Biomethane production from sugar beet pulp under cocultivation with Clostridium cellulovorans and methanogens.

This study was demonstrated with a coculture fermentation system using sugar beet pulp (SBP) as a carbon source combining the cellulose-degrading bacterium Clostridium cellulovorans with microbial flora of methane production (MFMP) for the direct conversion of cellulosic biomass to methane (CH). The MFMP was taken from a commercial methane fermentation plant and extremely complicated. Therefore, the MFMP was analyzed by a next-generation sequencing system and the microbiome was identified and classified based on several computer programs. As a result, Methanosarcina mazei (1.34% of total counts) and the other methanogens were found in the MFMP. Interestingly, the simultaneous utilization of hydrogen (H) and carbon dioxide (CO) for methanogenesis was observed in the coculture with Consortium of C. cellulovorans with the MFMP (CCeM) including M. mazei. Furthermore, the CCeM degraded 87.3% of SBP without any pretreatment and produced 34.0 L of CH per 1 kg of dry weight of SBP. Thus, a gas metabolic shift in the fermentation pattern of C. cellulovorans was observed in the CCeM coculture. These results indicated that degradation of agricultural wastes was able to be carried out simultaneously with CH production by C. cellulovorans and the MFMP.