Cellulose degradation by one mesophilic strain Caulobacter sp. FMC1 under both aerobic and anaerobic conditions

Caulobacteria are presumed to be responsible for considerable mineralization of organic material in aquatic environments. In this study, a facultative, mesophilic and cellulolytic bacterium Caulobacter sp. FMC1 was isolated from sediments which were taken from a shallow freshwater lake and then enriched with amendment of submerged macrophyte for three months. This strain seemed to evolve a capacity to adapt redox-fluctuating environments, and could degrade cellulose both aerobically and anaerobically. Cellulose degradation percentages under aerobic and anaerobic conditions were approximately 27% and 10% after a 240-h incubation in liquid mediums containing 0.5% cellulose, respectively. Either cellulose or cellobiose alone was able to induce activities of endoglucanase, exoglucanase, and β-1,4-glucosidase. Interestingly, ethanol was produced as the main fermentative product under anaerobic incubation on cellulose. These results could improve our understanding about cellulose-degrading process in aquatic environments, and were also useful in optimizing cellulose bioconversion process for bioethanol production.