Effect of Eu(III) on the degradation of malic acid by and the subsequent production of pyruvic acid

Nankawa, Takuya ; Suzuki, Yoshinori*; Ozaki, Takuo; Onuki, Toshihiko; Francis, A. J.*

We studied the biodegradation of Eu(III)-malic acid complexes by . L-malic acid can be found in the environment and is one of the microbial metabolites which are formed in the TCA cycle. Malic acid was degraded in the absence and in the presence of Eu(III) of 0.05, 0.1, and 0.2 mM. The degradation rate of malic acid increased with decreasing the ratios of Eu(III) to malic acid. These results suggest that the toxicity of Eu(III) can be masked through its complexation with malic acid. The degradation of malic acid was followed by the production of unidentified organic acids which showed higher affinities with Eu(III) than malic acid. Our findings suggest that organic acid with a low chelating ability can influence the environmental behavior of Eu(III) by biologically transformed into the one with a higher chelatingability and through subsequent complexation with Eu(III).