Photoheterotrophy for economical production of bioplastics from municipal organic waste: Integration of polyphosphate metabolism and P-recovery chemistry to maximize PHA yields

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The municipal wastewater and organic solids waste industries are undergoing a resource recovery revolution. Producing useful biomaterials from wastes promises great economic and environment benefits. Important biomaterials to produce include the bioplastic precursor polyhydroxyalkanoate (PHA), and the phosphorus (P) mineral carbonate apatite (i.e., phosphate rock) used in fertilizers. We will develop a new highly efficient mixed microbial process harnessing infrared-using photoheterotrophic purple non-sulfur bacteria (PNSB) to synthesize PHA and concentrate P; then, to apply crystallization theory for P capture. Current techno-economic studies of PHA production suggest that mixed cultures are more economical than pure cultures fed sterilized feedstocks. Thus, our project will provide cost reduction, and end-product versatility. Our industrial partner will gain new knowledge of PNSB-based disruptive technologies to continue developing future product lines with several market outlets for recovered resources. Canadian wastewater treatment facilities will gain an efficient resource recovery processes adapted to cold winters. Canada would also benefit from a renewable source of P for fertilizer production, as the only Canadian phosphate mine closed in 2013. These new processes will help reduce greenhouse gas emissions and help Canada meet its sustainability and food security targets. The proposed process will take advantage of the efficient photoherotrophic PNSB metabolism to concentrate phosphate and produce biomass from dilute municipal wastewater. The PNSB biomass grown in wastewater will be enriched for PHA accumulation using a new high intensity illumination method, which will also induce the accumulation of polyphosphate. In a separate step, the polyphosphate will be released from the PNSB and captured by a new carbonate apatite crystallization process. The P-limited biomass will be used for PHA synthesis using volatile fatty acids generated from the fermentation of organic waste. The proposed research will elucidate the proper reactor conditions to maximize the PHA and polyphosphate accumulation metabolisms by PNSB. The project will train a total of 12 HQP: 2 PhD, 3 MEng, 1 postdocs, and 6 undergrads.