The effects of temperature and organic load rate (OLR) stress on dark fermentative hydrogen production from food wastes (FW) were investigated through analysis of shaping metabolic pathways, microbial communities and energy balance in the long-term hydrogen production systems. The gas production rate (GPR) of 9.32 mL/g VS·h and hydrogen proportion of 58.19% were reached with 6 g VS/L·d under thermophilic condition. In depth analysis of metabolite profiles and microbial communities showed that thermophilic fermentation favored a stable community dominated by Thermoanaerobacterium, which was in the ascendant with increasing of OLR. In contrast, mesophilic fermentation led to ever changing microbial community comprised Lactobacillus, Olsenella, Caproiciproducens, Roseburia, Streptococcus, performed low hydrogen production, high butyric and acetic acids concentrations in long-term system. The energy assessment showed the higher energy recovery rate was obtained in thermophilic fermentation than that of the mesophilic system. Results suggested that stability and shock resistance capability of microbial community are crucial elements related hydrogen production and metabolic pathways.
Keywords hydrogen production; metabolic pathways;microbial community; dark fermentation; long-term;food wastes