Comparative analysis of H2 production and microbial communities during dark fermentation of food waste under varying temperature and cultivation modes

Abstract

This study conducted a comparative analysis of hydrogen (H₂) production and bacterial community dynamics from food waste as a substrate under mesophilic (37 °C) and thermophilic (50 °C) conditions using batch and fed-batch cultivation. The modified Gompertz model was used to evaluate H₂ production characteristics, and bacterial metagenomic analysis was conducted to assess bacterial community dynamics under different cultivation conditions. In batch cultures, thermophilic conditions exhibited superior H₂ production potential (P) and maximum production rate (R_m) compared to mesophilic conditions. Notably, the thermophilic second batch culture achieved the highest P value of 775 mL·L⁻¹ and an R_m of 99 mL·L⁻¹·h⁻¹. Bacterial community analysis revealed that Clostridium was the dominant H₂ producer under mesophilic conditions, whereas thermophilic conditions supported a more diverse bacterial consortium, including Clostridium, Caldibacillus, Caproicibacter, and Caproiciproducens. This shift in dominant bacteria led to higher H₂ production compared to mesophilic conditions. Similarly, in fed-batch cultivation, thermophilic conditions outperformed mesophilic conditions in H₂ production. This enhancement is attributed to higher bacterial diversity and effective mitigation of inhibitory effects caused by substrate accumulation and byproducts in fed-batch systems. These findings contribute to advancing sustainable energy production systems from food waste and provide insights into optimizing dark fermentation processes. Future research should focus on refining substrate feeding strategies, improving reactor designs, and further exploring the relationship between bacterial community dynamics and H₂ production efficiency.