ENZYMATIC DEGRADATION OF POLY(HYDROXYALKANOATES) BY A MARINE BACTERIUM

A bacterium capable of degrading poly(hydroxyalkanoates) (PHA) was isolated from sea water and identified as Comamonas testosteroni. The strain C. testosteroni excreted an extracellular PHA depolymerase and grew on poly(3-hydroxybutyrate) [P(3HB)] as a sole carbon source. The PHA depolymerase was purified from the culture medium to electrophoretic homogeneity by hydrophobic column chromatography, and its molecular weight was determined to be about 50000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The optimum activity of the depolymerase in degrading P(3HB) was observed in the alkaline region between pH9.5 and 10.0. The enzymatic degradation of microbial copolyesters was studied by the weight loss (erosion) of solution-cast films of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate). The PHA depolymerase had a very high hydrophobicity to adhere to the surface of the polyesters.