Production And Characterization Of New Medium Chain Length Polyhydroxyalkanoates

Polyhydroxyalkanoates, abbreviated as PHA, is a family of intracellularpolyesters synthesized by many bacteria. The piezoelectricity, biocompatibility andbiodegradability of PHA have offered these polymers many promising applications invarious areas. In addition, chiral monomers of PHA are highly interesting forapplication as intermediates for synthesis of pharmaceutics and pesticides.This study mainly focused on biosynthesis and characterization of new type ofmedium chain length PHA.Knockout mutant Pseudomonas putida KT2442 termed Pseudomonas putidaKTOY06 (P. putida KTOY06) which 3-ketoacyl-CoA thiolase (fadA) and3-hydroxyacyl-CoA dehydrogenase (fadB) in P. putida KT2442 was knocked out,respectively, was used to biosynthesized new mcl-PHA by tetradecanoate, fadA andfadB were catalyzed the last two steps inβ-oxidation pathway in P. putida KT2442. Inthis study, mcl-PHA which HTD monomer ranged from 31mo1% to 49mo1% wereobtained, the monomer composition is dependent on different cultivation conditions.Non-mcl-PHA HTD was observed because of higher HTD content in lyophilizedcells than HTD content in the extracted mcl-PHA, indicating the possible existence ofnon-mcl-PHA HTD as intracellular substances. NMR was studied after thenon-mcl-PHA HTD being extracted showed that the free and/or oligo HTD werealmost oligo HTD, and average molecular weights were estimated by Gel PermeationChromatography (GPC).The average molecular weight, thermal properties, mechanism properties,thermal stability and other properties of these high HTD content mcl-PHA wereanalyzed in this study. The mcl-PHA containing high HTD monomer contents wasfound to have both higher crystallinity and improved tensile strength compared withthat of typical mcl-PHA...