Cloning and characterization of new cellulases from Cellulomonas fimi and Cellulomonas flavigena

Abstract

Lignocellulose is one of the most abundant carbon sources in nature. This naturally-occuring substance is an underutilized source of bioenergy. A major bottleneck in biofuel processing is the enzymatic hydrolysis of lignocellulose into its ultimate fermentable product, glucose. Cellulomonas fimi is a well-studied soil organism known for its capabilities to efficiently hydrolyze cellulose. Recently sequenced genomes of Cellulomonas fimi and Cellulomonas flavigena have allowed analysis to reveal previously unidentified cellulases from several glycoside hydrolase (GH) families. This study also includes the expression of secreted cellulases from families GH 5, 6, and 9 at the protein level by the native organism after growth in media supplemented with carboxymethylcellulose or soluble xylan. In order to find enzymes with novel qualities, the cloning and expression of these newly identified cellulases from C. fimi and C. flavigena were done. One of these enzymes is Celf_1230 (Cel6C), a putative cellobiohydrolase from the glycoside hydrolase family 6. Using substituted cellulose derivatives as substrates, we have characterized Celf_1230 to be a thermostable enzyme with endoglucanase activity.