Screening and evaluation of cellulytic fungal strains for saccharification and bioethanol production from rice residue

Abstract

In this study, microwave-assisted alkali and acid pretreated rice straw were used to improve fermentable sugar yield by enzymatic saccharification (ES) employing cellulolytic fungal strains and subsequent bioethanol production by using fermenting yeast. The cellulolytic fungal strains Trichoderma reesei NCIM 1052, 1186, 992, T. reesei ITCC 4025, 6413, Aspergillus niger ITCC 302, A. acculeatus ITCC 5078, A. fumigates ITCC 4768 and Fusarium Solani ITCC 6397 were used for enzymatic saccharification (ES) of acid/alkali pretreated rice straw to optimize the sugar recovery. T. reesei NCIM 1052 was found superior as compared to the other fungal strains in terms of FPase, CMCase activities, and reducing sugars yield from pretreated rice straw. The strains of Saccharomyces cerevisiae NCIM 3186, and Pichia stipitis NCIM 3499 were used for subsequent fermentation to produce bioethanol. The saccharification of alkali pretreated rice straw (2% v/w NaOH) by T. reesei NCIM 1052 resulted in the highest fermentable sugar yield (55.6 g/l) and ultimately, the higher ethanol concentration after 72 h of fermentation with P. stipitis NCIM 3499 (25.3 g/L) as compared to other yeast strains. This study also exhibits the high potential for economic generation of ethanol from rice straw.