Abstract
A simple and rapid biodegradation test method (cultivation method) was developed for the screening of chemicals which were hard to be degradable by microorganisms in the natural water. Namely, a water, acetone or dimethyl-sulfoxide solution (0.1 ml) of the test chemicals was added to a mixture of river or sea water (4.9 ml) from unpolluted area and an autoclaved solution (5.0 ml) of 0.2% peptone (added by 3% NaCl for sea water) in a sterile test tube (25×200 mm) with a tight plug. After sealed with film and fixed at angle 30° in a dark box, test tubes were incubated at 30°C and shaked at 120 rpm. At appropriate times during cultivation, the remaining chemicals were determined for obtaining the degradation percentage by growing microorgaisms, which were examined by the measurement of turbidity (OD at 610 nm) of the mixture. This cultivation method gave considerably constant results on many chemicals tested, when degradability was judged from degradation percentage after 3 d-incubation as follows : 100-50% to be easy-, 50-15% to be moderate-, and 15-0% to be hard-of-degradability.
