Bioethanol production from alkaline hydrogen peroxide pretreated Populus deltoides wood using hydrolytic enzymes of Bacillus stratosphericus N12(M) and Bacillus altitudinis Kd1(M) under different modes of separate hydrolysis and fermentation by monoculture and co-culture combinations of ethanologens

Abstract

An integrated approach was studied for in-house cellulase and xylanase production, from novel hyper hydrolytic enzyme producers and enzymatic hydrolysis of pretreated Populus deltoides wood into bioethanol. A xylanase producer Bacillus altitudinis Kd1 (M) and cellulase producerBacillus stratosphericus N12 (M) was isolated from soil. Optimization of process parameters led to an optimal xylanase activity of 96.25 IU at 300C and pH 5.5 and cellulase activity of 5.98 IU at 300C and pH 8.0. The NaOH+H2O2 pretreated biomass was hydrolysed using cellulase and xylanase producing 12.45 mg/g of reducing sugars. Further fermentation of lignocellulosic hydrolysate was performed using different yeasts viz. Saccharomyces cerevisiae I, Saccharomyces cerevisiae II, Pichia stipitis, Candida shehatae and Zymomonas mobilis and maximum 11.10 g/l ethanol yield achieved with co-culture of S. cerevisiae II + P. stipitis with fermentation efficiency of 43.52% under method IV of SHF. The results have significant implications and further applications regarding production of fuel ethanol from agricultural lignocellulosic waste.