Bioconversion of waste activated sludge hydrolysate into polyhydroxyalkanoates using Paracoccus sp. TOH: Volatile fatty acids generation and fermentation strategy

•The feasibility of PHAs synthesis with hydrolysate derived from WAS was verified.•The optimum cumulative yield of VFAs was 4067.6 mg-COD·L−1 at lysozyme treatment.•Microbial consortia involved in VFAs fermentation were enriched.•The number of functional genes related to substrates metabolism was increased.•PHBV (119.1 mg·L−1) containing 20.3 mol% 3HV was obtained from the VFAs stream.