Technical scheme of producing amino acid fertilizer from protein waste

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Release:2022-07-20 09:28:36

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The hydrolysis of protein waste to produce amino acid fertilizer mainly includes three steps: pretreatment of raw materials, protein hydrolysis and preparation of amino acid fertilizer.
(1) Raw materials and pretreatment
Source of raw materials: Waste rich in amino acids produced by refining amino acids; Animal and plant residues rich in protein, such as leather, hair, hoof armor, blood, cotton meal, soybean cake, etc. Some raw materials need to be cleaned.
(2) Proteolysis
There have been a lot of studies on the preparation of amino acids by protein hydrolysis. The main methods of protein hydrolysis include acid hydrolysis, alkali hydrolysis and enzyme hydrolysis.
Acid hydrolysis is the main method used in the production of amino acids at present. The commonly used acids are hydrochloric acid and sulfuric acid, while phosphoric acid and nitric acid are rarely used for hydrolysis. The auxiliary means used in the acid hydrolysis process include ultrasound, microwave, etc., which are common in the experimental research stage. Qin Weijia [2] optimized the extraction of silkworm chrysalis protein and the preparation process of compound amino acids of silkworm chrysalis protein. Hydrolyze the remaining protein in the pupa meal with hydrochloric acid (the protein content is 64.4%), and the degree of protein hydrolysis can be as high as 60.4% under the condition of * * * * * *. Li Baozhu et al. [3] Hydrolyzed Soybean Meal with sulfuric acid, and the yield of * * * * * * ammonia nitrogen reached 59.9mg/g.
The amino acid hydrolysate prepared by acid hydrolysis often contains a large amount of acid. There are two main methods to remove acid - neutralization method and evaporation method. Neutralization method is to remove the acid in the hydrolysate through acid-base neutralization and generate a certain salt at the same time. The substances commonly used to neutralize the acid include alkali metal salts such as sodium hydroxide, potassium hydroxide and calcium hydroxide, gas ammonia, ammonia water and ammonium salt. The specific neutralization substance depends on the target product and economic cost. This method is applicable to all acidolysis solutions. Reduced pressure evaporation method: the acid is removed and recycled through reduced pressure evaporation. This method is applicable to the preparation of amino acids by hydrolyzing protein with hydrochloric acid, but the corresponding energy consumption will be generated, and the effect of acid removal is not ideal. At present, it is only seen in experimental research. Commercial amino acids are usually prepared by ammonium neutralization and spray drying.
The alkali used for alkaline hydrolysis is mainly sodium hydroxide and potassium hydroxide. In the alkaline hydrolysis process, most amino acids will be destroyed to varying degrees and racemization will occur, and the hydrolysis rate is usually lower than that of acid hydrolysis. Amino acid hydrolysate prepared by alkaline hydrolysis usually contains a large number of bases, which need to be neutralized, and can be neutralized with acid or protein acid hydrolysate. Li Hao and others hydrolyzed pig blood with sodium hydroxide. Under the conditions of * * * * * * hydrolysis process, 38.25mg compound amino acids can be obtained per gram of pig blood powder.
Enzymatic hydrolysis does not produce racemization, nor does it destroy protein. However, an enzyme often cannot completely hydrolyze protein, and it often requires the synergistic action of several enzymes to completely hydrolyze protein. Enzymatic hydrolysis can be directly hydrolyzed with enzymes, or with the help of microbial fermentation technology, protein can be hydrolyzed into amino acids by protease produced by microorganisms. The conditions of enzymatic hydrolysis are relatively harsh, and the current microbial fermentation technology is not mature enough to be used in the large-scale production of protein hydrolysis to prepare amino acids. Because enzymatic hydrolysis does not need neutralization procedures, and the salt produced by neutralization will not be introduced into fertilizers, it is not necessary to consider the adverse impact of salt accumulation caused by continuous farming on the land. Based on the perspective of environmental protection, With the progress of microbial fermentation technology, the preparation of amino acids by enzymatic hydrolysis, especially microbial fermentation, is still quite advantageous. Li tingxun et al. [5] used Bacillus licheniformis and protease to degrade livestock blood into liquid amino acids. Zhang Wenfeng [6] used excess sludge as raw material to prepare sludge protein extract by enzymatic hydrolysis, and then hydrolyzed the sludge protein extract obtained under the conditions of ******* enzymatic hydrolysis to prepare composite amino acids. Under the conditions of ****** hydrolysis with pH10.0, enzyme dosage of 9mg/ml, 8h, 55 ℃, 10.62g composite amino acids can be obtained per 100g of dry sewage sludge.
(3) Preparation of amino acid fertilizer
The treated amino acid hydrolysate can be directly prepared into solid amino acid powder after concentration and drying. The powder can be directly sprayed on crops in the form of nutrition, or added to fertilizers in the form of nutrients, so as to prepare amino acid ecological fertilizer, amino acid compound fertilizer, amino acid water-soluble fertilizer, amino acid leaf fertilizer and other amino acid fertilizers; Using the complexing property of amino acids, medium and trace elements can also be added to amino acid hydrolysate to prepare amino acid chelated micro fertilizer. Xulijuan et al. [7] prepared complex amino acid trace element chelate Hefei from composite amino acid and trace elements manganese, zinc and copper hydrolyzed from animal protein waste. Li tingxun of Qingdao Shujun fertilizer Co., Ltd. [5] used Bacillus licheniformis and protease from soybeans to degrade livestock blood into liquid amino acids, and used this liquid amino acids to prepare amino acid liquid fertilizer.

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