Predominance of Bacilli and Clostridia in microbial community of biohydrogen producing biofilm sustained under diverse acidogenic operating conditions

Microbial community structure of acidogenic biofilm from long-term operated sequencing batch bioreactor producing biohydrogen was analyzed through culture independent technique. Bioreactor was operated under variable operation and substrate conditions for a period of 1435 days. Phylogenetic distribution showed a significant diversity and illustrated the presence of four dominant operational taxonomic units (OTUs) viz., Bacteroidia, Bacilli, Clostridia, Flavobacteria and Aquificae. Dominance of Clostridia and Bacilli classes were observed each with four OTUs. Majority of OTUs were found to produce fermentative H2. Even at higher load and under diverse operating conditions bioreactor functioned without any process inhibition which indicates the robustness of sustained microbial community. Community structure of bioreactor was comparatively evaluated with other bioreactor producing H2, operated with same parent culture and conditions but with different substrates, established the dynamics and shift of microbial diversity which corresponded to diverse substrates used for the bioreactor operation.

► Long-term operated H2 producing biofilm reactor was analyzed for microbial community.
► Bacteroidia, Bacilli, Clostridia, Flavobacteria and Aquificae classes were identified.
► Clostridia and Bacilli were found as dominant classes in the acidogenic biofilm.
►  Influence of wastewaters and loading conditions on community structure was observed.
► This study helps to design synthetic consortia for H2 production from wastewaters.