Role of Aspergillus flavus on Biodegradation of Lignocellulosic Waste Millet Straw and Optimization Parameters for Enzyme Hydrolysis and Ethanol Production under Solid State Fermentation

Amongst six natural lignocellulosic waste/raw material screened, millet straw contained maximum cellulose (30 %) and physical and chemical pre-treatment yielded maximum cellulase activity. The composition of millet straw showed 30 % cellulose, 10 % hemicellulose, 8.73 % total organic carbon, 0.7 % total nitrogen and 0.8 ppm phosphorous. Amongst four fungi of genus Aspergillus isolated from local soil dumps of kitchen and garden waste, Aspergillus flavus showed maximum cellulase activity on CMC agar medium and used for degradation of millet straw. Amongst five media, Mandle and Sternberg fermentation medium showed maximum enzyme activity due to favorable pH and supplementing nitrogen and mineral requirements for growth and development of Aspergillus flavus. The optimum parameters for maximum cellulolytic enzyme activity in solid state fermentation were also studied which showed that 1 ml inoculum size, 4.5 pH of the medium, incubation at 28 °C and 70 % moisture content for 120 h, 3.0 % w/v substrate concentration, 0.1% supplementation of carbon source in form of Carboxy Methyl Cellulose and 0.5 % of nitrogen source in form of ammonium sulphate found effective for better endoglucanase activity. The hydrolysate was subjected to saccharification (fermentation through yeasts Saccharomyces cerevisiae) having potential of producing 0.15 g/hour/liter of ethanol at above optimized parameters.