Growing attention on the economic and environmental liabilities associated with petroleum feedstocks has highlighted a need to develop alternative feedstocks and processes that are both sustainable and environmentally friendly.  In our laboratory we are working to meet this challenge by developing a bioprocess platform based on the microorganism, Ralstonia eutropha.  This versatile organism can be grown on sugar and O2, or it can be grown autotrophically, using a mixture of CO2, H2, and O2. Initially we are focusing on the biopolymer, PHB-co-PHV (polyhydroxybutyrate-co-polyhydroxyvalerate). This plastic is typically produced as a random copolymer; however, using R. eutropha we have developed technology to produce block-copolymer forms of this material that show superior toughness compared to random copolymers of similar PHV fraction.  We produce these materials by a fed-batch biosynthesis in which fructose is used as the primary carbon source and valeric acid is added periodically.  Proper timing of valeric acid additions is achieved by a feedback control loop based on mass spectroscopy data from the biosynthesis off-gas.  Presently we are extending this block-copolymer technology to autotrophic cultivations using CO2 / H2 / O2 mixtures with periodic additions of valeric acid.  Already our data suggests that autotrophic synthesis may permit enhanced control of monomer purity within block domains.  Our goal is to compare the molecular and physical properties of block copolymers produced via autotrophic biosynthesis to those produced via heterotrophic biosynthesis.

Controlled biosynthesis of PHB-co-PHV block copolymers from CO<sub>2</sub> and valeric acid

245th National Meeting (2013)

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Controlled biosynthesis of PHB-co-PHV block copolymers from CO2 and valeric acid

Controlled biosynthesis of PHB-co-PHV block copolymers from CO₂ and valeric acid