BIOSYNTHESIS OF NOVEL COPOLYESTERS CONTAINING 3-HYDROXYPIVALIC ACID BY RHODOCOCCUS RUBER NCIMB-40126 AND RELATED BACTERIA

Rhodococcus ruber and related Gram-positive bacteria synthesized and a ccumulated novel copolyesters containing 3-hydroxypivalic acid as cons tituent if the cells were cultivated in a mineral salts medium contain ing 3-hydroxypivalic acid and glucose as carbon sources. The copolyest ers contributed 0.4-10% of the cellular dry mass, and they contained u p to 78 mol% of 3-hydroxypivalic acid in addition to 3-hydroxybutyric acid and 3-hydroxyvaleric acid; a homopolyester of 3-hydroxypivalic ac id was also synthesized under certain conditions. The presence of 3-hy droxypivalic acid in the accumulated copolyesters was confirmed by nuc lear magnetic resonance spectrometry as well by coupled gas chromatogr aphy/mass spectrometry. This is the first time that the incorporation of 3-hydroxypivalic acid and therefore of a hydroxyalkanoic acid with two methyl group substituents at the alpha-carbon atom in a naturally occurring copolyester is reported. It indicates that 3-hydroxypivalic acid-coenzyme A is accepted by polyhydroxyalkanoic acid synthase as a substrate. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V.