Oxidation unsaturated PHAs

Kurth et al. 2002 Stigers and Tew 2003). One of them involves the oxidation of unsaturated PHAs i.e. poly[(/ )-3-hydroxyoctanoate-co-(/ )-3-hydroxyundecenoate] with KMnO in the presence of NaHCOj (Lee and Park 2000). Although it allowed the transformation of 50% of the olefins into carboxylic functions, this method involves a decrease in the molecular weight of the polymer. 

Figure 7.2 Oxidative carboxylation of unsaturated PHA using KMn04 as an oxidation agent.

P. putida grown with hexanoic acid contained approximately 75, 11, and 10 mol% of 3HHx,3HO, and 3HD units and also small amounts of four unsaturated repeating units. The mechanism for the formation of 3HO unit was investigated by 13C NMR study, which showed that the most of 3HO units found in this PHA were formed by the reaction of hexanoic acid with acetyl-CoA [53]. These results confirmed that P. putida produces 3HA units by fatty acid synthesis pathway, through a -oxidation and chain elongation process. 

The initial drying of currently applied alkyd paints is accomplished by evaporation of solvent (physical drying). Subsequently, the eventual curing of the alkyd paint is completed by the formation of a polymer network, which is mainly formed by chemical crosslinks (oxidative drying) but in some cases also physical interactions between the fatty acid side chains occur, such as crystallization or proton-bridge formation [129]. Efficient network formation is crucial in the formation of dry films with good mechanical properties. Due to the presence of unsaturated units in the investigated LOFA- and TOFA-PHA bin-... 

The cross-linking of P. putida unsaturated mcl-PHAs was performed by adding TiOj pigment powder. Later, pigmented PHA film was cured under either auto-oxidative or photo-oxidative conditions (van der Walle et al. 1999). 

Reiser SE, Mitsky TA, Gruys KJ (2000) Characterization and cloning of an (R)-specific trans-2,3-enoylacyl-CoA hydratase from Rhodospirillum rubrum and use of this enzyme for PHA production in Escherichia coli. Appl Microbiol Biotechnol 53 209-218 Robert J, Marchesini S, Delessert S, Poirier Y (2005) Analysis of the beta-oxidation of tians-unsaturated fatty acid in recombinant Saccharomyces cerevisiae expressing a peroxisomal PHA synthase reveals the involvement of a reductase-dependent pathway. Biochim Biophys Acta 1734 169-177... 

---