Effect of solid-state fermentation on amino acid profile and phytochemicals of red rice bran

We aimed to evaluate the effects of solid-state fermentation (SSF) on red rice bran, specifically for a new rice variety (RD69,Tubtim Chumphae) in Thailand. Fermentation of red rice bran with Aspergillus oryzae was continued for 6 days at 30 degrees C, and LC MS/MS was used to determine the free amino acid composition, antioxidant activity of 2,2-diphenyl-1-picrylhydrazyl, ferric reducing antioxidant power, presence of phenolic and flavonoid compounds, and cytotoxicity in HeLa cells. The results showed that SSF significantly increased (p < 0.05) the total amino acid content by 59.00% after 5 days of fermentation. Fermented red rice bran (FRRB) contained a significant increase (p < 0.05) in antioxidant activity and compounds, which reached their maximum levels by fermentation for 5 days. FRRB also exhibited increased cytotoxicity in HeLa cells compared with unfermented rice bran. The increases of cytotoxicity and antioxidant activities were due to enzymatic hydrolysis and fermentation, in correspondence with the increase in phenolic and flavonoid compounds, suggesting that enzymatic hydrolysis improves the nutritional and phytochemical properties. Notably, the duration of fermentation is a key to optimizing the biological activity of the fermented product.