Characterization and Identification of Cellulose-degrading Bacteria Isolated from a Microbial Fuel Cell Reactor

Abstract

Electricity can be directly biogenerated by bacteria in a microbial fuel cell (MFC) using many different biodegradable wastes as substrate. When cellulose is used as a substrate, the cellulolytic and electrogenic activities require a microbial consortium for energy generation. In this study, cellulose-degrading bacteria were isolated from an MFC using CMC (carboxymethylcellulose) agar medium and their cellulolytic activity was assessed. Cellulolytic bacteria isolated from the MFC were characterized and identified based on their phenotypic characteristics and analysis of their 16S rRNA genes sequence. Of thirty-two isolates, only ten cellulolytic bacterial strains were successfully isolated from the MFC reactor under aerobic conditions. The bacterial isolates had a cellulolytic index between 3.63 to 8.96 U mL-1. The bacterial strain SAM3a demonstrated high identity (99% via 16S-rRNA sequencing) to Staphylococcus saprophyticus which showed the highest CMCase activity (8.96) 0.34U mL-1). Enterobacter cancerogenus JCT-55 showed the next highest CMCase activity (8.34 ± 0.56 U mL-1); S. epidermidis BAB-2554 showed the lowest CMCase activity (3.63) 0.05 U mL-1). In the MFC, the genus Staphylococcus was found to be the most dominant group of cellulose-degrading bacteria which used rice straw as a carbon source. In this study, Escherichia coli, S. saprophyticus, Enterobacter cancerogenus, S. epidermidis, S. hominis, Bacillus subtilis, L. murinus, S. haemolyticus, S. epidermidis, and S. epidermidis were found to possess cellulolytic activity.