초록
<P><B>Abstract</B></P> <P>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 H<SUB>2</SUB> yield of 0.86mol<SUB>H2</SUB>/mol<SUB>lactose</SUB> 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 <I>Clostridiaceae-Lachnospiraceae-Enterobacteriaceae</I>, which performed metabolic pathways co-producing hydrogen. In contrast, long HRT led to the establishment of <I>Sporolactobacillaceae-Streptococcaceae</I> 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.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dark fermentation microbial community was strongly shaped by HRT. </LI> <LI> A maximum volumetric hydrogen production rate of 2000mL/L-d was found at 6h of HRT. </LI> <LI> Two different microbial communities and their interactions were identified. </LI> <LI> Short HRT (6–12h) enriched <I>Clostridiaceae-Lachnospiraceae-Enterobacteriaceae</I>. </LI> <LI> Large HRT (18–24h) negatively affected the performance of dark fermentation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>