微生物に対する重金属-NTA錯体の毒性

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NTA (nitrilotriacetic acid) degrading bacteria were isolated from activated sludge and the toxic effect of a metal-NTA complex on the utilization of free NTA was examined manometrically by adding different amounts of the metal-NTA complex. Utilization of free NTA was also examined by employing the microorganism previously treated with a metal ion solution.The microorganism utilized the Fe<3+>-NTA complex, but not the Ni<2+>-NTA, Cd<2+>-NTA and Cu<2+>-NTA complexes.In the presence of the Ni<2+>-NTA complex, free NTA was utilized without any interference. No adsorption of Ni<2+> on the microorganism was observed after degradation of NTA had been completed. But degradation of free NTA was strongly inhibited when the microorganism previously treated with Ni<2+> solution was used. The fact that the Ni<2+>-NTA complex did not exhibit a toxic effect on the microorganism could be explained by the non-adsorption of Ni<2+> in the form of a complex on the microorganism.In the presence of the Cd<2+>-NTA or Cu<2+>-NTA complex, the oxygen uptake rate was depressed at the concentration of the metal-NTA complex in the medium increased. But free NTA was quantitatively degraded in both cases. The toxic effect of the Cd<2+>-NTA complex depended upon the amount of Cd<2+> adsorbed on the microorganism. In the case of the Cu<2+>-NTA complex, the degradation rate of free NTA was decreased only to helf of the control, even when the amount of Cu<2+> adsorbed on the microorganism reached 20-60 mg/g-SS. On the contrary, degradation of free NTA was completely inhibited at 1 mg Cu<2+>/g-SS when the microorganism previously treated with a metal ion solution was used. The results indicated that some detoxifying functions were induced in the medium containing free NTA and the Cu<2+>-NTA complex.
1983-09-25

微生物に対する重金属-NTA錯体の毒性

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