Deciphering the operation efficiency and fermentation model in mixed microbial cultures system for...

The polyhydroxyalkanoates (PHAs) synthesis craft by using diversified organic acids from anaerobic fermentation was restricted due to the poor compatibility and uncertain biopolymer types. Odd-chain VFAs favor the accumulation of co-polyesters. In this study, propionic and valeric acids were utilized as substrates for mixed microbial cultures (MMC) acclimation, in the expectation of synthesizing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with exceptional properties. Bioreactors using propionic acid and valeric acid as carbon substrates are defined as MMC-P and MMC-V, respectively. The acquisition of core PHAs communities was conducted under a feast-famine model, characterized by elevated carbon-nitrogen ratios (C/N) and increased organic loading. The optimum PHBV reached 616.47 mg L^-1 (MMC-P, C/N = 60) and 406.68 mg L^-1 (MMC-V, C/N = 80), accordingly. Allosphingosinicella, Labilithri, Stenotrophomonas, Brevundimonas, Parvibaculum, Azospirillum, and Hydrogenophaga were identified as the core PHBV fermentation consortium. The functional enzymes related to fatty acids β-oxidation and PHBV synthesis were concentrated. Four categories of PHAs synthases have been targeted for the production of multiple biopolymers. This study presented a technical reference for a convenient biomanufacturing process for efficient utilization of odd-chain organic waste.