BIOCONVERSION OF HEMICELLULOSE HYDROLYSATE OF SWEET SORGHUM BAGASSE TO ETHANOL BY USING PICHIA STIPITIS NCIM 3497 AND DEBARYOMYCES HANSENII SP.

Production of ethanol from concentrated D-xylose solutions and hemicellulose hydrolysate of sweet sorghum bagasse was achieved by using Pichia stipitis NCIM 3497 and an isolated yeast Debaryomyces hansenii sp. These yeasts were capable of producing ethanol from solutions containing 800 g/L D-xylose, and the optimum sugar concentration was found to be 150 g/L at pH 4, 30oC, with a production time of 72 hours. These yeasts were capable of utilizing multiple sugars. Hemicellulose hydrolysates of sweet sorghum bagasse were obtained by dilute acid hydrolysis and autohydrolysis including steam explosion treatment. The hydrolysate was treated by an over-liming process for detoxification and pH adjustment. Ethanol yield from hemicellulose hydrolysate was found to be higher than that of synthetic medium containing D-xylose. These yeasts can be used in production of ethanol from concentrated hemicellulose hydrolysates containing high pentose sugars obtained while treating lignocellulosic biomass at high substrate concentrations