Identification and Characterization of an Anaerobic Ethanol-Producing Cellulolytic Bacterial Consortium from Great Basin Hot Springs with Agricultural Residues and Energy Crops

In order to obtain the cellulolytic bacterial consortia, sediments from Great Basin hot springs (Nevada, USA) were sampled and enriched with cellulosic biomass as the sole carbon source. The bacterial composition of the resulting anaerobic ethanol-producing celluloytic bacterial consortium, named SV79, was analyzed. With methods of the full-length 16S rRNA library-based analysis and denaturing gradient gel electrophoresis, 21 bacteria belonging to eight genera were detected from this consortium. Clones with closest relation to the genera Acetivibrio, Clostridium, Cellulosilyticum, Ruminococcus, and Sporomusa were predominant. The cellulase activities and ethanol productions of consortium SV79 using different agricultural residues (sugarcane bagasse and spent mushroom substrate) and energy crops (Spartina anglica, Miscanthus floridulus, and Pennisetum sinese Roxb) were studied. During cultivation, consortium SV79 produced the maximum filter paper activity (FPase, 9.41 U/ml), carboxymethylcellulase activity (CMCase, 6.35 U/ml), and xylanase activity (4.28 U/ml) with sugarcane bagasse, spent mushroom substrate, and S. anglica, respectively. The ethanol production using M. floridulus as substrate was up to 2.63 mM ethanol/g using gas chromatography analysis. It has high potential to be a new candidate for producing ethanol with cellulosic biomass under anoxic conditions in natural environments.