Microbial toxicity assessment and biodegradation of triclopyr using Arthrobacter globiformis and Pseudomonas pictorum

Abstract

Triclopyr (3,5,6-trichloro-2-pyridinyloxyacetic acid) was investigated for biodegradation using Arthrobacter and Pseudomonas sp. bacteria. No evidence of the proposed major metabolite, 3,5,6-trichloro-2-pyridinol was found in sole carbon source or enriched growth medium experiments. Triclopyr, and various salts of triclopyr were also tested for toxicity using a modified INT reduction method which relied upon the enzymes from dead, lysed cells in the mature culture. The EC50 values for Arthrobacter and Pseudomonas sp. bacteria were found to be 46 and 470 ppm respectively for triclopyr. The proposed major metabolite 3,5,6-trichloro-2-pyridinol was found to be considerably more toxic to both bacteria than triclopyr. The EC50 results were compared to those for 2,4-D and picloram using the same method. Analysis of triclopyr by gas chromatography and nuclear magnetic resonance was investigated in order to simultaneously quantitate the herbicide and its proposed major metabolite. Synthesis of triclopyr using various starting materials was also investigated to achieve an efficient laboratory scale synthesis. Different synthetic routes will be useful for further studies which may make use of radiolabeled triclopyr since selective inclusion of the radiolabeled depends on the synthesis used.