Acid tolerance response (ATR) of microbial communities during the enhanced biohydrogen process via cascade acid stress

•Enhanced biohydrogen production via cascade acid stress was investigated.•Structure pattern of microbial communities was adapted with acid stress.•Both acid tolerant strain and biohydrogen producers got enriched after acid stress.

Enhanced biohydrogen production via cascade acid stress on microbial communities, structure patterns of the microbial communities revealed by PLFAs, and the succession of biohydrogen related species against cascade acid stress were all investigated. It was found that hydrogen production could be improved from 48.7 to 79.4 mL/gVS after cascade acid stress. In addition, the Gram negative (G−) bacteria were found to be more tolerant to organic acids than those of the Gram positive (G+) bacteria, regardless of the dominance of G+ bacteria within the microbial communities. Moreover, Clostridium butyricum, Clostridium aciditolerans and Azospira oryzae, were proved to be enriched, and then might play indispensable roles for the enhanced biohydrogen production after cascade acid stress, as which were responsible for the biohydrogen accumulation, acid tolerance and nitrogen removal, respectively.