混菌固态发酵米糠产谷维素的工艺及抗氧化活性评估

Process study on mixed bacterial solid-state fermentation of rice bran for the preparation of oryzanol and evaluation of its antioxidant activity

目的:提高米糠谷维素的得率。方法:以米糠为研究对象,经单因素试验筛选出酿酒酵母和枯草芽孢杆菌作为固态发酵菌种,以谷维素含量为指标,通过单因素试验结合Box-Behnken响应面法优化混菌固态发酵工艺,采用DPPH自由基和ABTS自由基清除试验对发酵提取物抗氧化活性进行评价,并通过扫描电镜(SEM)分析混菌固态发酵法富集谷维素的原理。结果:在酿酒酵母和枯草芽孢杆菌混菌处理下,米糠谷维素最优发酵工艺为发酵时间44 h,发酵温度34℃,接种量10%,含水量40%,在此条件下谷维素含量为(7.816±0.038)mg/g,是未发酵米糠谷维素含量的1.9倍。混菌固态发酵法制备的提取物具有较强的DPPH自由基和ABTS自由基清除活性,其IC50值分别为(0.220±0.007),(0.409±0.014)mg/mL,与未发酵米糠相比,其IC50值分别降低了28.6%和39.7%。SEM分析结果显示,混菌固态发酵后米糠组织表面油脂更少,结构疏松多孔,更加有利于米糠中谷维素的释放。结论:米糠经混菌固态发酵后,谷维素含量和抗氧化活性均得到显著提高。

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 IC 50 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.