Optimization of saccharification conditions of black rice (cv. Poireton) using microbial strains through response surface methodology

Black rice of Manipur (India) is almost six times richer in antioxidant activities as compared with other rice varieties, is gluten free, gut friendly and a natural cleaner with many medicinal values, and cultivar ‘Poireton’ occupies almost all premium markets worldwide. A statistical model was developed to describe the saccharification process by using established microorganisms viz., Aspergillus oryzae ATCC10124 and Bacillus subtilis ATCC11774m in black rice (cv. Poireton) . Saccharification parameters were optimized by response surface methodology with a three‐level, three‐variable Box–Behnken design. The optimized combinations of pH, temperature and time were obtained for the maximum reducing sugars, total phenol content in terms of gallic acid equivalent, free amino nitrogen and acidity. The optimized values obtained by response surface methodology with all of the factors included pH 7.37, incubation period 63.9 h and temperature 43.1°C. The values of responses, viz. reducing sugars, total phenol content, free amino nitrogen and acidity, were: 3.22 mg/mL, 435.7 μg/mL, 3.85 mg/mL and 0.15%; and 3.27 mg/mL, 438.5 μg/mL, 3.75 mg/mL and 0.18% for predicted and experimental, respectively, and correlated closely. This statistical approach for obtaining the optimal conditions of saccharification process (taking fermentable sugar as substrate) was further used for ethanol production. Copyright © 2017 The Institute of Brewing & Distilling