Abstract: The effects of high-yielding protease yeast on the quality of fermented soybean meal under different conditions were studied in this study.The fermentation time,water content,inoculation amount of bacteria solution and glucose addition were optimized by using protease protease activity as the index.Orthogonal test was designed based on the single factor test results to explore the changes of fermentation on the activities of protease,cellulase,phytase,pectinase and the contenets of crude protein,small molecule polypeptide and pancreatic protein inhibitor in soybean meal.The results showed that the enzymatic activity of soybean meal was the highest when the water content was 50%,the added amount of bacterial liquid was 4% and the glucose addition was 1.5%.Based on these results,orthogonal experiments were designed and found that compared with the control group,all experimental groups exhibited increased protease activity by 100.56%-380.13%,cellulase activity by 2.67%-81.77%,phytase activity by 53.89%-252.81%,pectinase activity by 13.84%-70.83%,small-molecule polypeptide contents by 574.67%-1 981.08%,crude protein contents by 9.24%-16.49%,pancreatic protein inhibitor contents by 7.36%-67.39%.The fermentation of soybean meal by high-protease yeast could significantly improve its nutritional value and reduce its anti-nutritional factors.Soybean meal was fermented by high yield protease yeast.If the soybean meal had the highest hydrolase activity,the fermentation conditions were 1% glucose,2% mixed bacterial fluid and 45% water content fermentation at room temperature for 5 days.When the contents of crude protein,polypeptide,and the contents of trypsin inhibitor detoxification rate were highest,the fermentation conditions were 2% glucose,4% mixed bacterial solution,55% water content and fermentation for 5 days at room temperature.

Key words: yeast; protease; hydrolytic enzymes; crude protein; anti-nutritional factors