IDENTIFICATION OF 4-HYDROXYHEXANOIC ACID AS A NEW CONSTITUENT OF BIOSYNTHETIC POLYHYDROXYALKANOIC ACIDS FROM BACTERIA

Various aerobic Gram-negative bacteria were analysed for utilizing 4-h ydroxyhexanoic acid (4HHx) as a carbon source for growth and for synth esis of polyhydroxyalkanoic acids (PHA). Although many wild types grew on 4HHx, only recombinant strains of the PHA-negative mutants Pseudom onas putida GPp104 and Alcaligenes eutrophus PHB(-)4, which harboured plasmid pHP1014::E156 with the PHA-biosynthesis genes of Thiocapsa pfe nnigii, incorporated 4HHx up to a molar fraction of 47 of 1.4%, respec tively, into PHA if the cells were cultivated in the presence of 4HHx as sole carbon source and under nitrogen starvation. A terpolyester co nsisting of 3-hydroxybutyric acid (3HB), 3-hydroxyhexanoic acid (3HHx) and 4HHx was synthesized, as revealed by gas chromatographic analysis of the accumulated polyester and as confirmed by nuclear magnetic res onance spectroscopic analysis of the isolated polyester. 4HHx was also detected in PHA accumulated by Rhodococcus ruber if 4HHx was used as a carbon source. However, it occurred at a molar fraction of maximally 1.3 mol% only beside 3HB, 3-hydroxyvaleric acid and 3HHx.