Bio-ethanol and bio-butanol production from orange peel waste

Orange (Citrus sinensis) peel waste was used as the substrate for bio-fuels production. It was treated with a steam explosion process to carry out its hydrolysis, and the hydrolysate was utilized as a fermentation medium. The steam explosion method variables of acid concentration, residence time and substrate concentration were optimized. Bio-ethanol and bio-butanol were produced in this study using Saccharomyces cerevisiae NCIM 3495 and Clostridium acetobutylicum NCIM 2877, respectively. The optimized parameters for the steam explosion process were 1% v/v acid concentration, 10 min residence time and 15% w/v substrate concentration. Maximum bio-ethanol yield of 4.1 g/100 mL from orange peel hydrolysate as production media was achieved with the optimized parameters such as 24 hr inoculum incubation time, 20% v/v inoculum size and 48 hr fermentation time. Orange peel waste was used as the substrate for bio-butanol production for the first time and a yield of 19.5 g/L was achieved without addition of nutritional supplements.