Continuous lignocellulosic ethanol production using Coleus forskohlii root hydrolysate

Root biomass of Coleus forskohlii obtained after extraction of forskolin constitutes more than 90% of the raw material rich in carbohydrates that could be used as a substrate for the production of bioethanol. Ethanol production from this waste biomass was optimized in batch and continuous fermentation. The maximum ethanol concentration of 31.32 g/l was obtained with batch fermentation. Continuous production of ethanol was carried out using wood chips immobilized cells of Saccharomyces cerevisiae in packed bed reactor. The maximum ethanol concentration of 34.25 g/l was obtained with nitrogen supplement and aeration as compared to 33.57 g/l without supplement and aeration at 0.1 (1/h) dilution rate showing no effect of aeration and nitrogen at low dilution rate. The maximum ethanol productivity (15.88 g/l h) was obtained at a dilution rate of 1 (1/h) with nitrogen supplement and aeration whereas ethanol productivity (13.48 g/l h) was obtained at a dilution rate of 0.75 (1/h) without nitrogen supplement and aeration showing promising effect of nitrogen and aeration at high dilution rate. Immobilized column reactor was useful for the production of bioethanol, and also suggests efficient utilization of C. forskohlii root biomass for the production of bioethanol.