Bacillus subtilis Fermentation for Enhancement of Feed Nutritive Value of Soybean Meal

In order to increase the nutritional quality of soybean meal (SBM) as an animal feed, Bacillus subtilis TP6, a previously isolated strain from an Indonesian traditional fermented soybean food, Tempeh, was used as a starter organism for solid-state fermentation. In the pre-treated SBM with water content of 60% (v/w), B. subtilis TP6 was grown to a maximum viable cell number of $3.5{\times}10^9CFU/g$. Compared to control, crude protein in Bacillus fermented SBM was increased by 16%, while raffinose, stachyose, and trypsin inhibitors were reduced by 31, 37, and 90%, respectively. The Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed that proteins in the fermented SBM were remarkably hydrolyzed into smaller molecular masses, resulting in a decrease in large sized proteins. Our data suggested that B. subtilis fermentation could increase the nutritive value of SBM through reduction of anti-nutritive factors and improvement of protein quality by hydrolysis of soy protein. In addition, B. subtilis TP6 produced a functional ingredient, poly-${\gamma}$-glutamic acid which has various health benefits.