based coating agent is 1:1:2.

[0055] Application examples

[0056] Application Example 1: A protein-based microcapsule pig feed. Three parts of the protein-based microcapsules prepared in Example 1, 15 parts of soybean meal, 10 parts of fish meal, 10 parts of corn flour, 1 part of (NH4)2SO4, 0.5 parts of compound vitamins, and 0.5 parts of compound minerals were mixed evenly, pulverized and passed through an 80-mesh sieve, and then granulated to obtain a protein-based microcapsule pig feed.

[0057] Application Example 2 is a protein-based microcapsule pig feed, which differs from Application Example 1 only in that the protein-based microcapsules prepared in Comparative Example 1 are replaced with the same mass of protein-based microcapsules prepared in Comparative Example 1.

[0058] Application Example 3 is a protein-based microcapsule pig feed, which differs from Application Example 1 only in that the protein-based microcapsules prepared by Comparative Example 2 of the same mass are used to replace the protein-based microcapsules of Application Example 1.

[0059] Performance testing

[0060] 1. Viable cell count test: The viable cell count of the protein-based microcapsules prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested by plate counting method; 2. Simulated small intestinal digestion fluid test: The protein-based microcapsules prepared in Examples 1-3 and Comparative Examples 1-2 were added to artificial small intestinal fluid. The small intestinal digestion process was simulated under anaerobic conditions of 37℃ and 90 r / min. After 3 hours, samples were taken and the viable bacteria count in the protein-based microcapsules was calculated. The artificial small intestinal fluid was prepared according to the Chinese Pharmacopoeia. The specific method was as follows: 6.8 g of potassium dihydrogen phosphate was dissolved in 500 mL of water, and the pH was adjusted to 6.8 with 0.1 mol / L sodium hydroxide solution. 10 g of trypsin was dissolved in an appropriate amount of water. The two solutions were mixed and diluted with water to 1000 mL. The test results are shown in Table 1. 3. Piglet growth performance test: 120 weaned piglets aged 30 days were randomly divided into 4 groups of 30 piglets each, with 3 experimental groups and 1 control group.

[0061] The experimental group used the protein-based microcapsule pig feed prepared in Application Examples 1-3, while the control group used a basal diet without any treatment. The experiment lasted 21 days. During the experiment, the piglets' feeding behavior was observed daily, and their initial weight was recorded before the experiment and their final initial weight was recorded after the experiment. The results are shown in Table 2. Table 1

[0062] According to Table 1, and in conjunction with Examples 1-3 and Comparative Examples 1-2, the viable bacterial count of the protein-based microcapsules in Comparative Examples 1-2 after small intestinal digestion was significantly lower than that in the examples. This is because the soy protein isolate in Comparative Example 1 was not modified, resulting in a lack of phosphate groups in its molecules. This weakens the ionic cross-linking between the core and wall materials, making the microcapsule structure more prone to disintegration under the mechanical and chemical action of simulated intestinal fluid. Furthermore, it loses its pH-responsive release characteristics, failing to efficiently ionize in the intestinal environment and promote targeted disintegration of the microcapsules. Consequently, more probiotics are lost before reaching their colonization sites due to premature or delayed destruction of the encapsulation structure, resulting in a lower survival rate of viable bacteria after small intestinal digestion. The protein-based microcapsules in Comparative Example 2 lacked a wall material, thus completely lacking the outer protective membrane composed of whey protein and sodium caseinate. Although the protein-based coating agent inside the core material provides some primary protection, it cannot effectively resist the dissolution and enzymatic degradation by bile salts in simulated intestinal fluid. Without this dense, continuous outer wall, probiotics are directly exposed to a harsh digestive environment, causing them to be partially inactivated as they pass through the front of the small intestine, resulting in a low number of live bacteria.

[0063] Table 2

[0064] According to Table 2, and considering Application Examples 1 and 2-3, the average final weight of piglets in Application Examples 2-3 was lower than that in Application Example 1. This is because the pig feed in Application Example 2 used protein-based microcapsules similar to those in Comparative Example 1. Compared to Application Example 1, the soy protein isolate in Application Example 2 was not modified, resulting in decreased gastrointestinal targeting and structural stability of the capsules. This led to a reduction in the number of viable bacteria that reached the posterior intestinal tract and successfully colonized. The synergistic effect of Clostridium butyricum and Lactobacillus plantarum was thus weakened, resulting in a weaker improvement in intestinal health compared to Application Example 1, ultimately leading to a smaller increase in piglet growth performance. The pig feed in Application Example 3 also used protein-based microcapsules similar to those in Comparative Example 2. Unlike Application Example 1, no wall material was added, resulting in significant loss of probiotics during feed processing, pelleting, and gastric digestion. The number of viable bacteria reaching the intestines and exerting their effects was severely insufficient. This made it difficult to fully realize the theoretical functions of probiotics, limiting their regulatory capacity on piglet intestinal flora and immune enhancement effects. Therefore, their growth-promoting effect was significantly lower than that of Application Example 1.

[0065] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A protein-based microcapsule, comprising a core material and a wall material, characterized in that, The core material includes a compound microbial agent, plant extracts and a protein-based coating agent, and the wall material includes whey protein and sodium caseinate. The compound microbial agent includes Clostridium butyricum and Lactobacillus plantarum; The plant extracts include Astragalus polysaccharide and Eucommia ulmoides leaf extract; The protein-based coating agent includes whey protein, zein, and modified soy protein isolate; The modified soy protein isolate is phosphorylated.

2. The protein-based microcapsule according to claim 1, characterized in that, The effective viable count ratio of Clostridium butyricum to Lactobacillus plantarum in the compound microbial agent is (1-2):(1-2), and the total effective viable count of the compound microbial agent is not less than 1.0 × 10⁻⁶. 10 CFU / g.

3. The protein-based microcapsule according to claim 1, characterized in that, The mass ratio of Astragalus polysaccharide to Eucommia ulmoides leaf extract in the plant extract is 1:(3-4); the mass ratio of whey protein to sodium caseinate in the wall material is 1:(1-2).

4. The protein-based microcapsule according to claim 1, characterized in that, The mass ratio of whey protein, zein, and modified soy protein isolate in the protein-based coating agent is 1:(1-2):(2-3).

5. The protein-based microcapsule according to claim 1, characterized in that, The modified soy protein isolate was obtained by the following preparation method: Soy protein isolate is dispersed in deionized water, phosphorylation reagent is added, pH is adjusted to 7-9, and the reaction is carried out at 30-50℃ for 2-4 hours. After that, the pH is adjusted to 3-6, and the product is obtained by centrifugation and drying.

6. The protein-based microcapsule according to claim 5, characterized in that, The mass ratio of soy protein isolate to phosphorylation reagent is 1:(0.01-0.1); the phosphorylation reagent includes one or more of sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, and sodium trimetaphosphate.

7. A method for preparing protein-based microcapsules, used to prepare protein-based microcapsules as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. A compound bacterial agent is prepared by mixing Clostridium butyricum and Lactobacillus plantarum. A protein-based coating agent is prepared by mixing whey protein, zein and modified soy protein isolate. S2. Add the compound microbial agent, protein-based coating agent and plant extract to the mixer, mix evenly and then make the core material. S3. Add the core material and wall material to the mixer, mix them evenly, and then spray dry to obtain the final product.

8. The method for preparing a protein-based microcapsule according to claim 7, characterized in that, The mass ratio of the compound microbial agent, protein-based coating agent, and plant extract is 1:(1.5-3):(0.3-2); the mass ratio of the core material and wall material is 1:(1-3).

9. The method for preparing a protein-based microcapsule according to claim 7, characterized in that, In step S3, the mixing time is 0.5 to 1 hour; the parameters for spray drying are: inlet temperature of 120 to 135°C, outlet temperature of 45 to 55°C, and feed peristaltic pump speed of 100 to 300 r / min.

10. The use of the protein-based microcapsules according to any one of claims 1-5 in pig feed.

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