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Engineering of bacterial poly (3-hydroxyalkanoate) production
Eggink, G.; Huijberts, G.N.M.; de Waard, P. (1993). Engineering of bacterial poly (3-hydroxyalkanoate) production, in: Seventh forum for applied biotechnology, PAND, Gent 30 September - October 1993, abstracts. pp. 17
In: (1993). Seventh forum for applied biotechnology, PAND, Gent 30 September - October 1993, abstracts. RUG: Gent. 150 pp., more

Available in Authors 
    VLIZ: Proceedings [39335]
Document type: Conference paper

Keyword
    Fresh water

Authors  Top 
  • Eggink, G.
  • Huijberts, G.N.M.
  • de Waard, P.

Abstract
    Poly(3-hydroxyalkanoates) (PHAs) of which poly(3-hydroxybutyric acid) (PHB) is the most common, can be accumulated by a large number of bacteria as carbon and energy reserve. PHAs are optically active polymers with properties which vary with their composition. PHB is a highly crystalline thermoplastic whereas PHAs consisting of medium chain length monomers are elastomers with low melting points. These biodegradble and biocompatible polymers have attracted considerable industrial interest since these natural matcrials may find applications in medicine and the packaging industry. The industrial applications of PHAs can be extended by improving the economics of the PHA production process and by increasing the range of polymers which can be produced. We have demonstrated that it is feasible to develop efficient fermentation processes in which long chain fatty acid (LCFAs) derived trom vegetable oils are used as substrates for the production of (novel) PHAs. Fed-batch fermentation studies with Alcaligenes eutrophus showed that high cell mass and PHB production rates can be obtained with LCFAs as the sole source of carbon and energy. In addition it was found that the PHB yield on LCFAs was almost twice the yield obtained with carbohydrates, which currently are used as feedstocks for the commercial production of PHB. PHAs accumulated by Pseudomonas strains consist of medium chain length 3-hydroxy fatty acids (C6-CI4). Our studies on metabolism of PHA in Pseudomonas have shown that PHA synthesis is connected to the general fatty acid metabolic pathways. The monomer composition is determined by the structure of the fatty acid, the fatty acid degradation pathway and the substrate specificity of the PHA polymerase. Therefore a series of novel PHAs can be produced from the available variety of vegetable oil-derived LCFAs, such as saturated, unsaturated and hydroxylated fatty acids. For example during growth on oleic acid and linoleic acid Pseudomonas putida accumulates copolymers consisting of 5 different monomers, including 10-20% (poly)unsaturated 3-hydroxy fatty acids. The presence of unsaturations in the alkyl side chain of the monomers allows further chemical modification thereby extending the potential applications of these copolymers. At present genetic and physiological studies on fatty acid metabolism in P. putida are in progress. Detailed knowledge of PHA metabolism is a first step to pathway manipulation for controlled synthesis of biodegradable polyesters with specific chemical, physical and mechanical properties.

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