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The production and characterization of bacterially produced poly(beta-hydroxyalkanoates), PHAs
Abstract
The metabolic flexibility of various bacteria in producing unusual poly($\beta$-hydroxyalkanoates), PHAs, was studied. A major effort was undertaken to produce bacterial polyesters other than the usual poly($\beta$-hydroxybutyrate-co-$\beta$-hydroxyvalerate), P(HB-co-HV), by growing bacteria on non-natural carbon substrates, in the form of carboxylic acids or lactones. The three bacteria studies were: Rhodospirillum rubrum, Alcaligenes eutrophus, and Rhodobacter sphaeroides. All three bacteria favored the metabolization of shorter, carboxylic acids of seven carbons or less. R. rubrum was shown to be the most versatile bacterium in being able to incorporate unusual repeat units into the polymer. The bacterium produced PHAs containing longer, pendent groups of n-propyl and n-butyl. The bacterium was able to incorporate pendent groups of olefin groups, hydroxy groups, and possible chloro groups into the PHAs. R. rubrum also showed the ability in incorporating longer, main-chain, carbon spacers into the polyester backbone. The bacterium seemed to incorporate $\alpha$-substituted methyl groups into the PHAs when grown on $\alpha$-substituted acids. A. eutrophus showed the production of PHAs containing units of varying, main-chain, carbon spacers. However, this was the only flexibility which A. eutrophus showed in PHA production other than the production of usual P(HB-co-HV) copolymers. Rb. sphaeroides, like A. eutrophus, only showed flexibility in producing PHAs having units of longer, main-chain, carbon spacers. Both A. eutrophus and Rb. sphaeroides were able to biosynthesize large amounts of deuterated PHB. The growth and polymer production of both R. rubrum and A. eutrophus were effected by the use of a cofeed when fed in combination with another acid to the bacteria. The cofeed caused the bacteria to incorporate various acids into polymer as unusual polymer units, which were not incorporated when the bacteria was grown on the unusual carbon source alone. Most of the bacterial polymers analyzed were determined to be physical mixtures of various copolymers. Aerobic growth of R. rubrum generally increased the amount of intracellular polymer accumulated by the bacterium, when compared to the polymer yields obtained by R. rubrum grown anaerobically in the light.
Subject Area
Polymer chemistry|Biochemistry
Recommended Citation
Ulmer, Herbert Wilhelm, "The production and characterization of bacterially produced poly(beta-hydroxyalkanoates), PHAs" (1992). Doctoral Dissertations Available from Proquest. AAI9219511.
https://scholarworks.umass.edu/dissertations/AAI9219511