Production of Biodegradable Copolyesters by Alcaligenes eutrophus

Abstract

Three different types of biodegradable copolyesters were produced from various carbon substrates in a batch culture of Alcaligenes eutrophus. A random copolymer of 3-hydroxybutyrate and 3-hydroxypropionate, P(3HB-co-3HP), was produced in a nitrogen-free culture solution of 3-hydroxypropionic acid, 1,5-pentanediol, 1,7-heptanediol, or 1,9-nonanedio1. The copolyester of 3-hydroxybutyrate and 4-hydroxybutyrate, P(3HB-co-4HB), was produced from various carbon sources such as 4-h ydroxy but yric acid, Y-but yrolac tone, 1,4-butanediol, 1,6-hexanediol, 1,S-octanediol, 1,10-decanediol, and 1,12-dodecanediol. The copolyester of 3-hydroxybutyrate and 3-hydroxyvalerate, P(3HB-co-3HV), was produced from propionic or pentanoic acid. The pathway of poly(hydroxyalkanoates) , (PHA) metabolism in !.eutrophus has been discussed. The biodegradability of PHA films was studied in the aqueous solution of extracellular PHA depolymerase purified from !.faecalis. The presence of 3HP and 4HB units in the P(3HB) sequence accelerated the rate of enzymatic degradation, whereas the presence of 3HV units retarded the degradation rate of polyester.