Polyhydroxyalkanoates (PHA) are microbially synthesized polyesters, accumulated intracellularly as a carbon and energy storage reserve. Fermenting PHA from low cost waste streams represents an opportunity to produce the thermoplastic at a market ready price. PHA is known to be formed in activated sludge from municipal wastewater treatment processes, however the amount of carbon PHA biosynthesis in raw activated sludge/wastewater is limited. Micromidas has developed a series of processes including acidogenic fermentation of renewable feedstocks, such as municipal wastewater biosolids, manure, and food wastes, to generate volatile fatty acids (VFA)-rich feed for PHA production. Selection and enrichment of PHA-producing bacteria with high PHA-accumulating capacities was also conducted in feast-famine sequencing reactors. On-going development includes using multi-stage continuous processing  to perform bacterial growth and PHA production at high productivity as well as a high content in biomass. The selected microbe species in conjunction with the delivered profile of fatty acids from the digestion environment gives polyhydroxybutyrate-co-valerate (PHBV) copolymers with valerate monomer compositions up to 22%. This copolymer composition enables melting to occur well below the material's decomposition temperature, overcoming a process limitation that has been common to many PHAs in the market to date.

Polyhydroxyalkanoate biosynthesis from volatile fatty acids derived from waste feedstocks

244th National Meeting (2012)

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