Alkali and enzymatic delignification of sugarcane bagasse to expose cellulose polymers for saccharification and bio-ethanol production

To expand the range of natural resources researchers have been re-directing their interests in biomass based bio-fuels, which can be obtained from lignocellulosic biomass. Sugarcane bagasse was pretreated with alkali and ligninolytic enzymes extract produced from Pleurotus ostreatus IBL-02 to depolymerize lignin and expose the cellulose polymers. The de-lignified bagasse was used as substrate for bio-ethanol production in sequential saccharification and fermentation by an indigenous strain of Saccharomyces cerevisiae. Alkali treatment (4% NaOH) and ligninolytic enzymes extract (25 mL) treatment caused 48.7 and 33.6% de-lignification of sugarcane bagasse, respectively. The de-lignified residues were treated with indigenously produced crude cellulase extract from Trichoderma harzaianum that resulted in 69.2 and 72.9% cellulose hydrolysis of alkali and ligninolytic enzymes pretreated bagasse, respectively. S. cerevisea was grown on the hydrolyzates to produce ethanol at 37 degrees C and pH 5.5 that produced 18.2 and 16.3 g/L ethanol using alkali and enzyme pretreated substrates, respectively. For maximum ethanol production, different parameters like fermentation time period, pH, temperature, substrate level and inoculum sizes were optimized using both alkali and enzymes pretreated substrates. Under optimum conditions ethanol production of 32.45 g/L and 28.15 g/L was obtained from alkali and ligninolytic enzymes treated sugarcane bagasse, respectively. In conclusion, the results obtained after high-performance liquid chromatography (HPLC) analysis suggesting ligninolytic pretreatment as a promising tool for bio-ethanol production in sequential saccharification and fermentation. Enzymatic treatment of waste biomass could be of particular interest, since it seems an eco-friendly approach for bio-ethanol production. (C) 2012 Elsevier B.V. All rights reserved.