Dynamic changes in community structure and degradation performance of a bacterial consortium MMBC-1 during the subculturing revival reveal the potential decomposers of lignocellulose.

Bacterial consortium is an important source of lignocellulolytic strains, but it is still a challenge to distinguish the direct decomposers of lignocellulose from other bacteria in such a complex community. This study aims at addressing this issue by focusing on the dynamic changes in community structure and degradation activity of MMBC-1, an established and stable lignocellulolytic bacterial consortium, during its subculturing revival. MMBC-1 was cryopreserved with glycerol as a protective agent and then inoculated for revival. Its enzyme activities for degradation recovered to the maximum level after two rounds of subculturing. Correspondingly, the cellulose and hemicellulose in lignocellulosic carbon source were gradually decomposed during the revival. Meanwhile, the initial dominant bacteria represented by genus Clostridium were replaced by the bacteria belonging to Lachnospira, Enterococcus, Bacillus, Haloimpatiens genera and family Lachnospiraceae. However, only three high-abundance (> 1%) operational taxonomic units (OTUs) (Lachnospira, Enterococcus and Haloimpatiens genera) were suggested to directly engage in lignocellulose degradation according to correlation analysis. By comparison, many low-abundance OTUs, such as the ones belonging to Flavonifractor and Anaerotruncus genera, may play an important role in degradation. These findings showed the dramatic changes in community structure that occurred during the subculturing revival, and paved the way for the discovery of direct decomposers in a stable consortium.