Potentials of using mixed culture bacteria incorporated with sodium bicarbonate for hydrogen production from water hyacinth

The aim of this study is to assess the potentials of using mixed culture bacteria incorporated with different concentrations of NaHCO₃ for hydrogen production from water hyacinth (WH). The lowest hydrogen yield (HY) of 30.4 ± 1.9 mL/g_TVS, H₂ content (HC) of 19.5 ± 1.5% and hydrogenase enzyme (HE) activity of 0.06 ± 0.01 mgM.B_reduced/min were registered for the cultures without supplementation of NaHCO₃. The HY, HC, and HE activity were maximized at levels of 69.2 ± 4.3 mL/g_TVS 58.4 ± 3.6% and 0.18 ± 0.01 mgM.B_reduced/min. respectively for the anaerobes supplied with 3.0 g NaHCO₃/L. Furthermore, cellulose, hemicellulose, and lignin destruction efficiencies were 37.2 ± 2.3, 30.0 ± 1.9 and 20.9 ± 1.3% respectively due to the increase of cellulase and xylanase activities up to 2.73 ± 0.17 and 1.87 ± 0.12 U/mL, respectively. Moreover, the abundance of Firmicutes was substantially increased and accounted for 71% of the total OTU's. Microbes belonging to the order Clostridiales and OPB54 were particularly enriched in the medium supplemented with NaHCO₃.