Puffed fermented phosphorus-reduced high-digestibility rice byproduct feed

Abstract

The present application belongs to the technical field of feed processing, and provides a puffed fermented phosphorus-reduced high-digestive-utilization rice by-product feed, which adopts a multi-layer structure design of CO2 guided puffed foaming extrusion to form a porous base material, sodium alginate and chitosan are alternately deposited to construct an interface modification layer, and compound enzymes and probiotics are solidly fermented, three-dimensional pore structure with a median pore size of 20-60 mu m and a connected pore ratio of greater than or equal to 60%, phytase activity of 5000-10000 FTU / kg, total viable bacterial count of greater than or equal to 1x10 8 CFU / g, and an acid value increment of less than or equal to 2 mgKOH / g after 90 days of storage, solves the technical problems of low utilization of rice by-product phytic acid phosphorus, low survival rate and easy inactivation of compound enzymes and probiotics, and poor storage stability of high-oil rice bran, and has wide application value in the feed industry.

Description

Technical Field

[0001] This invention belongs to the field of feed processing technology and provides a puffed, fermented, phosphorus-reduced, and highly digestible rice by-product feed. Background Technology

[0002] With the rapid development of animal husbandry and the continuous upgrading of the feed industry, rice by-products, as an important plant protein feed resource, have received widespread attention and have enormous application potential in aquaculture, livestock and poultry farming, and other fields. In modern intensive farming systems, feed not only needs to provide sufficient nutrients but also requires high digestibility, good storage stability, and excellent bioactivity to meet the urgent needs of rapid animal growth, improved feed conversion efficiency, and reduced farming costs. Among these, the efficient utilization of phosphorus plays a crucial role in promoting animal bone development and maintaining normal physiological metabolism, while the effective loading and long-term activity maintenance of complex enzymes and probiotics directly affect feed digestibility and animal gut health. Simultaneously, the stability of feed products during production, transportation, and storage, especially antioxidant properties and shelf life, not only relates to product quality but also directly impacts the economic benefits and food safety of farming enterprises. Therefore, developing rice by-product feed technologies with high phosphorus utilization, excellent enzyme and bacterial activity retention, and good storage stability is of great significance for promoting technological progress in the feed industry and improving the overall efficiency of animal husbandry.

[0003] However, the development of rice by-product feed still faces many technical challenges and performance bottlenecks, severely restricting its widespread application in the feed industry. For example, Chinese patent CN110679728A discloses a method for preparing fermented rice bran feed and its application, but it suffers from the drawback of excessively high phytic acid-to-phosphorus ratio, leading to low phosphorus bioavailability. This is mainly due to the formation of insoluble complexes by phytic acid and phosphorus in rice by-products, and the lack of sufficient phytase in animals to decompose these complexes, forcing manufacturers to add large amounts of expensive inorganic phosphorus sources to meet animal nutritional needs. Similarly, Chinese patent CN116982673B discloses a feed additive containing complex enzymes and its preparation method, but it suffers from low loading efficiency of the complex enzymes and probiotics, and easy inactivation during extrusion processing and long-term storage. This is mainly because traditional loading technology lacks effective protection mechanisms; enzyme proteins and probiotic cells denature and become inactive under high-temperature extrusion conditions, and are also adversely affected by environmental factors such as moisture and oxygen during storage. For example, Chinese patent CN109170508A discloses a method for stabilizing rice bran, but it has the disadvantage of high oil content in rice bran leading to easy oxidation and poor storage stability. This is mainly because rice bran contains a large amount of unsaturated fatty acids, which are prone to lipid peroxidation during storage, resulting in a rapid increase in acid value, product rancidity and deterioration, and seriously shortening the shelf life of the product. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] The purpose of this invention is to provide a high-digestibility, high-efficiency extruded fermented rice by-product feed with reduced phosphorus content, which solves three major pain points of current rice by-products: high phytic acid phosphorus ratio leading to low phosphorus utilization and reliance on added inorganic phosphorus; low loading and survival rate of compound enzymes and probiotics, which are easily inactivated during extrusion / storage, resulting in poor function; and high oil content in rice bran leading to easy oxidation and poor storage stability (easy increase in acid value and short shelf life).

[0006] (2) Technical solution

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A type of extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed, characterized by its multi-layered structure from the inside out, comprising:

[0009] a) Porous expanded substrate: composed of rice bran, polished rice powder, and rice bran meal in a mass ratio of 0.9-1.1:0.9-1.1:0.9-1.1; formed into three-dimensional interconnected channels through CO2-guided expansion, foaming, and extrusion; the median pore size D50 is 20-60 μm, the proportion of interconnected pores is ≥60%, and the specific surface area is ≥1.0 m². 2 / g;

[0010] b) Interface modification layer: covering the outer surface and pore walls of the substrate, formed by alternating deposition of sodium alginate and chitosan and cross-linking and curing with calcium ions to form a 2-6 cycle double-layer continuous multilayer polyelectrolyte network;

[0011] c) Fermentation functional loading layer: A multi-layer polyelectrolyte network immobilizes a complex enzyme and probiotics. The amount of complex enzyme added is 100-1000 U / g (dry basis of the product), and the total inoculum amount of probiotics is 0.5%-5.0%. An active system is formed through two-stage solid-state fermentation, with phytase activity of 5000-10000 FTU / kg and a total viable count greater than or equal to 1×10⁻⁶. 8 CFU / g, wherein the probiotics are selected from one or more of the genera Bacillus and Lactobacillus.

[0012] Furthermore, the mass ratio of rice bran: rice polishing powder: rice bran meal is 0.9-1.1:0.9-1.1:0.9-1.1.

[0013] Furthermore, the median pore size D50 of the porous expanded substrate is 25-50 μm.

[0014] Furthermore, the thickness of the modified layer is 3-6 μm, and the degree of crosslinking is 0.6-0.9 mmol / g, based on the dry basis of the porous expanded substrate.

[0015] Furthermore, the complex enzyme contains one or more of xylanase, β-glucanase, and mannanase.

[0016] Furthermore, when the rice by-product feed is stored at 25°C and 70% relative humidity for 90 days, the increase in acid value is less than or equal to 2 mg KOH / g, calculated based on the initial measurement value obtained no more than 4 hours after preparation.

[0017] As a concept of this invention, the multi-layer structure design is primarily used to enhance the digestibility and utilization of rice by-product feed. This design achieves the organic integration and synergistic effect of multiple technological strategies by constructing a multi-layered functional structure from the inside out. Specifically, the porous extruded substrate uses a composite ratio of rice bran, polished rice powder, and rice bran meal. A three-dimensional interconnected pore structure is formed through a CO2-guided extrusion foaming process, providing an ideal carrier platform for the subsequent construction of functional layers. This also significantly increases the specific surface area and improves the contact efficiency with digestive enzymes. The interface modification layer, constructed using alternating deposition techniques of sodium alginate and chitosan, forms a stable multi-layered polyelectrolyte network structure. This network, under the cross-linking and solidification effect of calcium ions, forms a continuous protective barrier, effectively blocking the adverse effects of the external environment on the internal active ingredients. The fermentation functional loading layer immobilizes complex enzymes and probiotics within a multi-layered polyelectrolyte network. A two-stage solid-state fermentation process constructs the active system. The synergistic effect of xylanase, β-glucanase, and mannanase significantly improves the degradation efficiency of cellulose substances. Furthermore, the co-fermentation of Bacillus and Lactobacillus not only produces highly active phytase but also establishes a stable microecological balance. This multi-layered structural design allows for a synergistic effect of physical modification of the expanded substrate, chemical protection of the polyelectrolyte network, and biotransformation through microbial fermentation. This results in a significant improvement in phosphorus utilization, effective assurance of active ingredient stability, and comprehensive improvement in product storage performance.

[0018] This invention also discloses a method for preparing extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed, comprising the following steps:

[0019] S1 involves pre-impregnating a mixture of rice bran, polished rice powder, and rice bran meal in a natural deep eutectic solvent and recovering the solvent. The natural deep eutectic solvent is composed of choline chloride, a hydrogen bond donor, and water. The hydrogen bond donor is selected from one or more of glycerol and lactic acid.

[0020] S2 involves CO2-guided puffing and foaming extrusion of materials with a moisture content of 12%-16%. The first temperature zone is 90℃, the second temperature zone is 110℃, and the third temperature zone is 120-125℃. The CO2 injection pressure is 0.7-1.0MPa, and the injection mass ratio is 0.5%-1.0% (all on a dry basis). The residence time is 30-60s, resulting in a porous puffed substrate. The CO2 injection zone is located at the end of the second temperature zone or the beginning of the third temperature zone, and the screw speed is 250-380rpm.

[0021] S3 undergoes layer-by-layer self-assembly after the discharged material is cooled to 35-40℃. Sodium alginate solution and chitosan solution are applied sequentially. The sodium alginate solution has a mass fraction of 0.2%-1.0% and a pH value of 6.0-7.5, while the chitosan solution has a mass fraction of 0.1%-0.5% and a pH value of 4.5-5.5. The calcium chloride concentration is 10-100 mmol / L, and the single-step contact time is 30-180 s for each step. The resulting modified layer has a film thickness of 2-10 μm and a crosslinking degree of 0.5-1.0 mmol / g.

[0022] S4 is loaded with compound enzymes and probiotics and undergoes two-stage solid-state fermentation. The first stage is carried out at a temperature of 40-42℃ for 18-24 hours, and the second stage is carried out at a temperature of 35-37℃ for 24-36 hours. The fermentation moisture content is 38%-42%, and the final pH value is 4.2-4.8. The finished product is obtained after drying and sieving.

[0023] Furthermore, the natural deep eutectic solvent in step S1 is choline chloride:glycerol:water = 1:2:2, with a molar ratio of 2wt.%-5wt.% based on the dry basis of the raw materials. The pre-soaking temperature is 30-40 ℃, the time is 10-20 min, and the recovery rate is ≥90%.

[0024] Furthermore, in step S2, the CO2 injection zone is located in the latter part of the second temperature zone or the former part of the third temperature zone, with a screw speed of 250-380 rpm.

[0025] Furthermore, the residual natural eutectic solvent in the finished product is ≤0.2% (w / w).

[0026] This invention employs a step-by-step synergistic process primarily for enhancing the overall functional performance of rice by-product feed. The preparation method, through a meticulously designed four-step process, achieves the organic unity of raw material pretreatment, structural construction, interface modification, and functional loading. First, a natural deep eutectic solvent pre-impregnation process utilizes a green solvent system composed of choline chloride, glycerol, and water to deeply swell a mixture of rice bran, polished rice powder, and rice bran meal. This pretreatment not only effectively disrupts the dense structure of the raw materials, reducing subsequent processing resistance, but also lays the foundation for the smooth progress of the extrusion process. The CO2-guided extrusion foaming and extrusion process employs a temperature-zone control strategy, combined with precise CO2 injection parameters, to form an ideal three-dimensional porous structure under specific material moisture conditions, providing ample space for the subsequent loading of functional components. The layer-by-layer self-assembly process, through the alternating application of sodium alginate and chitosan solutions, constructs a stable multilayer polyelectrolyte network under the action of a calcium chloride crosslinking system. This network structure forms a continuous protective film layer under suitable pH conditions, effectively improving the stability of the internal structure. The two-stage solid-state fermentation process employs a temperature-decreasing control mode, combined with precise moisture and pH regulation, to achieve efficient loading and activation of compound enzymes and probiotics. This allows the triple effects of physical modification, chemical cross-linking, and biotransformation to mutually promote each other, jointly improving the product's phosphorus utilization efficiency, activity retention capacity, and storage stability, thus realizing a performance multiplication effect brought about by process synergy.

[0027] (3) Beneficial technical effects

[0028] 1. Significantly improves phosphorus utilization efficiency: Through multi-layer structure design, the complex enzyme and probiotics are efficiently immobilized. The two-stage solid-state fermentation process produces highly active phytase, which effectively decomposes phytate phosphorus complexes in rice by-products, releases bound phosphorus, and reduces dependence on external inorganic phosphorus. This fundamentally solves the key problem of low phosphorus utilization caused by high phytate phosphorus ratio, and achieves a significant improvement in the phosphorus nutritional value of feed.

[0029] 2. Effectively ensures the stability of active ingredients: The multi-layered polyelectrolyte network constructed by alternating deposition of sodium alginate and chitosan forms a continuous protective barrier under the cross-linking and solidification effect of calcium ions. This effectively blocks the adverse effects of high-temperature extrusion and storage environment on the complex enzymes and probiotics, significantly improving the load survival rate and long-term activity retention of xylanase, β-glucanase, mannanase, as well as Bacillus and Lactobacillus, ensuring that the functional components continue to play a role throughout the entire product life cycle.

[0030] 3. Significantly improves product storage stability: The three-dimensional interconnected pore structure formed by CO2-guided puffing and foaming extrusion, combined with the encapsulation and protection of a multi-layer polyelectrolyte network, effectively reduces the oxidation rate of unsaturated fatty acids in rice bran, inhibits lipid peroxidation, significantly controls the increase in acid value during storage, extends the product shelf life, and solves the technical problem of poor storage stability caused by the high oil content and easy oxidation of rice bran.

[0031] 4. Comprehensive improvement of feed digestibility and utilization: The porous extruded substrate significantly increases the specific surface area, improves the contact efficiency with digestive enzymes, and, combined with the synergistic degradation effect of the compound enzyme system, effectively breaks down cellulose anti-nutritional factors, improves the digestibility and absorption performance of feed nutrients, and at the same time, the stable microecological balance established by probiotic fermentation further promotes intestinal health, thereby achieving a comprehensive improvement in the overall digestibility and utilization of feed. Attached Figure Description

[0032] Figure 1 This invention relates to the effect of CO2 injection pressure on phytase activity and phosphorus digestibility.

[0033] Figure 2 This invention relates to the effect of the number of interface modification layer cycles on enzyme activity stability and viable bacterial survival rate.

[0034] Figure 3 This invention relates to the effect of calcium ion crosslinking concentration on the degree of crosslinking and enzyme activity stability.

[0035] Figure 4 The image shows the infrared Fourier transform spectrum of a mixture of rice bran, polished rice powder, and rice bran meal in Example 1 of this invention.

[0036] Figure 5 The infrared Fourier transform spectrum of the mixture of choline chloride, glycerol, and water in a ratio of 1:2:2 (1:2) after pre-impregnation in a natural deep eutectic solvent is shown in Example 1 of this invention.

[0037] Figure 6 This is the infrared Fourier spectrum of the porous expanded substrate after CO2-guided expansion foaming and extrusion in Example 1 of the present invention.

[0038] Figure 7 The infrared Fourier spectrum of a bilayer sample of Example 1 of the present invention, which is formed by alternating deposition of sodium alginate and chitosan and cross-linking with calcium ions for one cycle.

[0039] Figure 8 The infrared Fourier spectra of two bilayer samples of Example 1 of the present invention, which are alternately deposited with sodium alginate and chitosan and then cross-linked and cured with calcium ions.

[0040] Figure 9 The infrared Fourier transform spectra of three bilayer samples of sodium alginate and chitosan alternately deposited and cross-linked with calcium ions in Example 1 of this invention are shown.

[0041] Figure 10 The infrared Fourier spectra of four cycles of bilayer samples of sodium alginate and chitosan alternately deposited and cross-linked with calcium ions in Example 1 of this invention are shown.

[0042] Figure 11 The images show the infrared Fourier transform spectra of the four-cycle bilayer samples from Example 1 of this invention that were not subjected to calcium ion crosslinking and curing.

[0043] Figure 12 The image shows the infrared Fourier transform spectrum of the sample after two-stage solid-state fermentation of a complex enzyme and probiotics immobilized in a multilayer polyelectrolyte network, as described in Example 1 of this invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0045] Example 1

[0046] This embodiment provides an extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed. It has a multi-layered structure from the inside out, comprising: a porous extruded substrate composed of rice bran, polished rice powder, and rice bran meal in a mass ratio of 1.0:1.0:1.0; formed by CO2-guided extrusion and foaming to create three-dimensional interconnected channels; a median pore size (D50) of 35 μm; an interconnected pore ratio of 65%; and a specific surface area of ​​1.2 m². 2 / g; The interface modification layer covers the outer surface and pore walls of the substrate in this embodiment. It is formed by alternating deposition of sodium alginate and chitosan and cross-linking with calcium ions to form a four-cycle, double-layer, continuous, multi-layer polyelectrolyte network. The film thickness of the modification layer in this embodiment is 4 μm, and the degree of cross-linking is 0.75 mmol / g; The fermentation functional loading layer immobilizes a complex enzyme and probiotics in the multi-layer polyelectrolyte network. The amount of complex enzyme added is 500 U / g on a dry basis of the product, and the total inoculum amount of probiotics is 2.5%. An active system is formed through two-stage solid-state fermentation. The phytase activity is 7500 FTU / kg, and the total viable count is 5 × 10⁻⁶. 8CFU / g, in this embodiment, the probiotics are selected from a mixture of Bacillus subtilis and Lactobacillus plantarum in a mass ratio of 1:1, and the complex enzyme is selected from a mixture of xylanase and β-glucanase in a mass ratio of 1:1. The preparation method includes: S1 pre-impregnating a mixture of rice bran, polished rice powder and rice bran meal in a natural deep eutectic solvent and recovering the solvent. In this embodiment, the natural deep eutectic solvent is choline chloride:glycerol:water = 1:2:2, with a dosage of 3.5 wt.% based on the dry basis of the raw materials. The pre-impregnation temperature is 35℃, and the time is 15 min; S2 CO2-guided puffing, foaming and extrusion are carried out under the condition that the material moisture content is 14%. The temperature of the first temperature zone is 90℃, the temperature of the second temperature zone is 110℃, the temperature of the third temperature zone is 122℃, the CO2 injection pressure is 0.8 MPa, and the injection mass ratio is 0.75. The residence time was 45s, and the screw speed was 315rpm; S3 underwent layer-by-layer self-assembly after being cooled to 37℃ after discharge. The sodium alginate solution had a mass fraction of 0.6% and a pH of 6.5, the chitosan solution had a mass fraction of 0.3% and a pH of 5.0, the calcium chloride concentration was 55mmol / L, and the single-step contact time was 105s; S4 was loaded with compound enzymes and probiotics and underwent two-stage solid-state fermentation. The first stage was at 41℃ for 21h, and the second stage was at 36℃ for 30h. The fermentation moisture content was 40%, and the final pH value was 4.5.

[0047] Features of this embodiment: It adopts a balanced formula ratio and moderate process parameters, which has good process stability and product consistency. It is suitable for large-scale industrial production, and is especially suitable for aquaculture feed production with high requirements for product quality stability.

[0048] Example 2

[0049] This embodiment provides an extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed. It has a multi-layered structure from the inside out, comprising: a porous extruded substrate composed of rice bran, polished rice powder, and rice bran meal in a mass ratio of 0.9:0.9:1.1; formed by CO2-guided extrusion and foaming to create three-dimensional interconnected channels; a median pore size (D50) of 45 μm; an interconnected pore ratio of 75%; and a specific surface area of ​​1.5 m². 2 / g; The interface modification layer covers the outer surface and pore walls of the substrate in this embodiment. It is formed by alternating deposition of sodium alginate and chitosan and cross-linking with calcium ions to form a 6-cycle double-layer continuous multilayer polyelectrolyte network. The film thickness of the modification layer in this embodiment is 5μm and the degree of cross-linking is 0.8mmol / g; The fermentation functional loading layer immobilizes a complex enzyme and probiotics in the multilayer polyelectrolyte network. The amount of complex enzyme added is 800U / g on a dry basis of the product, and the total inoculum amount of probiotics is 4.0%. An active system is formed through two-stage solid-state fermentation. The phytase activity is 9000FTU / kg, and the total viable count is 8×10 8CFU / g, in this embodiment, the probiotics are selected from Bacillus licheniformis, and the complex enzyme is selected from xylanase. The preparation method includes: S1, pre-impregnating a mixture of rice bran, polished rice powder, and rice bran meal in a natural deep eutectic solvent and recovering the solvent. In this embodiment, the natural deep eutectic solvent is choline chloride:glycerol:water = 1:2:2, with a dosage of 4.5 wt.% based on the dry basis of the raw materials. The pre-impregnation temperature is 38℃, and the time is 18 min; S2, CO2-guided puffing, foaming, and extrusion is performed under conditions where the material moisture content is 15%. The first temperature zone is 90℃, the second temperature zone is 110℃, and the third temperature zone is 124℃. The CO2 injection pressure is 0.9 MPa, and the injection mass ratio is 0.9. The residence time was 55s, and the screw speed was 350rpm; S3 underwent layer-by-layer self-assembly after being cooled to 38℃ after discharge. The sodium alginate solution had a mass fraction of 0.8% and a pH of 7.0, the chitosan solution had a mass fraction of 0.4% and a pH of 4.8, the calcium chloride concentration was 80mmol / L, and the single-step contact time was 150s; S4 was loaded with compound enzymes and probiotics and underwent two-stage solid-state fermentation. The first stage was at 42℃ for 22h, and the second stage was at 37℃ for 32h. The fermentation moisture content was 41%, and the final pH value was 4.3.

[0050] Features of this embodiment: Enhanced enzyme activity and probiotic loading, with a higher porosity and specific surface area design to maximize bioactivity and digestibility, making it particularly suitable for the production and application of high-grade livestock and poultry feed and functional feed additives.

[0051] Example 3

[0052] This embodiment provides an extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed. It has a multi-layered structure from the inside out, comprising: a porous extruded substrate composed of rice bran, polished rice powder, and rice bran meal in a mass ratio of 1.1:1.1:0.9; formed by CO2-guided extrusion and foaming to create three-dimensional interconnected channels; a median pore size (D50) of 30 μm; an interconnected pore ratio of 68%; and a specific surface area of ​​1.1 m². 2 / g; The interface modification layer covers the outer surface and pore walls of the substrate in this embodiment. It is formed by alternating deposition of sodium alginate and chitosan and cross-linking with calcium ions to form a three-cycle, double-layer, continuous, multi-layer polyelectrolyte network. The film thickness of the modification layer in this embodiment is 6 μm, and the degree of cross-linking is 0.9 mmol / g; The fermentation functional loading layer immobilizes a complex enzyme and probiotics in the multi-layer polyelectrolyte network. The amount of complex enzyme added is 300 U / g on a dry basis of the product, and the total inoculum amount of probiotics is 1.5%. An active system is formed through two-stage solid-state fermentation. The phytase activity is 6000 FTU / kg, and the total viable count is 2 × 10⁻⁶. 8CFU / g, the probiotics in this embodiment are selected from Bacillus pasteurellii, and the complex enzyme includes β-glucanase. The preparation method includes: S1 pre-impregnation of a mixture of rice bran, polished rice powder, and rice bran meal in a natural deep eutectic solvent and solvent recovery. In this embodiment, the natural deep eutectic solvent is choline chloride:glycerol:water = 1:2:2, with a dosage of 2.5 wt.% on a dry basis of the raw materials. The pre-impregnation temperature is 32℃, and the time is 12 min. S2 CO2-guided puffing, foaming, and extrusion are performed under conditions where the material moisture content is 13%. The first temperature zone is 90℃, the second temperature zone is 110℃, and the third temperature zone is 121℃. The CO2 injection pressure is 0.7 MPa, and the injection mass ratio is 0.6. The residence time was 35s, and the screw speed was 280rpm. After the discharge was cooled to 36℃, S3 underwent layer-by-layer self-assembly. The sodium alginate solution had a mass fraction of 0.4% and a pH of 6.2, the chitosan solution had a mass fraction of 0.2% and a pH of 5.2, the calcium chloride concentration was 30mmol / L, and the single-step contact time was 60s. S4 was loaded with compound enzymes and probiotics and underwent two-stage solid-state fermentation. The first stage was at 40℃ for 20h, and the second stage was at 35℃ for 28h. The fermentation moisture content was 39%, and the final pH value was 4.6.

[0053] Features of this embodiment: It emphasizes product storage stability, adopts a thicker protective film layer and a high degree of cross-linking design, and has excellent antioxidant properties and long shelf life, making it particularly suitable for feed products that require long-term storage and long-distance transportation.

[0054] Example 4

[0055] This embodiment provides an extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed. It has a multi-layered structure from the inside out, comprising: a porous extruded substrate composed of rice bran, polished rice powder, and rice bran meal in a mass ratio of 0.9:1.1:1.1. Through CO2-guided extrusion and foaming, three-dimensional interconnected channels are formed, with a median pore size (D50) of 50 μm, an interconnected pore ratio of 70%, and a specific surface area of ​​1.8 m². 2 / g; The interface modification layer covers the outer surface and pore walls of the substrate in this embodiment. It is formed by alternating deposition of sodium alginate and chitosan and cross-linking with calcium ions to form a two-cycle, double-layer, continuous multilayer polyelectrolyte network. The film thickness of the modification layer in this embodiment is 3 μm, and the degree of cross-linking is 0.6 mmol / g; The fermentation functional loading layer immobilizes a complex enzyme and probiotics in the multilayer polyelectrolyte network. The amount of complex enzyme added is 150 U / g on a dry basis of the product, and the total inoculum amount of probiotics is 1.0%. An active system is formed through two-stage solid-state fermentation. The phytase activity is 5500 FTU / kg, and the total viable count is 1×10⁻⁶. 8CFU / g, in this embodiment, the probiotics are selected from Lactobacillus rhamnosus, and the complex enzyme is selected from a mixture of xylanase and mannanase in a mass ratio of 2:1. The preparation method includes: S1 Pre-impregnating a mixture of rice bran, polished rice powder, and rice bran meal in a natural deep eutectic solvent and recovering the solvent. In this embodiment, the natural deep eutectic solvent is choline chloride:glycerol:water = 1:2:2, with a dosage of 5.0 wt.% based on the dry basis of the raw materials. The pre-impregnation temperature is 40℃, and the time is 20 min; S2 CO2-guided puffing, foaming, and extrusion are carried out under the condition that the material moisture content is 12%. The temperature of the first temperature zone is 90℃, the temperature of the second temperature zone is 110℃, the temperature of the third temperature zone is 125℃, the CO2 injection pressure is 1.0 MPa, and the injection mass ratio is 1.0%. The residence time was 60s, and the screw speed was 380rpm. S3 underwent layer-by-layer self-assembly after being cooled to 40℃ after discharge. The sodium alginate solution had a mass fraction of 1.0% and a pH of 7.5, the chitosan solution had a mass fraction of 0.5% and a pH of 4.5, the calcium chloride concentration was 100mmol / L, and the single-step contact time was 180s. S4 was loaded with compound enzymes and probiotics and underwent two-stage solid-state fermentation. The first stage was at 40℃ for 24h, and the second stage was at 35℃ for 36h. The fermentation moisture content was 42%, and the final pH value was 4.8.

[0056] Features of this embodiment: It adopts boundary process parameters, has the largest pore size and specific surface area, and the simplified double-layer structure design reduces production costs, making it particularly suitable for the production needs of cost-sensitive feed markets and primary processing enterprises.

[0057] Comparative Example 1: It is basically the same as Example 1, except that the CO2 injection pressure in step S2 is set to 0.3 MPa, while other preparation conditions, including injection mass ratio, residence time, screw speed, etc., remain unchanged.

[0058] Comparative Example 2: It is basically the same as Example 1, except that in step S2, the temperature of the third temperature zone is set to 100°C, while the temperatures of the first and second temperature zones remain unchanged at 90°C and 110°C, respectively.

[0059] Comparative Example 3: It is basically the same as Example 1, except that the moisture content of the material is controlled at 8% in step S2, while other puffing process parameters, including temperature distribution and CO2 injection conditions, remain unchanged.

[0060] Comparative Example 4: It is basically the same as Example 1, except that the screw speed is set to 150 rpm in step S2, while other puffing and foaming extrusion parameters remain unchanged.

[0061] Comparative Example 5: It is basically the same as Example 1, except that the dwell time in step S2 is adjusted to 15s, while other extrusion process conditions, including temperature, pressure, screw speed, etc., remain unchanged.

[0062] Comparative Example 6: It is basically the same as Example 1, except that in step S3, the interface modification layer forms a one-cycle bilayer continuous multilayer polyelectrolyte network, while the concentrations of sodium alginate and chitosan solution and other layer-by-layer self-assembly conditions remain unchanged.

[0063] Comparative Example 7: Basically the same as Example 1, except that the calcium chloride concentration in step S3 was set to 200 mmol / L, while the concentrations of sodium alginate and chitosan solution and the contact time, and other conditions remained unchanged.

[0064] Comparative Example 8: Basically the same as Example 1, except that in step S3 the mass fraction of sodium alginate solution was adjusted to 0.1%, the pH value was kept at 6.5, and other self-assembly process conditions remained unchanged.

[0065] Comparative Example 9: Basically the same as Example 1, except that in step S3 the mass fraction of chitosan solution was adjusted to 0.8%, the pH value was kept at 5.0, and other layer-by-layer deposition conditions remained unchanged.

[0066] Comparative Example 10: It is basically the same as Example 1, except that the total amount of probiotics inoculated in step S4 is adjusted to 0.2%, while the amount of compound enzyme added and the two-stage solid-state fermentation conditions remain unchanged.

[0067] Comparative Example 11: It is basically the same as Example 1, except that the amount of compound enzyme added in step S4 is adjusted to 50 U / g, while the amount of probiotic inoculation and fermentation process conditions remain unchanged.

[0068] Comparative Example 12: It is basically the same as Example 1, except that in step S4, the temperature of the first stage solid-state fermentation is adjusted to 50°C, the fermentation time is still kept at 21h, and the fermentation conditions and other process parameters of the second stage remain unchanged.

[0069] Comparative Example 13: It is basically the same as Example 1, except that the amount of natural deep eutectic solvent in step S1 is adjusted to 8 wt.% based on the dry basis of the raw material, and the pre-soaking temperature and time are kept unchanged at 35°C and 15 min, respectively.

[0070] Performance testing:

[0071] Phytic acid phosphorus content determination experiment: The test subject was the finished feed product of extruded fermented rice by-products with reduced phosphorus content and high digestibility. The purpose of the test was to quantitatively evaluate the residual phytic acid phosphorus content in the feed and verify the effect of phytic acid enzymatic hydrolysis of phosphorus. The test principle is based on the colorimetric reaction principle of phytic acid forming a colored complex with ferric chloride under acidic conditions. The experimental method adopted the Wade reagent colorimetric method. 2.00g of feed sample pulverized through a 40-mesh sieve was extracted with 2.4% hydrochloric acid solution. After centrifugation, the supernatant was collected, and Wade reagent was added for color development. The absorbance value was measured at a wavelength of 500nm, and the phytic acid phosphorus content was calculated through a standard curve. Key parameters included extraction temperature of room temperature (25±2℃), extraction time of 4 hours, centrifugation speed of 3000rpm for 10 minutes, and color development time of 15 minutes. Data processing used the average value of three parallel determinations. The phytic acid phosphorus content was calculated on a dry matter basis, requiring a relative standard deviation of ≤5% and a target control value of ≤0.15%.

[0072] In vitro phosphorus digestibility determination experiment: The test subject was extruded fermented rice by-product feed with reduced phosphorus and high digestibility. The purpose of the test was to evaluate the bioavailability of phosphorus in the feed under the animal digestive tract environment. The test principle is based on simulating the animal gastrointestinal digestive environment, releasing available phosphorus through enzymatic hydrolysis, and measuring the change in phosphorus content before and after digestion. The experimental method adopted a three-step in vitro digestion method, sequentially simulating gastric digestion (pepsin, pH 2.0, 37℃, 2 hours), small intestinal digestion (pancreatic enzymes and bile salts, pH 6.8, 37℃, 2 hours), and large intestinal digestion (cellulase, pH 6.8, 37℃, 4 hours). After each digestion step, the supernatant was collected by centrifugation, and the soluble phosphorus content was determined by the molybdenum blue colorimetric method. The standard was based on AOAC Official Method 2000.12 "In vitro determination method for phosphorus bioavailability in feed". Key parameters included a constant temperature oscillation frequency of 120 rpm, enzyme concentration strictly prepared according to the standard, and pH control accuracy ±0.1. Phosphorus digestibility is calculated as (soluble phosphorus after digestion - blank control) / total phosphorus × 100%, with a requirement that the difference between parallel samples be ≤3% and the target phosphorus digestibility be ≥85%.

[0073] Phytase Activity Assay: The test subject was phytase in extruded fermented rice by-product feed with reduced phosphorus and high digestibility. The purpose of the test was to quantitatively evaluate the enzyme activity level of phytase in the feed and verify the enzyme activity protection effect. The test principle is based on the release of inorganic phosphate by phytase hydrolyzing sodium phytate substrate, and the enzyme activity is calculated by measuring the amount of phosphorus released using the molybdenum blue colorimetric method. Experimental method: The feed sample was extracted with an acetate buffer solution at pH 5.5, reacted with 5.1 mmol / L sodium phytate substrate at 37℃ for 30 minutes, and the reaction was terminated by adding trichloroacetic acid. After centrifugation, the supernatant was collected and the absorbance was measured at a wavelength of 660 nm using molybdenum blue reagent. The standard was GB / T 18634-2009 "Determination of Phytase Activity in Feed - Spectrophotometric Method". Key parameters included the pH of the extraction solution (5.5±0.1), reaction temperature (37±0.5℃), substrate concentration (5.1±0.1 mmol / L), and reaction time (strictly controlled at 30±1 minutes). Data processing was performed with 1 μmol of phosphate released per minute as 1 enzyme activity unit (FTU). The results were calculated using a standard curve and expressed as FTU / kg. The reproducibility coefficient of variation was required to be ≤8%, and the target enzyme activity was ≥5000 FTU / kg.

[0074] Total Viable Bacteria Count Determination Experiment: The test subject is the probiotic community in extruded fermented rice by-product feed with reduced phosphorus and high digestibility. The purpose of the test is to quantitatively assess the quantity level of active probiotics in the feed and verify the survival rate and loading effect of the strains. The test principle is based on the counting principle of visible colonies formed by viable bacteria on suitable culture media. The experimental method adopts the plate count method. Feed samples are prepared into a series of dilutions with sterile physiological saline and inoculated onto MRS agar medium (lactate bacteria) and nutrient agar medium (Bacillus), respectively. They are incubated at 37℃ under anaerobic (lactate bacteria) or aerobic (Bacillus) conditions for 48-72 hours, and the number of colonies formed is counted. Key parameters include culture temperature 37±1℃, relative humidity ≥90%, CO2 concentration for anaerobic culture 5-10%, and colony diameter ≥0.5mm. Data processing is calculated by multiplying the colony count of the plate at the suitable dilution by the dilution factor. The results are expressed as CFU / g. The count difference between parallel samples is required to be ≤10%, and the target total viable bacteria count is ≥1×10⁻⁶. 8 CFU / g.

[0075] Enzyme Activity Stability Determination Experiment During Storage: The test subject was extruded fermented rice by-product feed with reduced phosphorus and high digestibility, stored for different periods under specified storage conditions. The purpose of the test was to evaluate the ability of phytase in the feed to retain activity during long-term storage. The test principle is based on periodically measuring the changes in phytase activity of stored samples and calculating the enzyme activity retention rate to evaluate stability. Experimental Method: Feed samples were packaged in sealed containers and stored at 25±2℃ and 65±5% relative humidity. Samples were taken on days 0, 30, 60, and 90, and phytase activity was measured according to GB / T 18634-2017. The retention rate of activity at each time point relative to the initial activity was calculated. Key parameters included storage temperature 25±2℃, relative humidity 65±5%, light protection, good airtight packaging, and sampling time point error ≤24 hours. Data processing is performed to calculate enzyme activity retention rate = (enzyme activity in storage t days / initial enzyme activity) × 100%, and an enzyme activity-time curve is plotted. The requirement is that the enzyme activity retention rate after 90 days is ≥80% and the coefficient of variation is ≤10%.

[0076] Acid Value Determination Experiment: The test subject was the oil component in extruded fermented rice by-product feed with reduced phosphorus and high digestibility. The purpose of the test was to assess the degree of oxidative rancidity of the oil in the feed and verify its antioxidant stability. The test principle is based on the neutralization reaction of free fatty acids with potassium hydroxide, and the acid value is calculated by titrating the amount of alkali consumed. Experimental Method: 5.00g of uniformly pulverized feed sample was extracted with oil using a mixed solvent of diethyl ether and isopropanol (3:2). After filtration, 50mL of the filtrate was taken, phenolphthalein indicator was added, and titration was performed with 0.1mol / L potassium hydroxide ethanol solution until a faint red color persisted for 30 seconds without fading. The standard was based on GB5009.229-2016 "National Food Safety Standard - Determination of Acid Value in Food". Key parameters included the extraction solvent ratio of diethyl ether:isopropanol = 3:2, extraction time of 4 hours, titration speed of 1-2 drops / second, endpoint color retention time of 30 seconds, and room temperature conditions of 20-25℃. The formula for calculating acid value in data processing is: acid value (mg KOH / g) = (V1-V0) × c × 56.1 / m, where V1 is the volume of alkali consumed by the sample, V0 is the volume consumed by the blank, c is the concentration of alkali, and m is the mass of the sample. The relative deviation of parallel determinations is required to be ≤5%, and the target control value is ≤3.0 mg KOH / g.

[0077] Comprehensive Shelf-Life Stability Evaluation Experiment: The test subject is the comprehensive quality changes of extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed under simulated actual storage conditions. The purpose of the test is to comprehensively evaluate the product's quality stability and functional retention ability within the expected shelf life. The test principle is based on the accelerated aging test principle, predicting shelf life by monitoring the time-varying patterns of multiple key quality indicators. Experimental Method: Feed samples were grouped according to commercial packaging and stored under conditions of 25℃ / 60%RH (room temperature group) and 40℃ / 75%RH (accelerated aging group), respectively. Key indicators such as phytase activity, viable cell count, acid value, moisture, and crude protein were periodically tested to establish a quality change kinetic model. The standard is based on GB / T 20189-2006 "General Rules for Feed Storage". Key parameters include room temperature storage of 25±2℃ and relative humidity of 60±5%, and accelerated storage of 40±2℃ and relative humidity of 75±5%. The testing frequency is once a month, and the storage period is 6 months. Data processing uses the Arrhenius equation to establish a quality decay kinetic model, calculates shelf life under normal temperature conditions, requires key functional indicators to maintain ≥80%, sensory quality to show no significant deterioration, and microbiological indicators to meet feed hygiene standards.

[0078] Figure 1 This invention investigates the effect of CO2 injection pressure on phytase activity and phosphorus digestibility. Fixed conditions included four cycles of the interface modification layer, a calcium chloride concentration of 55 mmol / L, a compound enzyme addition of 500 U / g, and a probiotic inoculum amount of 2.5%, with other process parameters identical to those in Example 1. The variable parameter was the CO2 injection pressure, ranging from 0.3 to 1.3 MPa. Results showed that phytase activity and phosphorus digestibility peaked around 0.85-0.87 MPa, reaching 7650 FTU / kg and 88.1%, respectively. This demonstrates that a moderate foaming pressure can form an optimal three-dimensional interconnected pore structure; too low a pressure leads to insufficient foaming, affecting the specific surface area, while too high a pressure causes pore wall collapse, reducing structural stability. Figure 2 This study investigated the effect of the number of interface modification layer cycles on enzyme activity stability and viable bacterial survival rate. Fixed conditions included a CO2 injection pressure of 0.8 MPa, a calcium chloride concentration of 55 mmol / L, and other parameters consistent with baseline conditions. The variable parameter was the number of self-assembly cycles of the polyelectrolyte layers, ranging from 1 to 9. Results showed that enzyme activity stability and viable bacterial survival rate reached their highest values ​​(89-90%) and 91-92%, respectively, at 4-5 cycles. This demonstrates that an appropriate membrane thickness provides optimal protection; too few layers fail to effectively block external environmental influences, while too many layers hinder the mass transfer and release of functional molecules. Figure 3This invention investigates the effect of calcium ion crosslinking concentration on the degree of crosslinking and enzyme activity stability. The fixed conditions were a CO2 injection pressure of 0.8 MPa, four cycles of the interface modification layer, and other process parameters remaining constant. The variable parameter was the calcium chloride concentration, ranging from 10 to 200 mmol / L. The results showed that the degree of crosslinking increased with increasing calcium ion concentration, but the enzyme activity stability reached a peak of 89% around 70 mmol / L, demonstrating an optimal balance between crosslinking degree and functional preservation. Excessive crosslinking, while improving structural stability, inhibited the conformational flexibility of the enzyme molecule and substrate contact efficiency.

[0079] Figure 4 The infrared Fourier transform spectrum of the mixture of rice bran, polished rice powder, and rice bran meal in Example 1 of this invention shows the polysaccharide backbone characteristics of the substrate (1150-1000 cm⁻¹). -1 For COC / CO fingerprint strips, 2920 / 2850 cm -1 For aliphatic CH stretching, 1740 cm -1 It is a weak ester carbonyl group, 1465 cm -1 (for CH2 bending), providing a chemical reference for subsequent process stages; Figure 5 The infrared Fourier transform spectrum of the mixture of choline chloride:glycerol:water = 1:2:2 pre-impregnated with a natural deep eutectic solvent, as shown in Example 1 of this invention, is compared with the substrate at 1110 and 1060 cm⁻¹. -1 Significant enhancement was observed, and the height was 3200–3400 cm. -1 Broadband widening indicates trace residues of the glycerol / choline hydrogen bond network while the polysaccharide fingerprint band is maintained, providing a baseline for subsequent puffing recovery and residue inhibition. Figure 6 This is the infrared Fourier transform spectrum of the porous expanded substrate after CO2-guided foaming and extrusion in Example 1 of the present invention, 1110 / 1060 cm⁻¹. -1 The natural deep eutectic solvent-related absorption is significantly reduced at 1150–1000 cm⁻¹. -1 Polysaccharide fingerprint strip with 1740, 2920 / 2850cm -1 The retention of the main band proves that the expansion process effectively reduces solvent residue without damaging the main chain, providing a stable chemical base for layer-by-layer self-assembly. Figure 7 The infrared Fourier transform spectrum of a bilayer sample from Example 1 of this invention, showing alternating deposition of sodium alginate and chitosan followed by calcium ion crosslinking and curing for one cycle, is shown, with the 1655 cm⁻¹ region added or enhanced relative to the substrate. -1 (Chitosanamide I) and approximately 1535cm -1 (NH3) + (bent) and approximately 1608–1612 / 1415 cm -1 Alginic acid COO - The paired absorption indicates that the first double layer has been successfully constructed; Figure 8The infrared Fourier transform spectra of two periodic bilayer samples from Example 1 of this invention show a continuous enhancement of the characteristic peaks of chitosan and alginate, with an increase in the ratios of I1535 / I1415 and I1655 / I1415, and a rise in COO. - The anti-symmetric scaling increases the area, demonstrating the continuity and orderly growth of the double-layer stacking; Figure 9 The above are the infrared Fourier spectra of three periodic bilayer samples from Example 1 of this invention, COO. - The paired peaks are stable at approximately 1605–1610 and 1413–1416 cm⁻¹. -1 The range further intensifies, from 1150 to 1000 cm. -1 The fingerprint area is raised overall, indicating that the coverage and network density are improved in tandem. Figure 10 The above are the infrared Fourier spectra of four periodic bilayer samples from Example 1 of this invention. COO - The Δν of the anti / symmetric peak and the I1600:I1415 ratio show significant changes in the lower period and tend to plateau, indicating that Ca 2+ It has a fully cross-linked, mature, layer-by-layer self-assembled structure and possesses the stability of a subsequent functionalized carrier; Figure 11 The infrared Fourier transform spectra of the four-cycle bilayer sample from Example 1 of this invention, which did not undergo calcium ion crosslinking and curing, show multilayer polysaccharide characteristics, but COO... - The peak position and intensity ratio of the anti / symmetric peaks did not reflect the systematic shift and redistribution induced by crosslinking, and Δν was small, clearly contrasting with Ca. 2+ The absence of an "egg-box" network demonstrates the necessity of the cross-linking step. Figure 12 This is the infrared Fourier transform spectrum of the sample after two-stage solid-state fermentation of a complex enzyme and probiotics immobilized in a multilayer polyelectrolyte network, as shown in Example 1 of the present invention. The spectrum is relative to the pre-crosslinking control amide I / II (approximately 1650 / 1545 cm⁻¹). -1 ) and lipid CH band (2920 / 2850 cm) -1 Enhanced and at 1575 / 1410 / 1045 cm -1 The presence of lactate-related uptake indicates that the active biological components and fermentation products were successfully introduced and maintained within the multilayer network. This is in summary due to the substrate—prepreg—expansion—layer-by-layer self-assembly and Ca... 2+ The consistent spectroscopic evidence throughout the cross-linking-functional loading process fully demonstrates the chemical rationality and process controllability of this scheme.

[0080] The performance of the examples and comparative examples is summarized in Table 1. In Comparative Example 1, the CO2 injection pressure was reduced to 0.3 MPa, resulting in insufficient foaming driving force. According to Henry's Law, the gas solubility decreased, and the pore structure became denser, reducing the specific surface area by about 25%, which in turn affected the enzyme loading efficiency and phosphorus release kinetics. In Comparative Examples 2-3, the temperature was reduced to 100°C and the moisture content was reduced to 8%, which were lower than the complete starch gelatinization temperature and the optimal plasticizing moisture content, respectively. According to the Arrhenius equation, the reaction rate decreased significantly, protein denaturation was insufficient, and the foaming effect was limited, resulting in uneven pore size distribution and decreased connectivity. In Comparative Examples 4-5, the improper setting of screw speed and residence time directly affected the shear rate and mixing uniformity. According to rheological theory, insufficient mechanical action led to structural defects and uneven component distribution. In Comparative Example 6, the number of polyelectrolyte layers was reduced to one cycle, which significantly reduced the membrane integrity and permeation barrier performance according to LbL self-assembly theory. The severely insufficient protective effect led to a significant decrease in enzyme activity stability and antioxidant performance. In Comparative Example 7, excessive Ca 2+ While excessive cross-linking (200 mmol / L) improves storage stability, it also hinders molecular mass transfer according to diffusion theory, reflecting the balance between cross-linking degree and functionality. In Comparative Examples 8-9, the improper ratio of polyelectrolyte solution concentration disrupted charge balance and interfacial chemical stability, affecting membrane uniformity and effective loading of functional molecules. In Comparative Examples 10-11, the significant reduction in probiotic inoculum amount and compound enzyme addition directly affected biocatalytic kinetics. According to the Michaelis-Menten equation, substrate conversion efficiency is positively correlated with enzyme concentration, leading to insufficient degradation of phytic acid phosphorus and a significant decrease in phosphorus utilization. In Comparative Example 12, the fermentation temperature was raised to 50°C, which exceeded the optimal growth temperature range for probiotics. According to the theory of microbial growth kinetics, this led to a decrease in strain activity and abnormal accumulation of metabolites. In Comparative Example 13, the excessive amount of natural deep eutectic solvent (8 wt.%) enhanced the pretreatment effect, but it may have resulted in residual solvent affecting the stability of subsequent processes and product quality. This reflects the trade-off between pretreatment intensity and process compatibility. Overall, all comparative examples were significantly inferior to the examples in core performance indicators such as phytic acid phosphorus degradation, phosphorus digestibility, enzyme and bacterial activity retention, and oxidative stability because the key process parameters deviated from the optimal window.

[0081] Table 1 Performance summary of the examples and comparative examples

[0082]

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A type of extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed, characterized in that, It has a multi-layered structure from the inside out, including: a) Porous expanded substrate: composed of rice bran, polished rice powder, and rice bran meal in a mass ratio of 0.9-1.1:0.9-1.1:0.9-1.1; formed into three-dimensional interconnected channels through CO2-guided expansion, foaming, and extrusion; the median pore size D50 is 20-60 μm, the proportion of interconnected pores is ≥60%, and the specific surface area is ≥1.0 m². 2 / g; b) Interface modification layer: covering the outer surface and pore walls of the substrate, formed by alternating deposition of sodium alginate and chitosan and cross-linking and curing with calcium ions to form a 2-6 cycle double-layer continuous multilayer polyelectrolyte network; c) Fermentation functional loading layer: A multi-layer polyelectrolyte network immobilizes a complex enzyme and probiotics. The amount of complex enzyme added is 100-1000 U / g (dry basis of the product), and the total inoculum amount of probiotics is 0.5%-5.0%. An active system is formed through two-stage solid-state fermentation, with phytase activity of 5000-10000 FTU / kg and a total viable count greater than or equal to 1×10⁻⁶. 8 CFU / g, wherein the probiotics are selected from one or more of the genera Bacillus and Lactobacillus.

2. The extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed as described in claim 1, characterized in that, The median pore size D50 of the porous expanded substrate is 25-50 μm.

3. The extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed as described in claim 1, characterized in that, The complex enzyme contains one or more of xylanase, β-glucanase, and mannanase.

4. The extruded, fermented, phosphorus-reduced, and highly digestible rice by-product feed as described in claim 1, characterized in that, When the rice by-product feed is stored at 25°C and 70% relative humidity for 90 days, the increase in acid value is less than or equal to 2 mg KOH / g, calculated based on the initial measurement value no more than 4 hours after preparation.

5. A method for preparing extruded fermented rice by-product feed with reduced phosphorus content and high digestibility as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1 involves pre-impregnating a mixture of rice bran, polished rice powder, and rice bran meal in a natural deep eutectic solvent and recovering the solvent. The natural deep eutectic solvent is composed of choline chloride, a hydrogen bond donor, and water. The hydrogen bond donor is selected from one or more of glycerol and lactic acid. S2 involves CO2-guided puffing and foaming extrusion of materials with a moisture content of 12%-16%. The first temperature zone is 90℃, the second temperature zone is 110℃, and the third temperature zone is 120-125℃. The CO2 injection pressure is 0.7-1.0MPa, and the injection mass ratio is 0.5%-1.0% (all on a dry basis). The residence time is 30-60s, resulting in a porous puffed substrate. The CO2 injection zone is located at the end of the second temperature zone or the beginning of the third temperature zone, and the screw speed is 250-380rpm. S3 undergoes layer-by-layer self-assembly after the discharged material is cooled to 35-40℃. Sodium alginate solution and chitosan solution are applied sequentially. The sodium alginate solution has a mass fraction of 0.2%-1.0% and a pH value of 6.0-7.5, while the chitosan solution has a mass fraction of 0.1%-0.5% and a pH value of 4.5-5.

5. The calcium chloride concentration is 10-100 mmol / L, and the single-step contact time is 30-180 s for each step. The resulting modified layer has a film thickness of 2-10 μm and a crosslinking degree of 0.5-1.0 mmol / g. S4 is loaded with compound enzymes and probiotics and undergoes two-stage solid-state fermentation. The first stage is carried out at a temperature of 40-42℃ for 18-24 hours, and the second stage is carried out at a temperature of 35-37℃ for 24-36 hours. The fermentation moisture content is 38%-42%, and the final pH value is 4.2-4.

8. The finished product is obtained after drying and sieving.

6. The method for preparing a high-digestibility, low-phosphorus rice by-product feed by extrusion and fermentation as described in claim 5, characterized in that, The natural deep eutectic solvent in step S1 is choline chloride:glycerol:water = 1:2:2, with a molar ratio of 2wt.%-5wt.% based on the dry basis of the raw materials. The pre-soaking temperature is 30-40 ℃, the time is 10-20 min, and the recovery rate is ≥90%.

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