3.4. Relationship between process disturbances and bacterial communities
Fig. 4. Properties of microbial ABT-538 changes and their metabolites. (A) Distribution of class level bacteria and (B) trends of organic acids.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 5. Phylogenetic tree of observed OTUs and associated heat-map information (P1; startup, P2; HRT of 12 h, P3; shock loading, P4; acidification, P5; HRT of 8 h, P6; starvation, and P7; alkalization sample).Figure optionsDownload full-size imageDownload as PowerPoint slide
Gammaproteobacteria were also dominantly detected together with Clostridia and Bacilli, the proportion of which fluctuated with operational time ( Fig. 4 and Fig. 5). Phylogenetic analysis identified that a significant proportion of the bacteria within the Gammaproteobacteria showed close affiliation with Enterobacter and Pantoea species. These species were also reported to produce biohydrogen via dark fermentation ( Kumar and Das, 2000 and Zhu et al., 2008). It is reasonable to deduce that the co-occurrence of Clostridia and non-clostridial biohydrogen producers (e.g., Enterobacter and Pantoea) during operation of our reactor positively affected biohydrogen production, judging from previous reports about enhanced biohydrogen production by co-culturing two groups of bacteria that are able to produce biohydrogen.