Food waste fermentation was investigated in a leach bed reactor operated at acidic, neutral and alkaline conditions. Highest solids reduction of 87% was obtained at pH 7 in 14 days of reaction time with minimum mixing. The concentration of volatile fatty acids increased to 28.6 g COD/L under pH 7, while the highest butyric acid of 16 g COD/L was obtained at pH 6. Bacterial community structure was narrowed down to Bifidobacterium and Clostridium at pH 6, while Bacteroides and Dysgonomonas were identified as main players at both pH 7 and 8. Bacterial populations in the food residue generally reflected those in the leachate, but some bacteria were selectively enriched in the leachate or the food residue. Bacterial community dynamics suggested that biodegradable food waste was first fermented by one of dominant players (e.g., Clostridium) and the other degraded resistant dietary fibers later (e.g., Bifidobacterium, Bacteroides, Dysgonomonas).