Optimization of fermentation conditions for Aspergillus niger on de-oiled rice bran as a substrate

An in-vitro trial was conducted to optimize the fermentation conditions using Aspergillus niger on de-oiled rice bran (DORB) by varying the substrate with three different ratios of DORB and water i.e. 70: 30, 60: 40, and 50: 50 each for a constant incubation periods of 72 hrs, at constant temperature 37°C. The lyophilized culture of Aspergillus niger was reconstituted and subculture was made by agar plating technique using potato dextrose agar. Spore suspension was inoculated at the rate of one lac spore per kg of substrate. Thus, three different conditions were evaluated in triplicate for growth of Aspergillus niger and its effect on various chemical constituents in de-oiled rice bran (DORB) to get best suitable combination for solid substrate fermentation of DORB. As moisture level in the substrate DORB increased, the DM loss decreased gradually. Amongst all fermented groups, lowest DM loss (21.13%) was noted in fermented de-oiled rice bran soaked with water at the ratio of 50: 50 (w/v), whereas; the highest DM loss (25.41%) was observed in fermented de-oiled rice bran soaked with water at the ratio of 70: 30 (w/v). Fungal fermentation of DORB increased CP from 14.56 to 18.56%, EE from 1.13 to 1.36%, Ca from 0.30 to 0.47% and GE from 3881 to 3986 kcal/kg whereas, decreased the CF from 12.85 to 7.38%, thus enhancing the nutritional worth of DORB. Optimum conditions for better growth of Aspergilus niger and economic fermentation on DORB was found to be DORB and water ratio of 50: 50 (w/v) for incubation period of 72 h at 37°C.