BIOSYNTHESIS OF COPOLYESTERS CONSISTING OF 3-HYDROXYBUTYRIC ACID AND MEDIUM-CHAIN LENGTH 3-HYDROXYALKANOIC ACIDS FROM 1,3-BUTANEDIOL OR FROM 3-HYDROXYBUTYRATE BY PSEUDOMONAS SP A33

Pseudomonas sp. A33 and other isolates of aerobic bacteria accumulated a complex copolyester containing 3-hydroxybutyric acid (3HB) and vari ous medium-chain-length 3-hydroxyalkanoic acids (3HA(MCL)) from 3-hydr oxybutyric acid or from 1,3-butanediol under nitrogen-limitated cultur e conditions. 3HB contributed to 15.1 mol/100 mol of the constituents of the polyester depending on the strain and on the cultivation condit ions. The accumulated polymer was a copolyester of 3HB and 3HA(MCL) ra ther than a blend of poly(3HB) and poly(3HA(MCL)) on the basis of mult iple evidence. 3-Hydroxyhexadecenoic acid and 3-hydroxyhexadecanoic ac id were detected as constituents of polyhydroxyalkanoates, which have hitherto not been described, by C-13 nuclear magnetic resonance or by gas chromatography/mass spectrometric analysis. In total, ten differen t constituents were detected in the polymer synthesized from 1,3-butan ediol by Pseudomonas sp. A33:besides seven saturated (3HB, 3-hydroxyhe xanoate, 3-hydroxyactanoate, 3-hydroxydecanoate, 3-hydroxydodecanoate, 3-hydroxytetradecanoate and 3-hydrohexadecanoate) three unsaturated ( 3-hydroxydodecenoate, 3-hydroxytetradecenoate and 3-hydrohexadecanoate ) hydroxyalkanoic acid constituents occurred. The polyhydroxyalkanoate synthase of Pseudomonas sp. A33 was cloned, and its substrate specifi city was evaluated by heterologous expression in various strains of P. putida, P. oleovorans and Alcaligenes eutuophus.