Development of bacterial systems for the production of cellulase and bioethanol

Abstract

The wide varieties of extant bacterial species are often resistant to various environmental stresses. This demonstrates their frequent ability to adapt to and thrive in challenging environments. One such adaptation in wood-degrading species that may be exploited to produce a product of high value to humans is a more efficient cellulase activity, which may help to overcome current challenges in biofuel production. In this study, 18 efficient cellulase-producing bacteria were isolated from organic fertilizers and paper mill sludges and characterized for consideration in large scale biorefining. All cellulase positive isolates were further characterized to identify those with the greatest cellulase activities for potential industrial application. Six of these isolates produced greater cellulase activity on soluble cellulose in 48 h than the positive control (Cellulomonas xylanilytica). Phylogenetic analysis of a portion of the 16S rDNA gene revealed genera belonging to two major phyla of Gram positive bacteria: Firmicutes and Actinobacteria. Additionally, isolates E2 and E4 (Paenibacillus species) displayed qualitative cellulase activities towards filter paper under limited oxygen condition. When total cellulase activities of E2 and E4 were examined, it was shown that 1% (w/v) carboxymethyl cellulose (CMC) could induce total cellulase activities of 1652 ± 62 and 1457 ± 31 nM of glucose equivalents that were 8- and 5.6-fold greater than total cellulase activities induced by filter paper for E2 and E4, respectively. The genus Paenibacillus includes many highly-expressing cellulase producing strains, and E2 and E4 represent excellent candidates for further cellulase activity analysis and characterization.