Enhanced biohydrogen production from food waste using immobilized Enterococcus faecalis isolate VT-H1

The development of sustainable biohydrogen production systems is essential for advancing renewable energy technologies. This study evaluates immobilized Enterococcus faecalis VT-H1 for hydrogen generation from food waste under mesophilic conditions. Microbial cells were entrapped in calcium alginate beads, and the effects of alginate concentration and inoculum density were systematically optimized. Scanning electron microscopy confirmed successful immobilization and cell proliferation within the matrix, correlating with enhanced hydrogen production kinetics. Optimal conditions (2% w/v alginate, OD600 of 1.0) achieved a maximum hydrogen production rate of 0.040 mol H2/mol glucose·h and shortened the lag phase. Reusability tests demonstrated stable hydrogen yields across three consecutive cycles. When applied to sucrose and real food waste, the immobilized system significantly outperformed suspended cultures, yielding up to 101.3 mL H2/gVS at 20 gVS/L. Volatile fatty acid profiling indicated butyrate as the dominant metabolite linked to optimal hydrogen yields, whereas excess substrate loading led to VFA accumulation and reduced performance. Techno-economic analysis suggested greater cost efficiency due to inoculum reusability despite slightly lower batch yields. Overall, immobilized E. faecalis VT-H1 offers a robust and economically viable platform for food waste valorization, integrating renewable energy production with circular bioeconomy strategies.