초록
<P><B>Abstract</B></P> <P>In this study, mixed and pure bacterial cultures are inoculated in a dark-fermentation process for hydrogen production from <I>Pistia stratiotes</I> hydrolysate. The maximum hydrogen yield (HY) of 2.3 mol<SUB>H₂</SUB>/mol<SUB>glucose</SUB> (energy yield 0.3 kJ/g<SUB>DW</SUB>) is obtained at pH 5.5, fermentation time 6.7 h, substrate-to-biomass ratio (S/X) 0.5 g<SUB>COD</SUB>/g<SUB>VSS</SUB>, and 25 °C using a mixed culture system. The plots of HY versus pH and time result in quadratic linear concave-up curves, whereas the effects of S/X and temperature on HY cause quadratic concave-up and flat curves, respectively. Fluorescent <I>in situ</I> hybridization (FISH) indicates that the mixed culture contains multiple H<SUB>2</SUB>-producers including <I>Enterobacteriaceae</I>, <I>Gammaproteobacteria</I>, <I>Betaproteobacteria</I>, and <I>Clostridium histolyticum</I>. Three isolates belonging to <I>Bacillus cereus</I>, <I>Bacillus anthracis</I>, and <I>Enterobacter cloacae</I> are used as pure cultures, achieving HYs of 2.21, 1.10, and 1.97 mol<SUB>H₂</SUB>/mol<SUB>glucose</SUB>, respectively. Accordingly, the mixed culture inoculum subjected to thermal treatment at 100 °C for 30 min can deliver higher HYs than pure cultures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>Pistia stratiotes</I> (aquatic plant) was utilized for H<SUB>2</SUB> production by dark-fermentation. </LI> <LI> Mixed culture achieved 2.3 mol<SUB>H₂</SUB>/mol<SUB>glucose</SUB> at pH 5.5, 6.7 h, S/X 0.5 g<SUB>COD</SUB>/g<SUB>VSS</SUB>, 25 °C. </LI> <LI> Mixed culture contained <I>Enterobacteriaceae</I>, <I>Betaproteobacteria</I>, and <I>C. histolyticum</I>. </LI> <LI> Bacterial strains were extracted from thermal-treated mixed culture for H<SUB>2</SUB> production. </LI> <LI> <I>B. cereus</I>, <I>B. anthracis</I>, <I>E. cloacae</I> pure cultures achieved HYs 2.2, 1.1, 2.0 mol/mol. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>