Preparation Of Feeding Peptides By Soybean Meal Co-processing With Microbes And Protease

Soybean meal, a by-product after oil extraction, crude protein content of 43-48%, high content of essential amino acids, is the most widely used source of dietary protein in the poultry and swine industry. Small peptide is compounds of 2 or more amino acids linked by peptide bonds, it's molecular weight between 1-2 kD. In this study, microbiological methods and enzymatically methods was used to treated soybean meal, to increase the content of peptides. The study is of great practical significance to make up of high-quality protein feed, especially the shortage of protein resources, to reduce farming cost of production, to promote livestock output.One strain of Bacillus subtilis BSW-2 was screened to degrade protein macromolecules of soybean meal into small peptides from 8 strains preserved by our laboratory. After fermented, the content of peptide increased from 13.35 mg/g to 108.10 mg/g. One strain of yeast YT was also screened to improve the content of crude protein. After fermented, the crude protein content increased from 47.62% to 55.32%.The process condition of soybean meal fermentation by BSW-2 and YT was established. The results showed that the optimum fermentation parameters were mixed inoculation volume 1.5%, ratio of material to water 1:1.0, fermentation temperature 30℃, fermentation time 36 h. After fermentation, the content of peptides increased from 13.35 mg/g to 184.57 mg/g. The crude protein content increased from 47.62% to 56.38%. The vitro digestibility of protein increased from 81.86% to 91.99%. The dry matter digestibility vitro increased from 66.00% to 71.40%. The content of lactic was 2.65%. The urease activity decreased from 0.45 U to 0.15 U. The results of SDS-PAGE shows that the protein macromolecular and the antigen protein was degraded.The neutral protease was screened and the condition of enzymatic hydrolysis was established. The results showed that the optimum condition were neutral protease 400 u/g, ratio of material to water 1:1.6, reaction temperature 50℃, hydrolysis time 48 h. Under that condition, the content of peptides increased from 13.35 mg/g to 185.72 mg/g. The crude protein content increased from 47.62% to 52.59%. The results of SDS-PAGE shows that the protein macromolecular and the antigen protein was also degraded.An orthogonal test experiment was conducted to investigate the optimal conditions of soybean meal fermentation by Bacillus subtilis BSW-2, Saccharomyces cerevisiae YT and a neutral protease for improving the content of peptides. The results showed that the optimum conditions were mixture inoculum 1.5%, neutral protease 450 u/g, ratio of material to water 1:1.4, fermentation temperature 40℃, fermentation time 48 h. Under that condition, all the indicators were better than fermentation only and neutral protease only. The content of peptide increased from 13.35 mg/g to 199.65 mg/g. The crude protein content increased from 47.62% to 56.72%. The vitro digestibility of protein increased from 81.86% to 92.79%. The vitro dry matter digestibility increased from 66.00% to 72.30%. The content of lactic acid was 2.75%. The urease activity decreased from 0.45 U to 0.086 U. The results of SDS-PAGE shows that the protein macromolecular and the antigen protein was almost degraded.PCR-DGGE method was used to analysis the change of bacterial communities in the collaborative process, the results show that BSW-2 was in a dominant position throughout the fermentation process. With the fermentation time, BSW-2 can inhibit the growth of other bacteria, so it can have an absolute advantage.