초록
<P><B>Abstract</B></P> <P>Dark fermentative biohydrogen production in a thermophilic, xylose-fed (50 mM) fluidised bed reactor (FBR) was evaluated in the temperature range 55–70 °C with 5-degree increments and compared with a mesophilic FBR operated constantly at 37 °C. A significantly higher (p = 0.05) H<SUB>2</SUB> yield was obtained in the thermophilic FBR, which stabilised at about 1.2 mol H<SUB>2</SUB> mol<SUP>−1</SUP> xylose (36% of the theoretical maximum) at 55 and 70 °C, and at 0.8 mol H<SUB>2</SUB> mol<SUP>−1</SUP> xylose at 60 and 65 °C, compared to the mesophilic FBR (0.5 mol H<SUB>2</SUB> mol<SUP>−1</SUP> xylose). High-throughput sequencing of the reverse-transcribed 16S rRNA, done for the first time on biohydrogen producing reactors, indicated that <I>Thermoanaerobacterium</I> was the prevalent active microorganism in the thermophilic FBR, regardless of the operating temperature. The active microbial community in the mesophilic FBR was mainly composed of <I>Clostridium</I> and <I>Ruminiclostridium</I> at 37 °C. Thermophilic dark fermentation was shown to be suitable for treatment of high temperature, xylose-containing wastewaters, as it resulted in a higher energy output compared to the mesophilic counterpart.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thermophilic FBR (55–70 °C) yielded 1–2 fold more H<SUB>2</SUB> than mesophilic FBR (37 °C). </LI> <LI> Next-generation sequencing of cDNA was used for the first time on dark fermentation. </LI> <LI> <I>Thermoanaerobacterium</I> dominated the active microbial community at 55–70 °C. </LI> <LI> In the thermophilic FBR, <I>Clostridium</I> caused unstable H<SUB>2</SUB> yield only at 65 °C. </LI> <LI> At 37 °C, VFA accumulation and homoacetogenesis caused unstable H<SUB>2</SUB> yield. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>