Pilot-scale production of poly-3-hydroxybutyrate-co-3-hydroxyvalerate from fermented dairy manure: Process performance, polymer characterization, and scale-up implications

Abstract Polyhydroxyalkanoate (PHA) production from waste feedstocks using mixed microbial consortia (MMCs) is a promising alternative to conventional commercial production from refined feedstocks with axenic cultures. Prior work has reinforced this potential with nutrient-limited waste feedstocks and stringently controlled operation. The process would be more competitive, however, without these restrictions. To that end, a pilot-scale three-stage feast-famine MMC PHA system using dairy manure was operated with relaxed control for 87 days. All three stages absorbed operational fluctuations and exhibited stable performance comparable to tightly controlled analogs. PHA mass fractions (0.29 to 0.40 g/g; volatile solids basis) approached commercial viability and the purified PHA (21 ± 3% 3-hydroxyvalerate; mole basis) exhibited similarly stable material properties. Finally, characterization of the MMC\u0027s PHA synthesizing capability suggested an innate potential for medium-chain-length monomers. Collectively, these results demonstrate the potential for PHA production from a feedstock without a strict nutrient limitation and the process\u0027s resilience against operational variability.