Biohydrogen production from wastewater-grown microalgae-bacteria consortia: Optimizing inoculum selection for enhanced yield

The rising demand for renewable energy and sustainable waste management has encouraged interest in biohydrogen (bioH2) as a clean energy source. This study aimed to assess the potential of microalgae-bacteria consortia biomass (MBCB) as an inoculum for bioH2 production. MBCB, cultivated in high-rate algal ponds (HRAPs) treating domestic wastewater, was used to produce bioH2. Natural fermentation (NF) was applied to both raw (RB) and thermally pretreated biomass (PB) for 5, 10, and 15 days to optimize microbial selection. Biohydrogen production potential (BHP) and microbial dynamics were evaluated. Thermal pretreatment enhanced bioH2 yield but prolonged the lag phase and lowered production rates. RB fermented for 5 days (RB-5) achieved the highest bioH2 production rate (1.25 ± 0.08 mmol H2 h−1). Microbial analysis revealed higher diversity in RB than PB, with PB selecting thermoresistant microorganisms like Clostridia. NF promoted shifts in microbial communities, favoring fermentative bacteria. These findings underscore the promise of using MBCB as inoculum for bioH2 production and demonstrate the viability of integrating NF and MBCB for renewable energy generation from wastewater biomass. However, additional economic and environmental evaluations are required to confirm feasibility at larger scales.