Effects Of Protein Degradation Bacteria Fermentation Of Soybean Meal On Coho Salmon

This paper aims to investigate the effects of protein degrading bacteria fermenting soybean meal on the growth,antioxidant,immune,protein metabolism related enzymes,and gene expression of coho salmon.Two strains with high protease production were obtained by screening bacteria,and the optimal fermentation conditions were determined to ferment soybean meal.Coho salmon with similar weight were randomly divided into four kinds of iso-nitrogen and iso-lipid diets.Soybean meal and fermented soybean meal were used to replace 10% protein content of fish meal,respectively.The G0 diet(control group)contained 40.07% fish meal,and 14.08% fish meal(10% crude protein)of the other diets was replaced by unfermented or fermented soybean meal.The G1 diet contained 21.20%unfermented soybean meal(10% crude protein),and the G2 diet contained17.87% Enterococcus lactis S7 fermented soybean meal(10% crude protein).The G3 diet contained 17.18% fermented soybean meal(10%crude protein)of Bacillus pumilus L.Juvenile coho salmon were fed for 10 weeks.The results are as follows:1.Two strains of macromolecular protein degrading bacteria were screened from mangrove soil.The strains were identified as Bacillus pumilus and Enterococcus lactis by 16 S r DNA sequencing and physiological and biochemical identification.Through single factor optimization and orthogonal optimization,the optimal fermentation conditions were determined as follows: inoculating 6% Bacillus pumilus L39 ℃ for 36 h and inoculating 8% Enterococcus lactis S737 ℃ for 36 h with glucose as carbon source material-water ratio 1: 1.Compared with unfermented soybean meal,the crude protein content and acid-soluble protein content of the two fermented soybean meal were significant(P<0.05);The contents of β-conglobulin,soy globulin,urease and trypsin inhibitor were significant(P<0.05).2.Compared with the control group(G0),the growth performance and antioxidant capacity of G1 group were significant(P<0.05).The antioxidant capacity of G2 and G3 groups was significant(P<0.05).Compared with the control group(G0),the specific growth rate and weight gain rate of G3 group were significant(P<0.05),and other growth indexes were not significantly different(P>0.05).There was no significant difference in growth performance between G2 group and control group(P>0.05).The results showed that the two kinds of fermented soybean meal instead of fish meal had no adverse effects on the growth performance of coho salmon,and could optimize the serum biochemical indexes of coho salmon and significantly improve the antioxidant capacity of coho salmon.Among them,soybean meal fermented by Bacillus pumilus L instead of fish meal can promote the growth of salmon to some extent,and soybean meal fermented by Enterococcus lactis S7 instead of fish meal can significantly improve the antioxidant capacity of salmon.3.Compared with the control group(G0),the digestive enzyme activity,immunity and the expression of mTOR pathway related genes in G1 group were significant(P<0.05);The activity of digestive enzymes and the expression of genes related to mTOR pathway in G2 and G3 groups were significant(P<0.05).The results showed that the two kinds of fermented soybean meal instead of fish meal could significantly improve the digestive enzyme activity and immunity of salmon and the expression of mTOR pathway related genes.Soybean meal fermented by Bacillus pumilus L instead of fish meal promoted the activity of digestive enzymes and the expression of genes related to mTOR pathway more significantly.Enterococcus lactis S7 instead of 10% fish meal enhanced the immunity of salmon more significantly.In this study,two strains degrading macromolecular proteins were screened and identified to produce fermented soybean meal after optimizing fermentation conditions.It was found that the two kinds of fermented soybean meal had no adverse effects on the growth of salmon,and could significantly improve the antioxidant capacity,the activity of immune digestive enzymes and the expression of mTOR pathway related genes of salmon.The results of this study provide basic data for replacing fish meal with fermented soybean meal and provide basis for developing new protein sources.