초록
<P><B>Abstract</B></P> <P>This study investigated the utilization of <I>Pistia stratiotes</I> for biohydrogen production via a dark-fermentation process. The aquatic plant was subjected to acid-hydrolysis using H<SUB>2</SUB>SO<SUB>4</SUB>: 3.0% (v/v) for 40 min, resulting in sugar yield: 122.2 ± 5.2 mg/g. The optimum culture pH was 5.5, achieving hydrogen yield (HY): 2.46 ± 0.14 mol-H<SUB>2</SUB>/mol-glucose (3.51 ± 0.20 mg-H<SUB>2</SUB>/g-dry weight) at fermentation time 8 h, temperature 25 °C, and substrate-to-biomass (S/X) ratio 1.0 g-COD/g-VSS. The organic mass balance (92–96%) and electron-equivalent balance (92–98%) indicated the reliability of fermentation data. The dominant species included <I>Planctomycetales</I>, <I>Verrucomicrobiales</I>, <I>Clostridiaceae</I>, and <I>Gammaproteobacteria</I>. The phylogenetic analysis confirmed the abundance of hydrogen-producing bacteria such as <I>Bacillus</I>, <I>Clostridium</I>, and <I>Enterobacter</I>. The hydrogenase gene expression provided the highest activity at pH: 5.5 with a cell number 2.53 × 10<SUP>4</SUP> copies/ng-DNA compared to pH: 4.5 (6.95 × 10<SUP>3</SUP> copies/ng-DNA) and pH: 8.5 (7.77 × 10<SUP>3</SUP> copies/ng-DNA). The total cost of the fermentation system including the amortization cost of investment and operating cost was 0.08 $/kg-dry weight (22.8 $/kg-H<SUB>2</SUB> produced).</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>Pistia stratiotes</I> was acid-hydrolyzed for bioH<SUB>2</SUB> production via dark fermentation. </LI> <LI> Optimum pH of 5.5 achieved HY: 2.46 mol-H<SUB>2</SUB>/mol-glucose at 8 h, and 25 °C, and S/X: 1.0. </LI> <LI> Electron-equivalent balance was 92–98%, and COD mass balance was 92–96%. </LI> <LI> Microbial analyses using FISH, PCR, and qPCR confirmed the H<SUB>2</SUB> productivity results. </LI> <LI> The cost of fermentation system was 0.08 $/kg-dry weight of <I>Pistia stratiotes</I>. </LI> </UL> </P>