Volatile fatty acids production from saccharification residue from food waste ethanol fermentation: Effect of pH and microbial community

•VFAs production from RSCFW favored butyric acid with pH controlled.•The highest VFAs concentration was 172.4 ± 6.2 mg/g VS at pH 6.5.•Microbial community showed the dominant bacteria for acetic to butyric. In this study, residue from saccharification and centrifugation of food waste ethanol fermentation was used as substrate to produce volatile fatty acids. The effects of different pH (5.5, 6.5, and uncontrolled) on the VFAs concentration, composition, acidogenic efficiency and microbial community distribution were investigated. The results showed that the highest concentration of VFAs was 267.8 ± 8.9 mg COD/g VS at pH of 6.5, and the highest percentage of butyric acid (79.8%) was followed by propionic acid and acetic acid at the end of the reaction. Microbial analysis showed that the contents of Vagococcus and Actinomyces increased, while the contents of Bacteroides and Fermentimonas decreased during anaerobic fermentation. The comparative high pH induced the accumulation of butyric acid. This study provides a new idea for the step anaerobic fermentation of food waste to produce alcohol and acid simultaneously.