Characterization of extracellular and substrate-bound cellulases from a mesophilic sugarcane bagasse-degrading microbial community

Sugarcane bagasse (SCB) is a residual product of sugar processing, containing mainly lignocellulose. The biodegradation of cellulose is an economical approach to recycling SCB. To obtain an effective microbial community and study the SCB biodegradation process, a SCB-degrading mesophilic microbial community, EMSD13, growing at 50 °C was isolated. More than 77% of alkali pretreated SCB was degraded and over 83% of the cellulose it contained was utilized by the EMSD13 community within 6 days. To understand the biodegradation procedure of EMSD13, extracellular and SCB-absorbable cellulases were analyzed. The peak activity (42 mU/mL) of the extracellular cellulase in the supernatant occurred on the 3rd day of incubation. About 73.6 mg of substrate-bound proteins with a cellulase activity of 61.1 mU/mg were recovered from residual SCB by eluting with 3 M guanidine hydrochloride. Also, 15.9 mg of proteins with 28.6 mU/mg of cellulase activity were obtained from residual SCB by eluting with 6 M urea. SDS-PAGE analysis showed that cellulases in both elutes were similar, but most differed from those in the supernatant. This is the first report on substrate-bound cellulases from a microbial community.