Fate of the Nitrilotriacetic Acid-Fe(III) Complex during Photodegradation and Biodegradation by Rhodococcus rhodochrous

Abstract

Aminopolycarboxylic acids are ubiquitous in natural waters and wastewaters. They have the ability to form very stable water-soluble complexes with many metallic di-or trivalent ions. The iron complex nitrilotriacetic acid-Fe(III) (FeNTA) has been previously shown to increase drastically the rate of photo-and biodegradation of 2-aminobenzothiazole, an organic pollutant, by Rhodococcus rhodochrous. For this paper, the fate of FeNTA was investigated during these degradation processes. First, it was shown, using in situ 1 H nuclear magnetic resonance, that the complex FeNTA was biodegraded by Rhodococcus rhodochrous cells, but the ligand (NTA) alone was not. This result indicates that FeNTA was transported and biotransformed inside the cell. The same products, including iminodiacetic acid, glycine, and formate, were obtained during the photo-and biodegradation processes of FeNTA, likely because they both involve oxidoreduction mechanisms. When the results of the different experiments are compared, the soluble iron, measured by spectrophotometry, was decreasing when microbial cells were present. About 20% of the initial iron was found inside the cells. These results allowed us to propose detailed mechanistic schemes for FeNTA degradation by solar light and by R. rhodochrous.

2-Aminobenzothiazole degradation by free and Ca-alginate immobilized cells of Rhodococcus rhodochrous

“…Indeed 99% of ABT was degraded after 25 h in the combined systems while 37% and 26% of ABT were photo-and biodegraded after 125 h, respectively. In order to understand better which mechanisms were responsible for this improvement of ABT degradation rate, the fate of FeNTA was investigated (Bunescu et al, 2008b). It was shown that FeNTA was transported and biotransformed inside the cell and/or phototransformed in the presence of sunlight (Bunescu et al, 2008b).…”

“…In order to understand better which mechanisms were responsible for this improvement of ABT degradation rate, the fate of FeNTA was investigated (Bunescu et al, 2008b). It was shown that FeNTA was transported and biotransformed inside the cell and/or phototransformed in the presence of sunlight (Bunescu et al, 2008b). The same products were obtained during the photo-and biodegradation processes of FeNTA, including IDA (iminodiacetic acid), glycine and formate, probably because they both involve oxidoreduction mechanisms.…”

In vivo31P and13C NMR investigations ofRhodococcus rhodochrousmetabolism and behaviour during biotransformation processes

“…Light had no direct effect on R. rhodochrous and the photoproducts issued from the transformation of ABT and FeNTA; in particular, • OH radicals issued from FeNTA phototransformation (Abida et al. 2006; Bunescu et al. 2008b) do not present any toxic effect for the energetic metabolism of micro‐organisms.…”

“…2009). Finally, Bunescu et al. (2008b) showed that this strain was also able to transform Fe(III)NTA into Fe(II), IDA (iminodiacetic acid), glycine and formate.…”

“…Also, the activity of light on FeNTA produced • OH radicals that induced the degradation of NTA into IDA, glycine and formate and in parallel the reduction of Fe(III) into Fe(II) (Abida et al. 2006; Bunescu et al. 2008b).…”