Enhancement of volatile fatty acids to extremely high content in fermentation of food waste: Optimization of conditions, microbial functional genes, and mechanisms

[Display omitted] •Effects of pH, temperature, and AS on VFA production from food waste were explored.•In optimal conditions, VFA production accounted for 87.37% of the SCOD.•The NH4+-N content reached 2658.15 mg/L.•Key microorganisms, genes, and enzymes for efficient VFA production were identified.•Expression of genes/enzymes involved in VFA production increased in fermentation. The engineering application of volatile fatty acids (VFA) production from food waste (FW) can significantly enhance resource utilization. Enhancing VFA production is crucial for advancing this engineering application. This study presented a economically-feasible method to achieve high VFA production from FW: Conducting fermentation at pH 9 and 37 ℃ with addition of 20 % anaerobic sludge significantly increased the conversion of FW to VFAs (80.56 g COD/L, accounting for 87.37 % of the soluble chemical oxygen demand), while also increasing the content of NH4+-N (2658.15 mg/L). Macrotranscriptomic sequencing showed that Anaerosalibacter, Amphibacillus, Wansuia, Clostridiisalibacter, unclassified Tissierellia, Massilibacterium, unclassified Bacteroidales, and Tissierellia were the key active microorganisms for VFA production. The expression abundance of functional enzymes and genes related to VFA production pathways increased during the fermentation. This study significantly advanced the practical application of VFA production from FW, offering both theoretical insights and bacterial resources.