Isolation of Cellulolytic Organisms from the Gut Contents of Termites Native to Nepal and Their Utility in Saccharification and Fermentation of Lignocellulosic Biomass

Abstract

Lignocellulose is one of the most abundant renewable materials that could serve as a source for fermentable sugars. However, its commercial deployment is limited by the fact that lignocellulose is recalcitrant and requires heroic efforts to release sugars. Although very few, there are cellulose degrading organisms in nature that can efficiently degrade the cellulosic biomass and one among them is termite. Termites are responsible for mass turnover of the cellulosic biomass and they accomplish this task by harbouring a consortium of cellulolytic and lignolytic microorganisms. In the present study, we have isolated eight bacterial and five fungal cellulose degrading organisms from the gut of a termite native to Nepal via basal culture medium enrichment with filter paper as substrate. The isolated organisms were identified as Bacillus sp., Cellulomonas sp., Enterobacter sp., and Aspergillus sp. The Congo red screening assay for cellulase production showed the largest zone of hydrolysis (38 mm) for Aspergillus sp. The carboxymethyl cellulose assay revealed that the Bacillus sp (S3B8; 0.12 0.01 IU/ml obtained within96 hours) and Aspergillus sp. (S3F3; 0.07 0.01 IU/ml obtained within 168 hours) were most efficient cellulase producers. The saccharification and fermentation of lignocellulosic biomass to ethanol was successfully achieved via culturing of selected bacterial [Bacillus (S3B8)] and fungal isolates [Aspergillus (S3F3)] and then fermentation with Saccharomyces cerevisiae (S2Y1). Further characterization of these organisms and optimization of fermentation of lignocellulosic biomass is ongoing.