EFFICIENT HYDROLYSIS OF POLYHYDROXYALKANOATES BY PSEUDOMONAS-STUTZERI YM1414 ISOLATED FROM LAKE WATER

Ten species of independent Gram-negative bacteria capable of degrading polyhydroxyalkanoates (PHA) were isolated from the fresh water of Lake Biwa. The hydrophobicities of PHA depolymerases from the isolates were determined from the partition coefficient between hydrophobic gels and buffers. The hydrophobicities of the enzymes from bacteria isolated from aqueous environments were relatively higher than those from other environments. The PHA depolymerase was purified to electrophoretic homogeneity from the culture medium of one isolate, Pseudomonas stutzeri YM1414, by a preparative-scale isoelectric focusing in the Rotofor and a gel filtration, and its molecular weight was determined as 48 000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The optimum activity of the depolymerase on the degradation of poly[(R)-3-hydroxybutyrate] (P[(R)3HB]) was observed at pH9.5 and 55 degrees C. The rate of enzymic degradation of P[(R)3HB] him was about twice as high as that due to the enzymes from other bacteria such as Alcaligenes faecalis, Pseudomonas pickettii, Comamonas testosteroni, and Pseudomonas lemoignei.