Hydrogen fermentation of food waste by alkali-shock pretreatment: Microbial community analysis and limitation of continuous operation

In the study, at first, batch tests were performed to investigate the effect of alkali-shock on H2 production from food waste (FW). After alkali-pretreatment of FW at pH 9.0–13.0, the FW was cultivated under mesophilic condition at pH 6.0 for 30 h without external inoculum addition. The amount of H2 production from FW pretreated at pH 11.0 and 12.0 was higher than that achieved in other pretreatment pH. The main metabolite was butyrate, and Clostridium were dominant at pH 11.0 and 12.0. Meanwhile, lactate was the main metabolite with Enterococcus and Streptococcus being the dominant genus at other pretreatment pH. When the batch process was switched to a continuous mode, H2 production was significantly dropped due to the increased activity of H2-consumers. The reliability of alkali-pretreatment at pH 11.0 was proven by repeating the scale-up batch process, recording 1.57 ± 0.11 mol H2/mol hexoseadded (17 ± 2 L H2/kg FW) and 4.39 ± 0.32 L H2/L/d.