Usefulness of soil p-nitrophenyl acetate esterase activity as a tool to monitor biodegradation of polybutylene succinate (PBS) in cultivated soil

Degradation behaviors of polybutylene succinate (PBS) and p-nitrophenyl acetate (pNPA) esterase activity in soil were monitored for six months in the experimental field located at Fujieda in Japan. The PBS used in this experiment was an aliphatic polyester which was under trial product as a new thermoplastic material (Mn=7.0x10.(4) This PBS was prepared through direct dehydration polycondensation without diisocyanate as coupling agent for increasing molecular weight. Cellulose filter paper was used as a control for the degradation test. This PBS strips (50 mm x 30 mm, thickness of 0.3 mm) mixed with field moist soil sample which had been sieved (<2 mm mesh) were packed in bags made of glass-fiber filter papers. The bags were buried in the surface soil layer (0-10 cm) of experimental field. Weight of PBS strip was decreased by approximately 20% in six months. Scanning electron microscopy (SEM) photographs showed that the surface of the PBS strip was gradually corroded in soil. During PBS degradation, pNPA esterase activity in the peripheral soil was higher than that of the soil without PBS addition. Actinomycetous PBS degrader was isolated from peripheral soil of degrading PBS strip using PBS agar plate. The isolate exhibited pNPA esterase activity which was competitively inhibited by PBS particles. These results suggested that pNPA esterase activity of soil is an useful indicator of PBS biodegradation in soil.