Technical scheme for producing amino acid fertilizer from protein waste

　　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

　　Raw material source: Waste rich in amino acid components produced by refining amino acids; Animal and plant wastes rich in protein, such as leather, hair, hoof armor, blood, cotton meal, soybean cake, etc. Some raw materials need to be cleaned.

　　(2) Protein hydrolysis

　　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 amino acid production at present. The commonly used acids are hydrochloric acid and sulfuric acid, and few are hydrolyzed with phosphoric acid and nitric acid. The auxiliary means used in the acidolysis process include ultrasound, microwave and so on, which are common in the experimental research stage. Qin Weijia [2] optimized the extraction of silkworm pupa protein and the preparation process of silkworm pupa protein composite amino acids. The residual protein in pupa meal was hydrolyzed with hydrochloric acid (the protein content was 64.4%). 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 from 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 and ammonium salts. The specific neutralization substance depends on the target product and economic cost. The method is applicable to all acidolysis solutions. Vacuum evaporation method: the acid is removed and recycled by vacuum evaporation. This method is applicable to the preparation of amino acids by hydrolyzing protein with hydrochloric acid, but it will produce certain energy consumption, and the effect of acid removal is not ideal. At present, it is only seen in experimental research. Commercial amino acids are prepared by ammonium neutralization and spray drying.

　　The alkali used in alkali hydrolysis is mainly sodium hydroxide and potassium hydroxide. In the process of alkali hydrolysis, most amino acids will be destroyed in varying degrees and racemization will occur, and the hydrolysis rate is usually lower than that of acid hydrolysis. The amino acid hydrolysate prepared by alkaline hydrolysis usually contains a large amount of alkali, which needs 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 condition of ******** hydrolysis process, 38.25mg composite amino acids can be obtained per gram of pig blood powder.

　　Enzymatic hydrolysis does not produce racemization and does not destroy protein. However, one enzyme can not completely hydrolyze the protein, and it often needs the cooperation of several enzymes to completely hydrolyze the protein. Enzymatic hydrolysis can be directly hydrolyzed with enzymes, or proteins can be hydrolyzed into amino acids by using protease produced by microorganisms with the help of microbial fermentation technology. The conditions of enzymatic hydrolysis are relatively harsh, and the current microbial fermentation technology is not mature enough to be applied to the large-scale production of protein hydrolysis to prepare amino acids. Because enzymatic hydrolysis does not need neutralization procedure and does not introduce the salt produced by neutralization into fertilizer, it is not necessary to consider the adverse impact of salt accumulation caused by continuous farming on the land, From 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] degraded livestock blood with Bacillus licheniformis and protease to make liquid amino acids. Zhang Wenfeng [6] prepared sludge protein extract by enzymatic hydrolysis with surplus sludge as raw material, and then hydrolyzed the sludge protein extract obtained under the condition of ****** enzymatic hydrolysis to prepare composite amino acids at pH 10 0. Under the conditions of ***** hydrolysis with enzyme dosage of 9mg / ml, 8h and 55 ℃, 10.62g compound amino acids can be obtained per 100g dry sludge.

　　(3) Preparation of amino acid fertilizer

　　The treated amino acid hydrolysate can be directly prepared into solid amino acid powder through concentration and drying treatment. The powder can be directly sprayed on crops in the form of nutrition or added into fertilizer in the form of nutrition, so as to prepare amino acid ecological fertilizer, amino acid compound fertilizer, amino acid water-soluble fertilizer, amino acid foliar fertilizer and other amino acid fertilizers; Amino acid chelating micro fertilizer can also be prepared by adding medium and trace elements into amino acid hydrolysate. Xu Lijuan et al. [7] prepared complex amino acid trace element chelators with complex amino acids and trace elements manganese, zinc and copper hydrolyzed from animal protein waste as raw materials. Li tingxun of Qingdao Shujun fertilizer Co., Ltd. [5] used Bacillus licheniformis and protease from soybean to degrade livestock blood to make liquid amino acids, and used the liquid amino acids to prepare amino acid liquid fertilizer.