Characterization and fermentation of Bamboo leaf litter biomass for ethanol production

Abstract

Bamboo leaf litter (BLL) biomass was washed to remove adhering debris, dried and powdered (0.5 mm) to investigate its physico-chemical properties. BLL biomass was found to contain (4.3%) moisture, (5.5%) ash, (81.5%) volatile matter, (36%) carbon, (5.3%) hydrogen and (2.1%) nitrogen with calorific value of 15.42 MJ/kg. Pre-treatment approaches such as fungal solvolysis; fungus alkaline extraction; dilute acid-alkali and microwave-alkali-acid pre-treatment were executed to obtain maximum reducing sugar yield for ethanol production. Microwave-alkali-acid was found to be best pre-treatment strategy with 76% increase in cellulose content while decrease in hemicellulose and lignin was observed to be 34% and 54% respectively. Reducing sugar yield was enhanced from 30 mg/g to 193.7 mg/g along with saccharification efficiency of 25.8% for microwave-alkali-acid pre-treatment. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared analysis (FTIR), Solid state 13C CP/MAS NMR spectroscopy, Thermal gravimetric analysis (TGA) on native and microwave-alkali-acid pre-treated biomass was done to investigate physical and chemical changes. Further, microwave-alkali-acid pre-treated BLL biomass was used as substrate for ethanol production using partially purified cellulase from Bacillus subtilis NA15 followed by ethanol fermentation using Saccharomyces cerevisiae (NCIM 3215) via SSF. The statistical optimization of ethanol production using Taguchi orthogonal array design produced 12.84 g/L of ethanol with optimized parameters of 11% substrate loading, 0.5% enzyme loading, 8% yeast inoculum at 4.5 pH and 30°C temperature after 72 h of fermentation. The optimized process parameters may be used for production of ethanol using BLL biomass at pilot scale.