Isolation of Bacillus spp. from Korean fermented foods and their application in black rice bran fermentation

An appropriate strain of Bacillus spp. derived from traditional Korean fermented foods was selected for fermentation of black rice bran, and the fermented bran’s nutritional components were analyzed. Among 18 isolated Bacillus spp. strains, the five (KU3, KU24, KU28, KU611, and KU612) that exhibited both amylolytic and proteolytic activities were selected for fermentation. Among these, Bacillus sp. KU3 showed notable dual enzymatic activity. During fermentation in black rice bran medium, Bacillus sp. KU3 increased from 5.83 to 7.83 Log CFU/mL after 24 h. The KU3 strain was identified as Bacillus subtilis using an API 50 CHB kit and 16S rRNA sequencing. Black rice bran (4% w/v) was fermented with B. subtilis KU3 at 37°C, 150 rpm for 24 h. Following fermentation, the main component of the fermented black rice bran was carbohydrate (77.13%). An increase in ash content was observed, while other nutritional components showed no significant changes. These results suggest that B. subtilis KU3 is a viable strain for black rice bran fermentation.