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In the standard test for ready biodegradability THEIC was not degraded. Absence of ready biodegradability is not surprising because mineralization of cyanuric acid and its derivatives is linked to certain microorganisms being specialized for metabolism of the heterocyclic ring system. However, in the scientific literature microbial degradation of derivatives of cyanuric acid and cyanuric acid itself is described.

 

Cyanuric acid also is named s-triazine and is the basic structure of many herbicides. Many studies were performed in the 1980s to determine the microbial degradation of triazine herbicides. In a review article on the “Biodegradation of s-triazine xenobiotics” the knowledge of microbial degradation was summarized (Cook, 1987). Degradation of various s-triazines is characterized by a series of hydrolytic cleavages of various different side chains. Pathways converge to cyanuric acid which is subject to hydrolytic ring cleavage finally leading to carbon dioxide and ammonia. Degradation of triazines and cyanuric acid was shown in aerobic and anaerobic bacteria as well as in fungi.

  

In an aerobic water/sediment study relatively fast primary degradation of THEIC has been shown in two different systems (river and pond), with half-lives for the entire systems of less than 30 days, each. The major metabolite was identified as (3,5-Bis-carboxymethyl-2,4,6-trioxo-[1,3,5]triazinan-1-yl)-acetic acid. Other metabolites appeared at much lower concentrations, and all metabolites were very well water soluble, i.e. no accumulation in sediment. It was demonstrated that THEIC ultimately is mineralised to CO2.

  

Reference:

Cook, A.M. (1987). Biodegradation of s-triazine xenobiotics. FEMS Microbiology Reviews 46:93-116.