Preparation process of manioc waste liquid feed based on microbial fermentation

Abstract

The invention provides a manioc waste liquid feed preparation process based on microbial fermentation, and belongs to the technical field of feed. According to the application, the nano calcium phosphate loaded high-valence ferric salt and the metal ion doped hydroxyapatite are introduced to solve the problems of excessive metal ions and anti-nutrient substance residues; the nano calcium phosphate loaded high-valence ferric salt efficiently oxidizes and removes cyanide ions and tannin in the fermentation liquor through ferrate loaded on the surface; oxidation products and part of ferric ions are fixed, so that inhibition on microorganisms is avoided; the metal ion-doped hydroxyapatite effectively captures excessive metal ions through ion exchange and complexation, reduces the free concentration of the metal ions, prevents adverse effects on microbial metabolism, can compete with anions in a fermentation liquid, inhibits the generation of toxic complexes, and reduces the toxicity to a fermentation system; the synergistic effect of removal of anti-nutrient substances and dynamic regulation and control of metal ions is achieved, and the nutritional value and safety of the final feed are improved.

Description

Technical Field

[0001] This invention belongs to the field of feed technology and relates to a preparation process of cassava residue liquid feed based on microbial fermentation. Background Technology

[0002] In the production of cassava residue liquid feed through microbial fermentation, the role of metal ions and their complexation with potential inhibitory factors are receiving increasing attention. Metal ions such as Fe... 3+ Cu 2+ Zn 2+ and Mn 2+ Metal ions are considered essential elements for microbial growth and metabolism, capable of activating related enzyme systems and promoting the initiation of specific metabolic pathways. However, excessive metal ions may not only inhibit microbial growth but also form complexes with substrates or byproducts, thereby affecting the efficiency of the fermentation process and the safety of the final feed. Furthermore, anti-nutritional substances that may remain in cassava residue, such as cyanide ions, tannins, and phytates, also pose a potential threat to animal health. Although these substances are partially degraded during processing, residues may still remain, affecting the safety and nutritional value of the feed.

[0003] Existing technologies have certain shortcomings in treating metal ions and anti-nutritional substances. First, while traditional materials such as clay-based materials (e.g., bentonite, zeolite, montmorillonite) have some capacity for ion exchange and adsorption, they perform poorly in terms of biocompatibility and nutrient supplementation, failing to meet the dual requirements of safety and nutritional value in liquid feed production. Second, although some research has been conducted on methods for removing or transforming anti-nutritional substances, current technologies often struggle to effectively remove or transform harmful substances resistant to microbial degradation without significantly damaging the nutritional components in the feed, resulting in compromised safety and quality of fermented products. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a preparation process for cassava residue liquid feed based on microbial fermentation. This application introduces nano-calcium phosphate loaded with ferric salts and hydroxyapatite doped with metal ions, aiming to simultaneously solve the negative effects caused by excessive metal ions and residual anti-nutrients. The nano-calcium phosphate loaded with ferric salts utilizes its surface-loaded ferrate to efficiently oxidize and remove cyanide ions and tannins from the fermentation broth, achieving the conversion of anti-nutrients. Simultaneously, the calcium phosphate matrix can immobilize oxidation products and some ferric ions through adsorption, avoiding their inhibitory effect on microorganisms. On the other hand, the hydroxyapatite doped with metal ions effectively captures excess metal ions through ion exchange and complexation, reducing their free concentration and thus preventing negative impacts on microbial metabolism. Furthermore, this material can compete with anions in the fermentation broth, inhibiting the formation of toxic complexes and reducing their toxicity to the fermentation system; by achieving a synergistic effect of anti-nutrient removal and dynamic regulation of metal ions, the chemical environment of the fermentation broth is improved, ensuring efficient microbial metabolism and simultaneously enhancing the nutritional value and safety of the final feed.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a process for preparing cassava residue liquid feed based on microbial fermentation, the process comprising:

[0007] Specifically, S1: Cassava residue is crushed and sieved, then mixed with ammonium chloride and water. The pH is adjusted to obtain a pre-fermentation broth. Calcium carbonate is added and microbial bacteria are inoculated to obtain a fermentation broth. Pre-fermentation is carried out at a constant temperature to obtain the first fermentation broth. During the second stirring during fermentation, hydroxyapatite doped with metal ions is added.

[0008] S2: Adjust the pH of the first fermentation liquid to obtain the second fermentation liquid. Add nano-calcium phosphate loaded with high-valent iron salt in batches to the second fermentation liquid and continue stirring to obtain the third fermentation liquid. Adjust the pH of the third fermentation liquid to obtain the fourth fermentation liquid. Continue fermentation and centrifuge to obtain cassava residue liquid feed based on microbial fermentation.

[0009] The preparation method of hydroxyapatite doped with metal ions is as follows:

[0010] Calcium nitrate, ferric nitrate, and magnesium chloride were dispersed in deionized water to obtain a mixed metal salt solution; diammonium hydrogen phosphate was dispersed in deionized water to obtain a phosphate solution, which was added dropwise to the mixed metal salt solution to obtain a mixed solution. The pH was adjusted to obtain reaction solution A. After reaction at a constant temperature, the solution was stirred and aged, filtered, washed, dried, and sieved to obtain hydroxyapatite doped with metal ions.

[0011] The preparation method of nano-calcium phosphate supported on high-valent iron salt is as follows:

[0012] Calcium nitrate solution and trisodium phosphate solution were prepared separately and mixed at a constant temperature. The pH was adjusted with ammonia water to obtain reaction solution B. The mixture was stirred and aged, centrifuged, washed, and dried to obtain the precursor. The precursor was calcined and ball-milled to obtain nano-calcium phosphate. The nano-calcium phosphate was dispersed in deionized water and ferric nitrate solution was added to obtain reaction solution C. The mixture was stirred and allowed to stand to obtain reaction solution D. The pH was adjusted and sodium hypochlorite solution was added to obtain reaction solution E. The mixture was stirred at a constant temperature, filtered, and dried to obtain nano-calcium phosphate loaded with high-valence iron salt.

[0013] In the production of cassava residue feed through microbial fermentation, metal ions and anti-nutritional substances are two key factors affecting fermentation efficiency and feed safety. Metal ions are essential elements for microbial growth and metabolism, activating relevant enzyme systems and promoting specific metabolic pathways. However, when the concentration of metal ions is too high, it not only inhibits the normal growth and metabolism of microorganisms but may also form complexes with fermentation substrates or byproducts, thereby reducing substrate conversion efficiency and generating toxic byproducts, affecting the safety of fermentation products. Furthermore, anti-nutritional substances that may remain in cassava residue (such as cyanide ions and tannins) can also negatively impact the fermentation process. Cyanide ions are highly toxic, inhibiting microbial metabolism and potentially contaminating the final feed; tannins interfere with the utilization of protein and minerals, significantly reducing the nutritional value of the feed. Although these anti-nutritional substances are partially degraded by microorganisms during fermentation, residual components may still pose a threat to the fermentation system and animal health.

[0014] To simultaneously address the issues of metal ion concentration control and anti-nutrient removal, the experiment introduced nano-calcium phosphate loaded with ferric salts and hydroxyapatite doped with metal ions. The nano-calcium phosphate loaded with ferric salts achieves efficient removal of anti-nutrients through the ferrate loaded on its surface. Ferrate, as a strong oxidant, has a high oxidation potential and can oxidize cyanide ions in the fermentation broth to low-toxicity isocyanates or further convert them into nitrogen gas, thereby reducing cyanide toxicity. Furthermore, ferrate can oxidize phenolic tannin molecules, initiating their polymerization reaction and transforming them into high-molecular-weight compounds that lose their ability to bind to proteins or minerals, thus weakening their anti-nutrient effect. The loading of ferrate on the surface of nano-calcium phosphate not only slows down the release rate of ferrate, avoiding excessive oxidative stress on the fermentation system, but also utilizes the adsorption capacity of the active sites on the calcium phosphate surface to capture byproducts of the oxidation reaction, fixing them through complexation or precipitation for subsequent separation.

[0015] If the ferric ions produced by the oxidation of ferrates are not fixed in time, they may lead to excessively high metal ion concentrations, inhibiting microorganisms and forming toxic complexes with anions such as sulfides and phosphates. To address this issue, nano-calcium phosphate partially fixes Fe through adsorption and precipitation.3+ Furthermore, this application introduces hydroxyapatite doped with metal ions to enhance the dynamic control capability of metal ions. Hydroxyapatite is an inorganic material with strong ion exchange capacity; in its crystal structure, Ca... 2+ When partially replaced by other metal ions, it can form doped hydroxyapatite. The doping design involves introducing Fe... 3+ Mg 2+ The addition of metal ions not only enhances the stability of hydroxyapatite but also improves its ability to immobilize target metal ions. In the fermentation system, metal-doped hydroxyapatite captures excess metal ions, such as Fe generated after oxidation, through ion exchange and complexation. 3+ Other excess Cu 2+ Zn 2+ The doped hydroxyapatite can also competitively complex with anions such as phosphate, sulfide, and ammonia nitrogen in the fermentation broth, inhibiting the formation of toxic complexes and thus reducing their toxicity to the fermentation system.

[0016] By combining nano-calcium phosphate loaded with ferric salts and hydroxyapatite doped with metal ions, a synergistic mechanism is formed. The nano-calcium phosphate loaded with ferric salts removes anti-nutritional substances through the oxidative degradation of ferrates. Simultaneously, the calcium phosphate matrix adsorbs oxidation products and immobilizes some ferric ions, while the hydroxyapatite doped with metal ions further immobilizes excess metal ions through ion exchange, preventing toxicity problems caused by excessive metal ion concentration. This combination not only effectively removes anti-nutritional substances and improves the chemical environment of the fermentation broth, but also maintains the balance of the fermentation system through dynamic metal ion regulation, ensuring efficient microbial metabolism. Furthermore, these materials can slowly release nutrients such as calcium and phosphorus, improving the nutritional value and safety of the final feed. This multifunctional material design provides a scientific and effective solution for optimizing cassava residue fermentation systems.

[0017] As a preferred technical solution of the present invention, in step S1, the mass ratio of cassava residue to ammonium chloride is 100:3-5, for example, it can be 100:3, 100:3.2, 100:3.4, 100:3.6, 100:3.8, 100:4.0, 100:4.2, 100:4.4, 100:4.6, 100:4.8 or 100:5, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0018] In some alternative embodiments, the cassava residue is crushed, sieved, and then mixed with ammonium chloride and water to adjust the pH to 6.5-7. For example, it can be 6.5, 6.55, 6.6, 6.65, 6.7, 6.75, 6.8, 6.85, 6.9, 6.95, or 7, but is not limited to such values. Values ​​not mentioned in this range are also applicable.

[0019] In some optional embodiments, the solid content in the pre-fermentation broth is 30-35%, for example, it can be 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5% or 35%, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0020] In some optional embodiments, the amount of calcium carbonate fed is 2-5 g / L, for example, it can be 2 g / L, 2.3 g / L, 2.6 g / L, 2.9 g / L, 3.2 g / L, 3.5 g / L, 3.8 g / L, 4.1 g / L, 4.4 g / L, 4.7 g / L or 5 g / L, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0021] This application incorporates calcium carbonate, specifying its dosage as 2-5 g / L. Calcium carbonate primarily functions as a buffer and replenishes calcium ions in the fermentation system. During fermentation, microbial metabolism typically produces organic acids, leading to a decrease in the pH of the fermentation broth. If the pH is too low, it inhibits microbial activity and affects the normal function of enzymes. Calcium carbonate, as a weakly alkaline buffer, can react with organic acids, gradually releasing carbonate and calcium ions, thus neutralizing acidity and maintaining pH stability. Furthermore, the calcium carbonate releases calcium... 2+ It not only provides the necessary metal ions for microbial growth, but also combines with phosphate ions in the fermentation broth to form calcium phosphate microprecipitates, further regulating the balance of metal ions. Limiting the feed amount to 2-5 g / L is to avoid excessive use of calcium carbonate leading to overly alkaline conditions that inhibit microbial metabolic activity, while ensuring a moderate calcium ion concentration to prevent excessive precipitation that could affect the uniformity of the fermentation broth.

[0022] The microorganisms are lactic acid bacteria and yeast;

[0023] In some alternative embodiments, the inoculation amount of the microorganism is 5-10% of the mass of the pre-fermentation broth, for example, it can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0024] In some optional embodiments, the temperature of the initial fermentation of the fermentation broth is 30-35°C, for example, 30°C, 30.5°C, 31°C, 31.5°C, 32°C, 32.5°C, 33°C, 33.5°C, 34°C, 34.5°C or 35°C, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0025] In some optional embodiments, the initial fermentation time of the fermentation broth is 24-30 hours, for example, 24 hours, 24.6 hours, 25.2 hours, 25.8 hours, 26.4 hours, 27 hours, 27.6 hours, 28.2 hours, 28.8 hours, 29.4 hours, or 30 hours, but is not limited to such values. Values ​​not mentioned in this range are also applicable.

[0026] In some alternative embodiments, the fermentation broth is stirred once every 4-6 hours during the early fermentation period, for example, 4h, 4.2h, 4.4h, 4.6h, 4.8h, 5.0h, 5.2h, 5.4h, 5.6h, 5.8h or 6h, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0027] In some optional embodiments, the fermentation broth is stirred once for 10-15 minutes during the early fermentation stage, for example, 10 minutes, 10.5 minutes, 11 minutes, 11.5 minutes, 12 minutes, 12.5 minutes, 13 minutes, 13.5 minutes, 14 minutes, 14.5 minutes or 15 minutes, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0028] Hydroxyapatite doped with metal ions was added during the second stirring of the fermentation broth in the early stage of fermentation.

[0029] This application specifically specifies the addition of metal-doped hydroxyapatite during the second stirring stage in the early fermentation phase. In the early stages of fermentation, microorganisms rapidly adapt to the environment and begin to grow, at which point their demand for metal ions is high, while the concentration of metal ions in the fermentation broth has not yet significantly accumulated. During the second stirring, the metal ions in the fermentation broth gradually accumulate due to microbial metabolism, potentially reaching inhibitory levels. Adding metal-doped hydroxyapatite at this time can effectively capture excess metal ions through ion exchange and complexation, preventing excessively high free concentrations from causing toxic effects on microorganisms. Furthermore, the metal-doped hydroxyapatite can slowly release the doped metal ions, providing adequate trace elements for the activation of key enzyme systems, thereby supporting the initiation of subsequent metabolic pathways and maintaining the balance of the fermentation system.

[0030] In some optional embodiments, the amount of hydroxyapatite doped with metal ions is 0.3-0.5% of the mass of the fermentation broth, for example, it can be 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.40%, 0.42%, 0.44%, 0.46%, 0.48% or 0.5%, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0031] As a preferred technical solution of the present invention, in step S2, the pH of the first fermentation broth is adjusted to 8.5-9, for example, it can be 8.5, 8.55, 8.6, 8.65, 8.7, 8.75, 8.8, 8.85, 8.9, 8.95 or 9, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0032] The pH of the first fermentation broth was adjusted using a 2% sodium bicarbonate solution, with an adjustment of 0.2 units every 1 hour for the first two adjustments, and 0.3 units every 3 hours thereafter.

[0033] This application specifies the use of a sodium bicarbonate solution gradient to adjust the pH of the first fermentation broth. This method balances the chemical regulation of the fermentation broth and the metabolic adaptation of the microorganisms, ensuring the stability and efficiency of the fermentation system throughout the process. The strategy of slowly increasing the pH by 0.2 units every 1 hour in the first two stages is mainly to allow the microorganisms to gradually adapt to the pH changes. The microorganisms in the fermentation broth are very sensitive to environmental changes; excessively rapid pH adjustments may cause metabolic stress, leading to decreased enzyme activity or inhibited microbial proliferation. Therefore, providing the microorganisms with adaptation time through small-scale adjustments in the initial stage can maintain their normal physiological metabolism.

[0034] After the pH of the fermentation broth gradually approaches the neutral or alkaline range, the adjustment method is changed to 0.3 units every 3 hours. This is based on the characteristic that the acid buffering capacity of the fermentation broth gradually decreases under alkaline conditions. At this point, the microorganisms have adapted to the higher pH environment, the production rate of acidic metabolites slows down, and the need for pH adjustment decreases. By extending the adjustment interval and increasing the adjustment range, the pH of the fermentation broth can be raised to the target range more efficiently, while avoiding the problem of increased salt concentration caused by excessive sodium bicarbonate accumulation.

[0035] This application specifies that the pH of the first fermentation broth is adjusted to 8.5-9 to obtain the second fermentation broth, and then nano-calcium phosphate loaded with ferric salt is added. The purpose is to provide a suitable environment for the optimal activity of the nano-calcium phosphate loaded with ferric salt. Ferrate exhibits high stability under alkaline conditions, allowing it to fully exert its ability to oxidize and degrade anti-nutrients. Simultaneously, the alkaline environment helps calcium phosphate adsorb oxidized byproducts, fixing them through precipitation and preventing them from interfering with subsequent fermentation processes. Furthermore, the pH range of 8.5-9 falls within the activity window of ferrate without excessively inhibiting the physiological metabolism of the fermenting microorganisms.

[0036] In some optional embodiments, the amount of nano-calcium phosphate loaded with high-valence iron salt is 0.1-0.2% of the mass of the first fermentation broth, for example, it can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19% or 0.2%, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0037] In some optional embodiments, after adding nano-calcium phosphate loaded with high-valent iron salt to the second fermentation broth, the reaction is stirred for 6-12 hours, for example, 6 hours, 6.6 hours, 7.2 hours, 7.8 hours, 8.4 hours, 9 hours, 9.6 hours, 10.2 hours, 10.8 hours, 11.4 hours or 12 hours, but not limited to such values, and values ​​not mentioned in this range are also applicable.

[0038] In some alternative embodiments, the pH of the third fermentation broth is adjusted to 6.5-7 to obtain a fourth fermentation broth, for example, 6.5, 6.55, 6.6, 6.65, 6.7, 6.75, 6.8, 6.85, 6.9, 6.95 or 7, but not limited to such values, and values ​​not mentioned in this range are also applicable.

[0039] This application specifies that the pH of the third fermentation broth be adjusted back to 6.5-7 to obtain the fourth fermentation broth in order to restore optimal growth conditions for microorganisms. Most fermentation microorganisms exhibit the highest activity in neutral or slightly acidic environments. While alkaline environments are beneficial for the oxidation of ferrates, they may inhibit microbial metabolism. By adjusting the pH back to 6.5-7, the metabolic activity of microorganisms can be reactivated, promoting the subsequent fermentation process. Furthermore, a neutral pH also contributes to the stability of the fermentation broth, preventing further precipitation or sedimentation of metal ions under alkaline conditions from affecting fermentation efficiency.

[0040] In some alternative embodiments, the fourth fermentation broth continues to ferment for 1-2 days, for example, 1 day, 1.1 days, 1.2 days, 1.3 days, 1.4 days, 1.5 days, 1.6 days, 1.7 days, 1.8 days, 1.9 days, or 2 days, but is not limited to such values, and values ​​not mentioned in this range also apply.

[0041] As a preferred technical solution of the present invention, in the preparation method of hydroxyapatite doped with metal ions, the molar ratio of calcium nitrate, ferric nitrate and magnesium chloride in the mixed metal salt solution is (0.5-0.6):(0.025-0.03):(0.025-0.03).

[0042] In some alternative embodiments, the concentration of calcium nitrate in the mixed metal salt solution is 0.8-1.2M, for example, 0.8M, 0.84M, 0.88M, 0.92M, 0.96M, 1M, 1.04M, 1.08M, 1.12M, 1.16M or 1.2M, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0043] The molar ratio of calcium nitrate to diammonium hydrogen phosphate is (0.5-0.6):(0.3-0.4).

[0044] In some alternative embodiments, the concentration of the phosphate solution is 0.5-0.8M, for example, 0.5M, 0.53M, 0.56M, 0.59M, 0.62M, 0.65M, 0.68M, 0.71M, 0.74M, 0.77M or 0.8M, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0045] In some alternative embodiments, the phosphate solution is added dropwise to the mixed metal salt solution at a rate of 2-3 mL / min, for example, 2 mL / min, 2.1 mL / min, 2.2 mL / min, 2.3 mL / min, 2.4 mL / min, 2.5 mL / min, 2.6 mL / min, 2.7 mL / min, 2.8 mL / min, 2.9 mL / min or 3 mL / min, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0046] In some alternative embodiments, the pH of the mixture is adjusted to 9.5-10 to obtain reaction solution A, for example, 9.5, 9.55, 9.6, 9.65, 9.7, 9.75, 9.8, 9.85, 9.9, 9.95 or 10, but not limited to such values, and values ​​not mentioned in this range are also applicable.

[0047] In some optional embodiments, the isothermal reaction temperature of the reaction solution A is 140-160°C, for example, it can be 140°C, 142°C, 144°C, 146°C, 148°C, 150°C, 152°C, 154°C, 156°C, 158°C or 160°C, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0048] In some alternative embodiments, the reaction time of the reaction solution A at a constant temperature is 2-3 hours, for example, 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3 hours, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0049] This application specifies the temperature and time for the isothermal reaction in reaction solution A. The isothermal reaction conditions (140-160℃, 2-3h) are a crucial step in the preparation of metal-doped hydroxyapatite. The isothermal reaction provides sufficient energy to promote uniform doping of metal ions into the hydroxyapatite lattice while ensuring the integrity of the hydroxyapatite's crystal structure. Within a suitable temperature range, the reaction rate and crystal growth rate reach equilibrium, resulting in metal-doped hydroxyapatite with high purity and stability. Limiting the reaction time to 2-3h avoids over-reaction that could lead to crystal defects or impurities.

[0050] In some optional embodiments, the reaction solution A is reacted at a constant temperature and then stirred and aged for 20-24 hours, for example, 20 hours, 20.4 hours, 20.8 hours, 21.2 hours, 21.6 hours, 22 hours, 22.4 hours, 22.8 hours, 23.2 hours, 23.6 hours or 24 hours, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0051] As a preferred technical solution of the present invention, in the preparation method of nano-calcium phosphate loaded with high-valent iron salt, the calcium nitrate solution and trisodium phosphate solution are mixed at 60-70°C, for example, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but are not limited to such values, and values ​​not mentioned in this range are also applicable.

[0052] In some alternative embodiments, the molar ratio of calcium nitrate to trisodium phosphate is 1.2-1.4:1, for example, it can be 1.2:1, 1.22:1, 1.24:1, 1.26:1, 1.28:1, 1.3:1, 1.32:1, 1.34:1, 1.36:1, 1.38:1 or 1.4:1, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0053] In some alternative embodiments, the calcium nitrate solution and trisodium phosphate solution are mixed and the pH is adjusted to 8.5-9 with ammonia to obtain reaction solution B. For example, the pH can be 8.5, 8.55, 8.6, 8.65, 8.7, 8.75, 8.8, 8.85, 8.9, 8.95 or 9, but is not limited to such values. Values ​​not mentioned in this range are also applicable.

[0054] In some optional embodiments, the reaction solution B is stirred and aged for 10-12 hours, for example, 10 hours, 10.2 hours, 10.4 hours, 10.6 hours, 10.8 hours, 11 hours, 11.2 hours, 11.4 hours, 11.6 hours, 11.8 hours or 12 hours, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0055] In some optional embodiments, the precursor is calcined at a temperature of 775-785°C, for example, 775°C, 776°C, 777°C, 778°C, 779°C, 780°C, 781°C, 782°C, 783°C, 784°C or 785°C, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0056] In some alternative embodiments, the calcination time of the precursor is 4-5 hours, for example, 4 hours, 4.1 hours, 4.2 hours, 4.3 hours, 4.4 hours, 4.5 hours, 4.6 hours, 4.7 hours, 4.8 hours, 4.9 hours, or 5 hours, but is not limited to such values. Values ​​not mentioned in this range are also applicable.

[0057] This application specifies the calcination temperature and time for the precursor. The calcination conditions (780±5℃, 4-5h) are crucial for the preparation of nano-calcium phosphate. The calcination process at high temperature promotes the dehydration, decomposition, and crystal reconstruction of the precursor, generating nano-calcium phosphate with good crystallinity and stability. The calcination temperature of 780℃ avoids the formation of thermally unstable calcium phosphate at high temperatures. The calcination time of 4-5h ensures complete reaction while avoiding excessively long calcination that could lead to particle agglomeration or excessive crystal growth, affecting the nanoscale properties of the final material. Subsequent ball milling further optimizes the particle size and specific surface area of ​​the calcium phosphate, providing sufficient active surface for loading ferrates.

[0058] In some optional embodiments, the particle size of the nano-calcium phosphate is 100-200 nm, for example, it can be 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm or 200 nm, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0059] In some optional embodiments, the mass ratio of the nano-calcium phosphate to deionized water is (40-50):200, for example, it can be 40:200, 41:200, 42:200, 43:200, 44:200, 45:200, 46:200, 47:200, 48:200, 49:200 or 50:200, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0060] In some optional embodiments, the mass ratio of ferric nitrate to nano-calcium phosphate in the reaction solution C is 3-4:100, for example, it can be 3:100, 3.1:100, 3.2:100, 3.3:100, 3.4:100, 3.5:100, 3.6:100, 3.7:100, 3.8:100, 3.9:100 or 4:100, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0061] In some optional embodiments, the reaction solution C is stirred for 50-60 minutes, for example, 50 minutes, 51 minutes, 52 minutes, 53 minutes, 54 minutes, 55 minutes, 56 minutes, 57 minutes, 58 minutes, 59 minutes or 60 minutes, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0062] In some optional embodiments, reaction solution C is stirred and then allowed to stand for 2-3 hours to obtain reaction solution D. For example, it can be 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3 hours, but is not limited to such values. Values ​​not mentioned in this range are also applicable.

[0063] In some alternative embodiments, the pH of the reaction solution D is adjusted to 10-11, for example, it can be 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9 or 11, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0064] In some optional embodiments, after adjusting the pH of the reaction solution D, a sodium hypochlorite solution with a mass fraction of 10-15 wt.% is added, for example, 10 wt.%, 10.5 wt.%, 11 wt.%, 11.5 wt.%, 12 wt.%, 12.5 wt.%, 13 wt.%, 13.5 wt.%, 14 wt.%, 14.5 wt.%, or 15 wt.%, but is not limited to such values; values ​​not mentioned within this range are also applicable.

[0065] In some alternative embodiments, the molar ratio of sodium hypochlorite to ferric nitrate is (4.5-5):2, for example, it can be 4.5:2, 4.55:2, 4.6:2, 4.65:2, 4.7:2, 4.75:2, 4.8:2, 4.85:2, 4.9:2, 4.95:2 or 5:2, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0066] In some optional embodiments, the temperature of the reaction solution E under constant temperature stirring is 30-40°C, for example, it can be 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C or 40°C, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0067] In some optional embodiments, the reaction solution E is stirred at a constant temperature for 30-40 minutes, for example, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, 35 minutes, 36 minutes, 37 minutes, 38 minutes, 39 minutes or 40 minutes, but is not limited to such values, and values ​​not mentioned in this range are also applicable.

[0068] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0069] This application utilizes nano-calcium phosphate loaded with ferric salts, leveraging the strong oxidizing power of ferrates and the adsorption capacity of nano-calcium phosphates to achieve highly efficient removal of residual anti-nutritional substances from cassava residue. This treatment method effectively improves the chemical environment quality of the fermentation broth, ensures the metabolic activity of fermentation microorganisms, and significantly reduces the potential toxicity risk to livestock from the final feed.

[0070] This application utilizes hydroxyapatite doped with metal ions to capture and fix excess metal ions, as well as Fe generated after oxidation of ferrates. 3+ This avoids the inhibitory effect of excessively high metal ion concentrations on microorganisms. Furthermore, hydroxyapatite doped with metal ions can slowly release the doped Fe... 3+ Mg 2+ Trace elements provide essential metal ions for microbial metabolism, ensuring the activation of key enzyme systems and the normal functioning of metabolic pathways. This dynamic regulation mechanism effectively mitigates the toxic effects caused by fluctuations in metal ion concentration while maintaining the stability of the fermentation system.

[0071] This application significantly reduces the toxicity risk in fermented feed by removing anti-nutritional substances and regulating metal ion concentration. Furthermore, hydroxyapatite doped with metal ions and nano-calcium phosphate loaded with high-valence iron salts can slowly release nutrients such as calcium and phosphorus during fermentation, further enhancing the mineral content and nutritional value of the feed, making it more suitable for the growth needs of livestock; and the materials used have high biocompatibility and environmental friendliness, ultimately preventing pollution of the feed or the environment. Detailed Implementation

[0072] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include technical solutions that employ any obvious substitutions and modifications made to the embodiments described herein.

[0073] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone further purification or processing.

[0074] Example 1

[0075] This embodiment provides a preparation process for cassava residue liquid feed based on microbial fermentation. The preparation process specifically includes the following steps:

[0076] S1: Crush and sieve cassava residue, mix it with ammonium chloride and water, and adjust the pH to 6.8 to obtain a pre-fermentation broth. The mass ratio of cassava residue to ammonium chloride is 100:4, and the solid content of the pre-fermentation broth is 32%. Add calcium carbonate, inoculate with microorganisms such as lactic acid bacteria and yeast to obtain a fermentation broth. The amount of calcium carbonate added is 4 g / L, and the amount of microorganisms inoculated is 8% of the mass of the pre-fermentation broth. The first fermentation broth is obtained by pre-fermentation at a constant temperature of 32℃ for 28 hours. During this period, stir once every 5.5 hours for 12 minutes each time. When stirring for the second time, add 0.45% of the mass of the fermentation broth containing hydroxyapatite doped with metal ions.

[0077] S2: Adjust the pH of the first fermentation broth to 8.8 to obtain the second fermentation broth. Use 2% sodium bicarbonate solution to adjust the pH, adjusting by 0.2 units every 1 hour for the first two times, and by 0.3 units every 3 hours thereafter. Add 0.15% of the mass of the first fermentation broth of nano-calcium phosphate loaded with high-valence iron salt in batches to the second fermentation broth, and continue stirring and reacting for 10 hours to obtain the third fermentation broth. Adjust the pH of the third fermentation broth back to 6.8 to obtain the fourth fermentation broth, continue fermentation for 1.5 days, centrifuge, and you will get the cassava residue liquid feed based on microbial fermentation.

[0078] The preparation method of hydroxyapatite doped with metal ions is as follows:

[0079] 0.58 mol calcium nitrate, 0.028 mol ferric nitrate, and 0.025 mol magnesium chloride were dispersed in deionized water to obtain a mixed metal salt solution, wherein the concentration of calcium nitrate in the mixed metal salt solution was 1 M. 0.35 mol diammonium hydrogen phosphate was dispersed in deionized water to obtain a phosphate solution with a concentration of 0.7 M. This phosphate solution was added dropwise to the mixed metal salt solution at a rate of 2.8 mL / min to obtain a mixed solution. The pH was adjusted to 9.8 to obtain reaction solution A. The reaction was carried out at a constant temperature of 150 °C for 2.8 h, followed by stirring and aging for 22 h. The solution was then filtered, washed, dried, and sieved to obtain hydroxyapatite doped with metal ions.

[0080] The preparation method of nano-calcium phosphate supported on high-valent iron salt is as follows:

[0081] Calcium nitrate solution and trisodium phosphate solution were prepared separately and mixed at 67℃, with a molar ratio of calcium nitrate to trisodium phosphate of 1.3:1. The pH was adjusted to 8.5 with ammonia water to obtain reaction solution B. The mixture was stirred and aged for 11.5 h, centrifuged, washed, and dried to obtain the precursor. The precursor was calcined at 775℃ for 4.5 h and ball-milled to obtain nano-calcium phosphate with a particle size of 150 nm. 48 g of nano-calcium phosphate was dispersed in 200 mL of deionized water, and ferric nitrate solution was added to obtain reaction solution C, with a mass ratio of ferric nitrate to nano-calcium phosphate of 3.5:100. The mixture was stirred for 58 min and then allowed to stand for 2 h to obtain reaction solution D. The pH was adjusted to 10.5, and 13 wt.% sodium hypochlorite solution was added to obtain reaction solution E, with a molar ratio of sodium hypochlorite to ferric nitrate of 4.5:2. The mixture was stirred at a constant temperature of 33℃ for 40 min, filtered, and dried to obtain nano-calcium phosphate loaded with high-valence iron salt.

[0082] Example 2

[0083] This embodiment provides a preparation process for cassava residue liquid feed based on microbial fermentation. The preparation process specifically includes the following steps:

[0084] S1: Crush and sieve cassava residue, mix it with ammonium chloride and water, and adjust the pH to 6.6 to obtain a pre-fermentation broth. The mass ratio of cassava residue to ammonium chloride is 100:4.5, and the solid content of the pre-fermentation broth is 34%. Add calcium carbonate, inoculate with microorganisms such as lactic acid bacteria and yeast to obtain a fermentation broth. The amount of calcium carbonate added is 2g / L, and the amount of microorganisms inoculated is 5% of the mass of the pre-fermentation broth. The first fermentation broth is obtained by pre-fermentation at a constant temperature of 33℃ for 26 hours. During the first fermentation, stir once every 4 hours for 14 minutes each time. When stirring for the second time, add 0.3% of the mass of the fermentation broth containing hydroxyapatite doped with metal ions.

[0085] S2: Adjust the pH of the first fermentation broth to 8.7 to obtain the second fermentation broth. Use 2% sodium bicarbonate solution to adjust the pH, adjusting by 0.2 units every 1 hour for the first two times, and by 0.3 units every 3 hours thereafter. Add 0.18% of the mass of the first fermentation broth of nano-calcium phosphate loaded with high-valence iron salt in batches to the second fermentation broth, and continue stirring and reacting for 6 hours to obtain the third fermentation broth. Adjust the pH of the third fermentation broth back to 6.6 to obtain the fourth fermentation broth. Continue fermentation for 1 day, centrifuge, and you will get the cassava residue liquid feed based on microbial fermentation.

[0086] The preparation method of hydroxyapatite doped with metal ions is as follows:

[0087] 0.55 mol calcium nitrate, 0.027 mol ferric nitrate, and 0.028 mol magnesium chloride were dispersed in deionized water to obtain a mixed metal salt solution, wherein the concentration of calcium nitrate in the mixed metal salt solution was 1.1 M. 0.38 mol diammonium hydrogen phosphate was dispersed in deionized water to obtain a phosphate solution with a concentration of 0.5 M. The phosphate solution was added dropwise to the mixed metal salt solution at a rate of 2.7 mL / min to obtain a mixed solution. The pH was adjusted to 9.7 to obtain reaction solution A. The reaction was carried out at a constant temperature of 156 °C for 2 h, and then stirred and aged for 23 h. The solution was filtered, washed, dried, and sieved to obtain hydroxyapatite doped with metal ions.

[0088] The preparation method of nano-calcium phosphate supported on high-valent iron salt is as follows:

[0089] Calcium nitrate solution and trisodium phosphate solution were prepared separately and mixed at 65℃, with a molar ratio of calcium nitrate to trisodium phosphate of 1.35:1. The pH was adjusted to 8.8 with ammonia water to obtain reaction solution B. The mixture was stirred and aged for 10 h, centrifuged, washed, and dried to obtain the precursor. The precursor was calcined at 782℃ for 4.8 h and ball-milled to obtain nano-calcium phosphate with a particle size of 180 nm. 45 g of nano-calcium phosphate was dispersed in 200 mL of deionized water, and ferric nitrate solution was added to obtain reaction solution C, with a mass ratio of ferric nitrate to nano-calcium phosphate of 3.8:100. The mixture was stirred for 50 min and then allowed to stand for 3 h to obtain reaction solution D. The pH was adjusted to 10, and 10 wt.% sodium hypochlorite solution was added to obtain reaction solution E, with a molar ratio of sodium hypochlorite to ferric nitrate of 5:2. The mixture was stirred at a constant temperature of 37℃ for 34 min, filtered, and dried to obtain nano-calcium phosphate loaded with high-valence iron salt.

[0090] Example 3

[0091] This embodiment provides a preparation process for cassava residue liquid feed based on microbial fermentation. The preparation process specifically includes the following steps:

[0092] S1: Crush and sieve cassava residue, mix it with ammonium chloride and water, and adjust the pH to 6.5 to obtain a pre-fermentation broth. The mass ratio of cassava residue to ammonium chloride is 100:3, and the solid content of the pre-fermentation broth is 30%. Add calcium carbonate, inoculate with microorganisms such as lactic acid bacteria and yeast to obtain a fermentation broth. The amount of calcium carbonate added is 3g / L, and the amount of microorganisms inoculated is 7% of the mass of the pre-fermentation broth. The first fermentation broth is obtained by pre-fermentation at a constant temperature of 30℃ for 24 hours. During this period, stir once every 5 hours for 10 minutes each time. When stirring for the second time, add 0.4% of the mass of the fermentation broth containing hydroxyapatite doped with metal ions.

[0093] S2: Adjust the pH of the first fermentation broth to 8.5 to obtain the second fermentation broth. Use 2% sodium bicarbonate solution to adjust the pH, adjusting by 0.2 units every 1 hour for the first two times, and by 0.3 units every 3 hours thereafter. Add 0.1% of the mass of the first fermentation broth of nano-calcium phosphate loaded with high-valence iron salt in batches to the second fermentation broth, and continue stirring and reacting for 8 hours to obtain the third fermentation broth. Adjust the pH of the third fermentation broth back to 6.5 to obtain the fourth fermentation broth. Continue fermentation for 2 days, centrifuge, and you will get the cassava residue liquid feed based on microbial fermentation.

[0094] The preparation method of hydroxyapatite doped with metal ions is as follows:

[0095] 0.5 mol calcium nitrate, 0.025 mol ferric nitrate, and 0.026 mol magnesium chloride were dispersed in deionized water to obtain a mixed metal salt solution, wherein the concentration of calcium nitrate in the mixed metal salt solution was 0.8 M. 0.3 mol diammonium hydrogen phosphate was dispersed in deionized water to obtain a phosphate solution with a concentration of 0.8 M. The phosphate solution was added dropwise to the mixed metal salt solution at a rate of 2 mL / min to obtain a mixed solution. The pH was adjusted to 9.5 to obtain reaction solution A. The reaction was carried out at a constant temperature of 140 °C for 2.5 h, and then stirred and aged for 20 h. The solution was filtered, washed, dried, and sieved to obtain hydroxyapatite doped with metal ions.

[0096] The preparation method of nano-calcium phosphate supported on high-valent iron salt is as follows:

[0097] Calcium nitrate solution and trisodium phosphate solution were prepared separately and mixed at 60℃, with a molar ratio of calcium nitrate to trisodium phosphate of 1.2:1. The pH was adjusted to 8.7 with ammonia water to obtain reaction solution B. The mixture was stirred and aged for 11 h, centrifuged, washed, and dried to obtain the precursor. The precursor was calcined at 780℃ for 4 h and ball-milled to obtain nano-calcium phosphate with a particle size of 100 nm. 40 g of nano-calcium phosphate was dispersed in 200 mL of deionized water, and ferric nitrate solution was added to obtain reaction solution C, with a mass ratio of ferric nitrate to nano-calcium phosphate of 4:100. The mixture was stirred for 60 min and allowed to stand for 2.5 h to obtain reaction solution D. The pH was adjusted to 11, and 15 wt.% sodium hypochlorite solution was added to obtain reaction solution E, with a molar ratio of sodium hypochlorite to ferric nitrate of 4.8:2. The mixture was stirred at a constant temperature of 30℃ for 38 min, filtered, and dried to obtain nano-calcium phosphate loaded with high-valence iron salt.

[0098] Example 4

[0099] This embodiment provides a preparation process for cassava residue liquid feed based on microbial fermentation. The preparation process specifically includes the following steps:

[0100] S1: Crush and sieve the cassava residue, mix it with ammonium chloride and water, and adjust the pH to 7 to obtain the pre-fermentation liquid. The mass ratio of cassava residue to ammonium chloride is 100:5, and the solid content of the pre-fermentation liquid is 35%. Add calcium carbonate, inoculate with microorganisms such as lactic acid bacteria and yeast to obtain the fermentation liquid. The amount of calcium carbonate added is 5g / L, and the amount of microorganisms inoculated is 10% of the mass of the pre-fermentation liquid. The first fermentation liquid is obtained by pre-fermentation at a constant temperature of 35℃ for 30h. During this period, stir once every 6h for 15min each time. When stirring for the second time, add 0.5% of the mass of the fermentation liquid doped with metal ions, hydroxyapatite.

[0101] S2: Adjust the pH of the first fermentation broth to 9 to obtain the second fermentation broth. Use 2% sodium bicarbonate solution to adjust the pH, adjusting by 0.2 units every 1 hour for the first two times, and by 0.3 units every 3 hours thereafter. Add 0.2% of the mass of the first fermentation broth of nano-calcium phosphate loaded with high-valence iron salt in batches to the second fermentation broth, and continue stirring and reacting for 12 hours to obtain the third fermentation broth. Adjust the pH of the third fermentation broth back to 7 to obtain the fourth fermentation broth, continue fermentation for 1.7 days, and centrifuge to obtain the cassava residue liquid feed based on microbial fermentation.

[0102] The preparation method of hydroxyapatite doped with metal ions is as follows:

[0103] 0.6 mol calcium nitrate, 0.03 mol ferric nitrate, and 0.03 mol magnesium chloride were dispersed in deionized water to obtain a mixed metal salt solution, wherein the concentration of calcium nitrate in the mixed metal salt solution was 1.2 M. 0.4 mol diammonium hydrogen phosphate was dispersed in deionized water to obtain a phosphate solution with a concentration of 0.6 M. The phosphate solution was added dropwise to the mixed metal salt solution at a rate of 3 mL / min to obtain a mixed solution. The pH was adjusted to 10 to obtain reaction solution A. The reaction was carried out at a constant temperature of 160 °C for 3 h, and then stirred and aged for 24 h. The solution was filtered, washed, dried, and sieved to obtain hydroxyapatite doped with metal ions.

[0104] The preparation method of nano-calcium phosphate supported on high-valent iron salt is as follows:

[0105] Calcium nitrate solution and trisodium phosphate solution were prepared separately and mixed at 70℃, with a molar ratio of calcium nitrate to trisodium phosphate of 1.4:1. The pH was adjusted to 9 with ammonia water to obtain reaction solution B. The mixture was stirred and aged for 12 h, centrifuged, washed, and dried to obtain the precursor. The precursor was calcined at 785℃ for 5 h and ball-milled to obtain nano-calcium phosphate with a particle size of 200 nm. 50 g of nano-calcium phosphate was dispersed in 200 mL of deionized water, and ferric nitrate solution was added to obtain reaction solution C, with a mass ratio of ferric nitrate to nano-calcium phosphate of 3:100. The mixture was stirred for 55 min and then allowed to stand for 2.8 h to obtain reaction solution D. The pH was adjusted to 10.8, and 14 wt.% sodium hypochlorite solution was added to obtain reaction solution E, with a molar ratio of sodium hypochlorite to ferric nitrate of 4.7:2. The mixture was stirred at a constant temperature of 40℃ for 30 min, filtered, and dried to obtain nano-calcium phosphate loaded with high-valence iron salt.

[0106] Comparative Example 1

[0107] This comparative example provides a preparation process for cassava residue liquid feed based on microbial fermentation. The difference from Example 1 is that in S1, no hydroxyapatite with doped metal ions is added, while the other operation steps and process parameters are exactly the same as in Example 1.

[0108] Comparative Example 2

[0109] This comparative example provides a preparation process for cassava residue liquid feed based on microbial fermentation. The difference from Example 1 is that in S2, no nano-calcium phosphate loaded with high-valence iron salt is added. Other operation steps and process parameters are exactly the same as in Example 1.

[0110] Comparative Example 3

[0111] This comparative example provides a preparation process for cassava residue liquid feed based on microbial fermentation. The difference from Example 1 is that in step S1, ordinary hydroxyapatite is used instead of hydroxyapatite doped with metal ions. Other operation steps and process parameters are exactly the same as in Example 1.

[0112] Comparative Example 4

[0113] This comparative example provides a preparation process for cassava residue liquid feed based on microbial fermentation. The difference from Example 1 is that in S2, the pH of the first fermentation liquid is directly and quickly adjusted to the target pH. Other operating steps and process parameters are exactly the same as in Example 1.

[0114] Comparative Example 5

[0115] This comparative example provides a preparation process for cassava residue liquid feed based on microbial fermentation. The difference from Example 1 is that the addition of calcium carbonate is omitted in S1, while the other operation steps and process parameters are exactly the same as in Example 1.

[0116] The performance of the cassava residue liquid feed based on microbial fermentation in Examples 1-4 and Comparative Examples 1-5 was tested, and the specific process is as follows:

[0117] The concentration of metal ions in the fermentation broth was detected using atomic absorption spectroscopy.

[0118] The concentration of cyanide ions was calculated by measuring their absorbance using a spectrophotometer, taking advantage of the property that cyanide ions react with chloramine-T to form chlorocyanide, which then reacts with pyridine and barbituric acid to form a blue-violet compound.

[0119] Lactic acid content was determined using high performance liquid chromatography.

[0120] The test results are shown in Table 1.

[0121] Table 1: Performance test results of cassava residue liquid feed based on microbial fermentation in Examples 1-4 and Comparative Examples 1-5

[0122] <![CDATA[Metal ion concentration (Fe 3+ ) mg / L]]> Cyanide ion concentration (mg / L) Lactic acid content (g / L) Example 1 0.12 30.54 34.7 Example 2 0.13 30.55 34.4 Example 3 0.15 30.53 34.2 Example 4 0.14 30.56 34.5 Comparative Example 1 0.45 35.2 28.5 Comparative Example 2 0.28 52.6 30.1 Comparative Example 3 0.27 32.8 30.2 Comparative Example 4 0.13 35.3 26.8 Comparative Example 5 0.20 31.2 28.7

[0123] The test results from Example 1 and Comparative Example 1 show that hydroxyapatite doped with metal ions possesses ion exchange and complexation properties, enabling dynamic regulation of the concentration of free metal ions in the fermentation broth and preventing their inhibitory effect on microbial metabolism. Conversely, the absence of this material leads to an increase in metal ion concentration, which inhibits the metabolism of lactic acid bacteria. Furthermore, excessively high metal ion concentrations may form toxic complexes with phosphate and sulfides in the fermentation broth, further reducing fermentation efficiency; the decrease in lactic acid content is due to the inhibition of lactic acid bacteria metabolic activity at high metal ion concentrations; the effect of cyanide ion concentration is relatively small.

[0124] The test results from Example 1 and Comparative Example 2 show that nano-calcium phosphate loaded with high-valence iron salt is the core material for removing anti-nutrients. Without the addition of this material, the removal efficiency of cyanide ions is significantly reduced, and the residual concentration increases dramatically. Excessive cyanide ion concentration not only directly affects the safety of the fermentation broth but may also inhibit the metabolic activity of lactic acid bacteria, leading to a slight decrease in lactic acid production. The concentration of metal ions increases slightly because nano-calcium phosphate also has a certain degree of metal ion adsorption capacity; its absence may lead to the accumulation of more metal ions.

[0125] The test results from Example 1 and Comparative Example 3 show that ordinary hydroxyapatite lacks doping design, resulting in weak ion exchange capacity and metal ion immobilization ability. Therefore, it cannot effectively capture and regulate excess metal ions like doped hydroxyapatite. Increased metal ion concentration leads to an increase in free metal ion concentration, which has a certain toxic effect on microbial metabolism. The weaker performance of ordinary hydroxyapatite indirectly affects the efficiency of cyanide ion oxidation reaction, causing a slight increase in residual cyanide concentration. The inhibitory effect of metal ion toxicity on lactic acid bacteria metabolism leads to a decrease in lactic acid production.

[0126] The test results from Example 1 and Comparative Example 4 show that rapid pH adjustment leads to drastic changes in the fermentation broth environment. Microorganisms do not have sufficient time to adapt to this abrupt pH change, easily causing metabolic stress, inhibiting the metabolic activity of lactic acid bacteria, and significantly reducing the accumulation of lactic acid. The removal efficiency of cyanide ions depends on the oxidation reaction of ferrate, which requires a suitable alkaline environment and stable reaction conditions. Rapid pH adjustment may lead to incomplete oxidation reaction and an increase in the residual concentration of cyanide ions.

[0127] The test results from Example 1 and Comparative Example 5 show that calcium carbonate acts as a buffer during fermentation, neutralizing the organic acids produced in the fermentation broth, maintaining a suitable pH range, and providing calcium ion nutrition. If calcium carbonate is omitted, the pH of the fermentation broth easily drops rapidly to the acidic region, inhibiting the metabolic activity of lactic acid bacteria and leading to a decrease in lactic acid production. An uncontrolled acidic environment may also affect the metal ion dissolution balance, leading to Fe... 3+The concentration increases; the concentration of cyanide ions is less affected, but the residual concentration increases slightly because the oxidation reaction efficiency may be indirectly affected by the acidic environment.

[0128] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A process for preparing cassava residue liquid feed based on microbial fermentation, characterized in that, The preparation process includes: S1: Crush and sieve the cassava residue, mix it with ammonium chloride and water, adjust the pH to obtain the pre-fermentation liquid, add calcium carbonate and inoculate microorganisms to obtain the fermentation liquid, carry out the first fermentation liquid under constant temperature, and add hydroxyapatite doped with metal ions during the second stirring during fermentation. S2: Adjust the pH of the first fermentation broth to obtain the second fermentation broth. Add nano-calcium phosphate loaded with high-valent iron salts to the second fermentation broth in batches and continue stirring to obtain the third fermentation broth. Adjust the pH of the third fermentation broth to obtain the fourth fermentation broth. Continue fermentation and centrifuge to obtain cassava residue liquid feed based on microbial fermentation.

2. The preparation process of cassava residue liquid feed based on microbial fermentation according to claim 1, characterized in that, In S1: The mass ratio of cassava residue to ammonium chloride is 100:3-5; The solid content in the pre-fermentation broth is 30-35%; The amount of calcium carbonate fed is 2-5 g / L.

3. The preparation process of cassava residue liquid feed based on microbial fermentation according to claim 1, characterized in that, In S1: The initial fermentation time of the fermentation broth is 24-30 hours; The amount of hydroxyapatite doped with metal ions added is 0.3-0.5% of the mass of the fermentation broth.

4. The preparation process of cassava residue liquid feed based on microbial fermentation according to claim 1, characterized in that, In S1, the method for preparing the hydroxyapatite doped with metal ions is as follows: Calcium nitrate, ferric nitrate, and magnesium chloride were dispersed in deionized water to obtain a mixed metal salt solution; diammonium hydrogen phosphate was dispersed in deionized water to obtain a phosphate solution, which was then added dropwise to the mixed metal salt solution to obtain a mixed solution. The pH was adjusted to obtain reaction solution A. The mixture was reacted at a constant temperature, stirred, aged, filtered, washed, dried, and sieved to obtain hydroxyapatite doped with metal ions.

5. The preparation process of cassava residue liquid feed based on microbial fermentation according to claim 4, characterized in that: The molar ratio of calcium nitrate, ferric nitrate, and magnesium chloride in the mixed metal salt solution is (0.5-0.6):(0.025-0.03):(0.025-0.03). The concentration of calcium nitrate in the mixed metal salt solution is 0.8-1.2 M; The molar ratio of calcium nitrate to diammonium hydrogen phosphate is (0.5-0.6):(0.3-0.4). The temperature of the isothermal reaction in reaction solution A is 140-160℃; The reaction solution A is kept at a constant temperature for 2-3 hours.

6. The preparation process of cassava residue liquid feed based on microbial fermentation according to claim 1, characterized in that: In S2: The pH of the first fermentation broth was adjusted to 8.5-9; The pH of the first fermentation broth was adjusted using a 2% sodium bicarbonate solution, with an adjustment of 0.2 units every 1 hour for the first two adjustments, and 0.3 units every 3 hours thereafter. The amount of nano-calcium phosphate loaded with high-valence iron salt is 0.1-0.2% of the mass of the first fermentation broth.

7. The preparation process of cassava residue liquid feed based on microbial fermentation according to claim 1, characterized in that, In S2: The pH of the third fermentation broth was adjusted to 6.5-7 to obtain the fourth fermentation broth; The fourth fermentation broth continued to ferment for 1-2 days.

8. The preparation process of cassava residue liquid feed based on microbial fermentation according to claim 1, characterized in that, In S2, the preparation method of the nano-calcium phosphate supported on high-valent iron salt is as follows: Calcium nitrate solution and trisodium phosphate solution were prepared separately and mixed at a constant temperature. The pH was adjusted with ammonia water to obtain reaction solution B. The mixture was stirred and aged, centrifuged, washed, and dried to obtain the precursor. The precursor was calcined and ball-milled to obtain nano-calcium phosphate. The nano-calcium phosphate was dispersed in deionized water and ferric nitrate solution was added to obtain reaction solution C. The mixture was stirred and allowed to stand to obtain reaction solution D. The pH was adjusted and sodium hypochlorite solution was added to obtain reaction solution E. The mixture was stirred at a constant temperature, filtered, and dried to obtain nano-calcium phosphate loaded with high-valence iron salt.

9. The preparation process of cassava residue liquid feed based on microbial fermentation according to claim 8, characterized in that: The molar ratio of calcium nitrate to trisodium phosphate is 1.2-1.4:1; The precursor is calcined at a temperature of 775-785℃; The precursor is calcined for 4-5 hours. The particle size of the nano-calcium phosphate is 100-200 nm.

10. The preparation process of cassava residue liquid feed based on microbial fermentation according to claim 8, characterized in that: The mass ratio of the nano-calcium phosphate to deionized water is (40-50):200; The mass ratio of ferric nitrate to nano-calcium phosphate in the reaction solution C is 3-4:100; After adjusting the pH of the reaction solution D, a sodium hypochlorite solution with a mass fraction of 10-15 wt.% is added. The molar ratio of sodium hypochlorite to ferric nitrate is (4.5-5):2.