Isolation of bacteria from fermented food and grass carp intestine and their efficiencies in improving nutrient value of soybean meal in solid state fermentation

Background: Soybean meal is an excellent and cost-effective protein source; however, its usage is limited in the piglet due to the presence of anti-nutritional factors and the antigens glycinin and beta-conglycinin. The objective of the current study was to screen and select for bacteria that can be efficiently adopted to ferment soybean meal in order to solve this problem. Results: Bacteria were isolated from fermented soy foods and the grass carp intestine, and strains selected for high protease, cellulase and amylase activities. The isolated bacteria were characterized as Bacillus cereus, Bacillus subtilis and Bacilus amyloliquefacien, respectively. Fermentation with food-derived Isolate-2 and fish-derived F-9 increased crude protein content by 5.32% and 8.27%, respectively; improved the amino acid profile by increasing certain essential amino acids, broke down larger soy protein to 35 kDa and under, eliminated antigenicity against glycinin and beta-conglycinin, and removed raffinose and stachyose in the soybean meal following a 24-h fermentation. Conclusions: Our results suggest these two B. amyloliquefaciens bacteria can efficiently solid state ferment soybean meal and ultimately produce a more utilizable food source for growing healthy piglets.