Production of chiral R-3-hydroxyalkanoic acids and R-3-hydroxyalkanoic acid methylesters via hydrolytic degradation of polyhydroxyalkanoate synthesized by pseudomonads.

A novel and efficient method for the production of enantiomericaly pure R-3-hydroxyalkanoic acids and R-3-hydroxyalkanoic acid methylesters was developed. The described method is based on hydrolysis of poly(hydroxyalkanoate) copolymers synthesized by Pseudomonas putida. The polymer was isolated via solvent recovery and hydrolyzed by acid methanolysis. The obtained 3-hydroxyalkanoic acid methylester mixture was distilled into several fractions with an overall yield of 96.6% (w/w). Gas chromatography-mass spectrometry analysis of the fractions showed that 3-hydroxyhexanoic-, 3-hydroxyoctanoic-, 3 hydroxydecanoic-, and 3-hydroxydodecanoic acid methylesters were enriched to purities exceeding 96 mol%, with distillation yields of 99.9, 99.8, 88.4, and 56.8% (w/w), respectively. Subsequent saponification of the purified methylester fractions yielded the corresponding 3-hydroxyalkanoic acids, which were recovered up to 92.8% (w/w). Chiral gas chromatography analysis confirmed that both 3-hydroxyoctanoic acid and 3-hydroxyoctanoic acid methylester are present in the R-form at a very high enantiomeric excess (>99.9%).