ENHANCED BIOSYNTHESIS OF P(3HB-3HV) AND P(3HB-4HB) BY AMPLIFICATION OF THE CLONED PHB BIOSYNTHESIS GENES IN ALCALIGENES-EUTROPHUS

The biosynthesis of P(3HB-3HV) and P(3HB-4HB) was carried out using tr ansformants of Alcaligenes eutrophus harboring the cloned phbCAB, phbA B, and phbC genes. The molar fractions and yields of 3HV and 4HB incre ased significantly by enhancing enzymes related to PHB biosynthesis co mpared to the parent strain. Especially, PHB synthase was the most cri tical enzyme that regulated monomer compositions of P(3HB-3HV) and P(3 HB-4HB) in the transformant. Even at the lower propionate or 4-hydroxy butyrate concentrations, the high molar fractions of 3HV or 4HB could be accumulated. The enforcement of PHB biosynthetic enzymes through th e transformation of corresponding genes was identified to be an excell ent method for modification of monomer composition of copolymer of A. eutrophus.