Solid-state fermentation of pearl millet with Aspergillus oryzae and Rhizopus azygosporus: effects on bioactive profile and DNA damage protection activity

Abstract

The present scientific work envisaged the effect of fermentation, starter culture, solvent type, concentration of solvent and extraction conditions on pearl millet phenolics. Fermentation of pearl millet grains was performed using two filamentous fungal strains (Aspergillus oryzae and Rhizopus azygosporus) for a specific period (336 h). Pearl millet koji was extracted under optimized conditions and studied for the presence of specific bioactive compounds using high performance liquid chromatography (HPLC). Results confirmed the presence of ascorbic acid (1.55 mg g−1), p-coumaric acid (1.04 mg g−1) and cinnamic acid (0.71 mg g−1 as major compounds in unfermented pearl millet and ascorbic acid (10.23 mg g−1), gallic acid (8.95 mg g−1), resorcinol (2.90 mg g−1, catechol (7.60 mg g−1), vanillin (4.58 mg g−1), p-coumaric acid (3.96 mg g−1), quercetin (2.74 mg g−1), benzoic acid (5.10 mg g−1) and cinnamic acid (5.14 mg g−1) in A. oryzae fermented millet (AoFM). Specific phenolics in R. azygosporus fermented millet (RaFM) were ascorbic acid (8.80 mg g−1), gallic acid (4.70 mg g−1) and p-coumaric acid (1.27 mg g−1) along with other minor phenolics. DNA damage protection activity was observed maximum till 288 h of fermentation for AoFM and 240 h of fermentation for RaFM.