抄録
We studied the effect of Europium, Eu (III), on the degradation of malic acid by the bacterium Pseudomonas fluorescens. Its breakdown depended upon the ratio of Eu (III) - to malic acid-concentrations; the higher the ratio, the less malic acid was degraded. The resulting chemical species of Eu (III), determined by calculations using thermodynamic data, indicated that predominant ones were Eu (Mal) 2- and EuMal+; free Eu (III) constituted less than 1% of the total Eu (III). The degradation of malic acid was independent of Eu (Mal) 2- concentrations. Even though more than 80% of malic acid was present as free malic acid, its degradation was retarded with an increase in the ratio of Eu (III) to malic acid. According to the speciation calculation, the degradation of malic acid was hindered by the presence of EuMal+, as well as by free Eu (III). We also assessed the amount of pyruvic acid generated, which is the major degradation product of malic acid complexed with Eu (III).
