MICROBIAL-DEGRADATION OF POLY(3-HYDROXYBUTYRATE) AND POLYCAPROLACTONEBY FILAMENTOUS FUNGI

Five strains mere isolated from soil as fungi able to degrade both pol y(3-hydroxybutyrate) (PHB) and polycaprolactone (PCL), and one of the strains, D218, identified as Paecilomyces lilacinus, was selected. In 10 d, D218 degraded PHB almost completely and 10% of the PCL, each at 0.1% in the culture media. Strain D218 excreted PHB and PCL depolymera ses in media containing either PHB, PCL or PHB plus PCL. Both depolyme rase activities were reduced when the medium was supplemented with eit her soluble starch, lactase or glucose. The optimum conditions for PHB depolymerase were pH 6.5 to 7.5 at 50 degrees C, while those far PCL depolymerase were pH 3.5 to 4.5 at 30 degrees C. In the reaction mixtu res used for the enzyme assays, the formation of 3-hydroxybutyrate fro m PHB and epsilon-caprolactone from PCL was confirmed by high performa nce liquid chromatography.