Studies on the performance of a new bioreactor for improving antioxidant potential of rice

In the present investigation, we studied the performance of a self-designed new bioreactor (NB) for the improvement of phenolics and antioxidant activity in rice koji and the results were compared with the conventional solid-state fermentation (SSF). The non-fermented (control) and fermented masses obtained from two fermenters were extracted with water, methanol and ethyl acetate. Interestingly, rice fermented in NB resulted in a higher yield of phenolics and DPPH (1-1 Diphenyl-2-picryl hydrazyl) scavenging activity in each of the extraction media as compared to SSF and control. This might be due to the higher titre values of β-glucosidase (62.7%) and α-amylase (40.7%) in the extraction media of NB compared to SSF. It was verified by in vitro assay for phenolic enrichment in presence of α-amylase and β-glucosidase using rice as the substrate. An interesting finding was that though polyphenol content was maximum in ethyl acetate fraction, fractions extracted with water showed the highest antioxidant activity under all fermentation conditions, presumably because of the different phenolic composition which was substantiated by studying the antioxidant values of the extracts with same phenolic content in the antioxidant assay system.