CELL-RECYCLE FED-BATCH PRODUCTION OF A HIGHLY UNSATURATED POLYHYDROXYALKANOATE FROM 1,3-BUTANEDIOL BY PSEUDOMONAS SP A33

The recently isolated Pseudomonas sp. A33 was investigated for the pro duction of a highly unsaturated polyhydroxyalkanoate (PHA) containing various alkyl and alkenyl pendent groups from 1,3-butanediol in a cell -recycle fed-batch production mode. The monomer composition and degree of unsaturation in PHA were dependent on the environmental conditions . The production temper ature markedly influenced the content, composi tion, and degree of unsaturation of PHA. As the production temperature decreased from 30 to 10 degrees C, the degree of unsaturation and con tent of PHA were increased, while the mole percentage of 3-hydroxybuty rate (3HB) was decreased. These temperature effects on the composition of PHA imply that the production can be used as a control variable fo r the biosynthesis of a highly unsaturated PHA and for the specific re gulation of the composition of PHA. The biosynthetic pathway for a hig hly unsaturated PHA which is based on de novo fatty acid biosynthetic pathway is proposed. For the enhanced production of this functional PH A, a high cell density was achieved by cell-recycle continuous culture at 30 degrees C, and then a large amount of PHA was accumulated at 15 degrees C by fed-batch addition of the feeding solution containing ex cess 1,3-butanediol. The structures of monomer constituents of polymer were confirmed by gas chromatography-mass spectrometric analysis of t rimethylsiyl derivatives of 3-hydroxyalkanoic acids methyl esters.