Effect of operational pH on biohydrogen production from food waste using anaerobic batch reactors

This study was performed to investigate the influence of operational pH on dark H-2 fermentation of food waste by employing anaerobic batch reactors. The highest maximum H-2 yield was 1.63 mol H-2/mol hexoseadded at operational pH 5.3, whereas the lowest maximum H-2 yield was 0.88 mol H-2/mol hexoseadded at operational pH 7.0. With decreasing operational pH values, the n-butyrate concentration tended to increase and the acetate concentration tended to decrease. The highest hydrogen conversion efficiency of 11.3% was obtained at operational pH 5.3, which was higher than that (8.3%) reported by a previous study (Kim et al. (2011) 'Effect of initial pH independent of operational pH on hydrogen fermentation of foodwaste', Bioresource Technology 102 (18), 8646-8652). The new result indicates that the dark fermentation of food waste was stable and efficient in this study. Fluorescence in situ hybridization (FISH) analysis showed that Clostridium species Cluster I accounted for 84.7 and 13.3% of total bacteria at operational pH 5.3 and pH 7.0, respectively, after 48 h operation.