Bacterial communities in thermophilic H2-producing reactors investigated using 16S rRNA 454 pyrosequencing

In this study, the composition and diversity of the bacterial community in thermophilic H2-producing reactors fed with glucose were investigated using pyrosequencing. The H2-producing experiments in batch were conducted using 0.5 and 2.0 g.l-1 glucose at 55o C. Under the two conditions, the H2 production and yield were 1.3 and 1.6 mol H2/mol glucose, respectively. Acetic, butyric, iso-butyric, lactic and propionic acids were detected in the two reactors. The increase in substrate concentration favored a high H2 yield. In this reactor, a predominance of acetic and iso-butyric acids, 27.7% and 40%, were measured, respectively. By means of pyrosequencing, a total of 323 and 247 operational taxonomic units were obtained, with a predominance of the phylum Firmicutes (68.73 – 67.61%) for reactors with 0.5 and 2.0 g.l-1glucose, respectively. Approximately 40.55% and 62.34% of sequences were affiliated with Thermoanaerobacterium and Thermohydrogenium, microorganisms that produce H2 under thermophilic conditions.