Biosynthesis of polyhydroxyalkanoates from 1,3-propanediol by chromobacterium sp

Abstract

Chromobacterium sp. isolated from a river soil produced blend of a copolyester consisting of 3-hydroxybutanoic acid (3HB) and 3-hydroxypropionic acid (3HP) units and copolyester consisting of the saturated 3-hydroxyalkanoic acid (3HA) units of even carbon number C4 to C14 in addition to two unsaturated 3HA units [3-hydroxy-5-cis-dodecenate (3H5DD) and 3-hydroxy-7-cis-tetradecenoate (3H7TD)] when cultivated on 1,3-propanediol (1,3-PD) as the sole carbon source under nitrogen-free conditions. The copolyesters with 3HP unit have up to 6 mol% 3HP fractions, the number average molecular weight (Mn) with up to 4.4 × 105, the melting temperature (Tm) of 148-158°C and the glass transition temperature (Tg) of 2-4°C. In contrast, the medium-chain-length polyhydroxyalkanoates (PHAMCL) with even carbon number of C6-C14 monomer units have ca. 60 mol% 3-hydroxydecanoate (3HD) fraction as the most predominant component and less than 4 mol% of 3H5DD and 3H7TD fractions as minor. The Mn, Tm and Tg of PHAMCL were ca. 1.2 × 105, 53°C and -45°C, respectively.