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Dark-fermentative biohydrogen pathways and microbial networks in continuous stirred tank reactors: Novel insights on their control

Palomo-Briones, Rodolfo, Razo-Flores, Elías, Bernet, Nicolas, Trably, Eric
Applied energy 2017 v.198 pp. 77-87
bacteria, biochemical pathways, biohydrogen, fermentation, hydrogen production, lactic acid, metabolites, microbial communities
In the present work, the influence of hydraulic retention time (HRT) on dark fermentation metabolism was evaluated through the operation and analysis of a series of four continuous stirred tank reactors (CSTR) at four HRT ranging from 6h to 24h. A maximum volumetric hydrogen production rate (VHPR) of 2000±149mL/L-d corresponding to an H2 yield of 0.86molH2/mollactose was observed at 6h HRT. In depth analysis of metabolite profiles and microbial communities showed that low values of HRT favored the emergence of a community dominated by Clostridiaceae-Lachnospiraceae-Enterobacteriaceae, which performed metabolic pathways co-producing hydrogen. In contrast, long HRT led to the establishment of Sporolactobacillaceae-Streptococcaceae microbial community that outcompeted hydrogen producing bacteria and was responsible of lactate production. Results suggested that these two communities mutually excluded themselves and HRT can act as an operational parameter to control the microbial communities and consequently the related metabolic pathways.