BIODEGRADATION OF ATRAZINE UNDER DENITRIFYING CONDITIONS

Anaerobic biodegradation of atrazine by the bacterial isolate M91-3 wa s characterized with respect to mineralization, metabolite formation, and denitrification. The ability of the isolate to enhance atrazine bi odegradation in anaerobic sediment slurries was also investigated. The organism utilized atrazine as its sole source of carbon and nitrogen under anoxic conditions in fixed-film (glass beads) batch column syste ms. Results of HPLC and TLC radiochromatography suggested that anaerob ic biotransformation of atrazine by microbial isolate M91-3 involved h ydroxyatrazine formation. Ring cleavage was demonstrated by (CO2)-C-14 evolution. Denitrification was confirmed by detection of N-15(2) in h ead-space samples of (KNO3)-N-15-amended anaerobic liquid cultures. In aquatic sediments, mineralization of uniformly ring-labeled [C-14]atr azine occurred in both M91-3-inoculated and uninoculated sediment. Ino culation of sediments with M91-3 did not significantly enhance anaerob ic mineralization of atrazine as compared to uninoculated sediment, wh ich suggests the presence of indigenous organisms capable of anaerobic atrazine biodegradation. Results of this study suggest that the use o f M91-3 in a fixed-film bioreactor may have applications in the anaero bic removal of atrazine and nitrate from aqueous media.