Hydrogen-producing facultative anaerobic bacteria isolated from kitchen wastewater for sustainable bioenergy...

Hydrogen production through dark fermentation is a promising alternative to clean energy. In this study, kitchen wastewater was used to isolate hydrogen-producing bacteria. Three pretreatment techniques acid pretreatment, heat pretreatment, and freezing and thawing pretreatment, were applied to suppress methanogenic bacteria and enrich hydrogen-producing microbial populations. To evaluate the bacterial populations of untreated and treated kitchen wastewater using the spread plate method. Among the 41 bacterial isolates obtained, the bacterial strains were screened by the Hungate method with glucose as a substrate. A total of 11 bacterial strains produced the gas and were identified by morphological and biochemical characterization. The hydrogen production efficiency of one strain was significantly higher than that of the others. The 16S rRNA molecular sequencing confirmed the identification of the selected hydrogen-producing organisms as Lactobacillus crispatus. After pretreatment with acid, heat, and freeze-thaw, different bacterial isolates were isolated from kitchen wastewater. A strain recovered from the freeze-thaw pretreatment demonstrated the highest hydrogen-producing potential and was identified as Lactobacillus crispatus. The strain produced a maximum biohydrogen yield of 109.7 mL H₂/L. In a low-cost microbial fuel cell, the isolated strain achieved a maximum voltage output of 0.63 V per cell within 24 h, demonstrating its capability for bioelectricity generation. Lactobacillus crispatus has the potential to serve as an effective biological agent for hydrogen production. Pretreatment strategies involving freeze-thaw were especially effective in enriching hydrogen-producing bacteria in kitchen wastewater. Overall, this study demonstrates that optimized pretreatment of wastewater combined with selective microbial screening can enhance hydrogen production and offers a sustainable approach for renewable energy generation.