Effect of fermentation by Bacillus subtilis on antioxidant and cytotoxic activities of black rice bran

Summary Black rice bran was fermented with B acillus subtilis KU 3 isolated from K orean traditional food, K imchi. Antioxidant and cytotoxic activities of the fermented black rice bran were investigated. Total phenolic and anthocyanin contents decreased from 171.54 mg GAE g −1 and 2.31 mg g −1 to 139.13 mg GAE g −1 and 2.12 mg g −1 , respectively, after fermentation. Antioxidant activities determined by 1,1‐diphenyl‐2‐picrylhydrazyl ( DPPH ) radical scavenging, β‐carotene bleaching and ferric thiocyanate assay were correlated with total phenolic and anthocyanin contents. Non‐fermented black rice bran extract ( NFBE ) showed greater antioxidant activities than fermented black rice bran extract ( FBE ). Cytotoxic activities measured by MTT assay showed that both NFBE and FBE had over 50% activities. The cytotoxic activities of FBE against MCF ‐7 and H e L a cells were 71.65% and 68.07%, respectively, at 8.0 mg mL −1 , but those of NFBE were lower than 50%. These results suggested that the cytotoxic activity of black rice bran improved through fermentation, while antioxidant activity reduced.