ENGINEERING THE COMPOSITION OF CO-POLYESTERS SYNTHESIZED BY ALCALIGENES-EUTROPHUS

Co-polyesters of 3-hydroxybutyrate and 3-hydroxyvalerate were produced by Alcaligenes eutrophus H16 from valeric or propionic acid under bot h air and knallgas (80:20 H-2:O-2) atmospheres. Selectivity for poly-3 -hydroxyvalerate (PHV) synthesis over poly-3-hydroxybutyrate (PHB) is favored under hydrogen, presumably because high NADH levels under knal lgas inhibit breakdown of PHV monomer precursors to PHB precursors. Sw itching the atmosphere from knallgas to air and back again to knallgas was shown to change the bacterial metabolism back and forth, producin g different monomer precursors for polymer synthesis. The experiments suggest that this metabolic switching may be used to produce polyhydro xyalkanoates with blocky regions within the polymer or polymer granule s with shells of different polymer composition. (C) 1998 Elsevier Scie nce Limited. All rights reserved.