Effects of Lactic Acid Bacteria Fermentation on the Content of Sugars and Polyphenols of Defatted Rice Bran
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Abstract:
This study investigated the influence of fermentation by different lactic acid bacteria on the sugar and polyphenol content of defatted rice bran. Semi-dry enzymatic hydrolysis was used to increase the fermentable sugar content in defatted rice bran. After being treated with semi-dry enzymatic hydrolysis and sterilization, the defatted rice brans were inoculated with Lactobacillus bulgaricus, Streptococcus lactis, L. plantarum, L. casei, and Leuconostoc mesenteroides, respectively. Changes in the viable count of lactic acid bacteria, and the content of total sugar, reducing sugar, soluble polyphenols, and insoluble polyphenols during the fermentation were studied. The results showed that semi-dry enzymatic hydrolysis increased the content of reducing sugar in defatted rice bran to 155.08 mg/g, almost six times higher than that of the untreated defatted rice bran. All five lactobacilli grew in the defatted rice bran, but significant differences were found among their growth rates after entering the logarithmic phase. Among the five lactobacilli, L. acidophilus exhibited the strongest sugar transformation capacity; after 72-hour fermentation by L. acidophilus, the content of total sugar and reduced sugar decreased by 31.33% and 60.76%, respectively. The highest content of soluble polyphenols (33% increase) was observed after 24-hour fermentation by L. acidophilus; after 72-hour fermentation, the insoluble polyphenol content decreased by 20.32%, significantly better than those of other four stains.
