Abstract: In order to screen an excellent strain which can utilize soybean meal to produce proteases under anaerobic conditions, 10 pure strains conserved in our laboratory were compared for their abilities to produce proteases and degrade crude proteins in solid-state fermenting soybean meal as well as colonial features. NCU646 was found to be the best strain. The protease activity at the end of solid-state fermentation of soybean meal by this strain reached up to 9600 U/g, and fermented soybean meal showed over 10-fold increase in the content of small peptides and nearly 10.0% increase in crude protein content in comparison with unfermented soybean meal. Physiological and biochemical identification and 16S rRNA sequence analysis revealed that NCU646 was a Bacillus subtilis strain.

Key words: soybean meal, anaerobic fermentation, conversion rate of small peptides, strain identification