Shipin yu jixie (Oct 2023)
Process study on mixed bacterial solid-state fermentation of rice bran for the preparation of oryzanol and evaluation of its antioxidant activity
Abstract
Objective: In order to improve the yield of oryzanol of rice bran. Methods: Rice bran was selected as the research subject, and Saccharomyces cerevisiae and Bacillus subtilis were selected as solid-state fermentation strains through single-factor experiments. The mixed bacterial solid-state fermentation process was optimized by Box-Behnken response surface method combined with the single factor experiments, based on the content of oryzanol. The antioxidant activity of the fermentation extracts was evaluated using DPPH and ABTS free radical scavenging assays. Scanning electron microscopy （SEM） was used to analyze the principle of oryzanol enrichment in mixed bacterial solid-state fermentation. Results: Under the of mixed bacterial treatment of saccharomyces cerevisiae and Bacillus subtilis, the optimal fermentation conditions for rice bran oryzanol was determined to be a fermentation time of 44 h, a fermentation temperature of 34 ℃, an inoculum size of 10%, and a moisture content of 40%. Under these conditions, the oryzanol content was （7.816±0.038） mg/g, which was 1.9 times higher than that of unfermented rice bran. The extracts prepared by mixed bacterial solid-state fermentation exhibited strong DPPH and ABTS free radical scavenging activity, with IC50 values of （0.220±0.007）, （0.409±0.014） mg/mL, respectively. These values represented a reduction of 28.6% and 39.7% compared to unfermented rice bran. SEM observation revealed showed that that the surface of rice bran tissue had less oil, a looser and more porous structure after mixed bacterial solid-state fermentation, which was more conducive to the release of rice bran oryzanol. Conclusion: Mixed solid-state fermentation of bacteria significantly increases the oryzanol content and antioxidant activity of rice bran.
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