11-16: Growth media optimization for polyhydroxyalkanoate and hydrogen coproduction from Rhodospirillum rubrum cultured on synthesis gas

The typical biorefinery separates biomass into cellulose, hemicellulose, lignin, and terpenes before processing each component into fuels and chemicals.  In a hybrid biorefinery, thermochemical processes first break down recalcitrant components of the biomass into intermediate compounds that can be processed biologically.  One such hybrid biorefinery is based on synthesis gas fermentation.  This process begins with the gasification of biomass to produce syngas, a flammable gas mixture consisting primarily of carbon monoxide (CO), hydrogen (H₂), and carbon dioxide (CO₂). Microorganisms are then used to ferment the syngas into biofuels and chemicals.  Rhodospirillum rubrum, a non-sulfur purple bacterium, utilizes the carbon monoxide (CO) in syngas to produce hydrogen, a high fuel value gas, and polyhydroxyalkanoates (PHA), biobased-biodegradable polymers.  Information is limited pertaining to the optimization of growth media for R. rubrum for its effect on the coproduction of H₂ and PHA.  This investigation examines growth medium optimizations considering both cost of media components and the coproduction of H₂ and PHA.  Correlations of PHA production to cell density at different growth stages are also examined.