| With the increasingly serious global issues such as resources, environment, etc, circular economy and sustainable development has become the mainstream of development trend nowadays. Therefore, to make a research on the performance of biodegradability of the chrome leather scrap, and make the products from biodegradable material used in animal feed preparation, can not only reduce the tanning waste on the environment caused by pollution, but also can reach a reasonable and effective use of biomass resources.This research takes chrome leather scrap as raw materials, then though the comparison for different enzyme hydrolysis test, to choose neutral protease to hydrolyzed it, and analyses the amino acid composition within the hydrolysis product; to take the hydrolysis rate and chromium content as evaluation standard to investigate the influence of hydrolysis temperature, hydrolysis time, enzyme dosage and hydrolysis effects by bath pH, and to optimize the neutral protease hydrolysis conditions through orthogonal test; to dry the hydrolysate to get protein powder, then analyze the physical and chemical properties of the protein powder; to make the protein powder, corn, wheat flour, wheat bran, soybean meal, calcium hydrogen phosphate and oil mixed in proportion to obtain animal feed. Then the paper explores that how the different additives of leather protein powder influenced on the growth situation and blood sugar of mouse.The result of enzyme hydrolysis shows that in the same condition of enzyme activity unit, neutral protease shows best hydrolysis effect to dechromed shavings, the second is alkaline protease, and the acidic protease is the last one. Therefore to hydrolyze chrome leather scrap by neutral protease is feasible. The sequencing of influencing factors against the hydrolysis is: hydrolysis temperature, enzyme dosage, hydrolytic time, and hydrolytic pH value. The optimized hydrolysis conditions are as follows:hydrolytic temperature55℃, hydrolytic time4h, the amount of protease2%, hydrolytic pH=7.0. The hydrolysis rate of the chrome shavings can be increased to97.61%under such conditions, nitrogen yield are78.84%, and the chrome contents of the hydrolysate are only0.31×104g/L. This result shows that not only the neutral protease can hydrolyzed leather chrome shavings effectively, but also the products can contain lower content of chrome. Enzymatic hydrolysate contains17kinds of basic amino acid composition, including a large number of tyrosine and rich alanine, methionine and the composition such as glutamic acid, But threonine, isoleucine and arginine component relative shortage. Total amino acid hydrolysate can reach up to91.265g/LAfter drying the protein hydrolysate on physical and chemical analysis, this research gets the results which indicate that:the leather protein powder of protein content are90.8%, the total free amino acid content are49.80g/100g, and at the same time, chrome content for181ppm. Protein powder is hydrolyzed from leather chrome scrap which is added to make animal feed. Animal experiment results show that in the range of0.5%-1.5%, neither leather protein powder reduce the growth rate of mouse, nor can make the lethal effect on them, however, the lack of protein powder can affect the growth rate of mouse. By the way of blood glucose value, through the comparison experiment group which add leather protein powder to the feed with the standard group, though there is no significant difference (P≥0.05), the average blood glucose value decreased0.5,1.2and0.5mmol/L respectively. The experiment group which does not add leather protein powder almost has no influence on blood glucose value of mouse. To join the range of5%-1.5%of leather protein powder in animal feed, can achieve the results that neither affect the weight growing as normal, at the same time, reduce blood sugar. Therefore the research to use leather wastes to produce animal feed has theoretical and practical significance. |
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