Some Characterizations of a Natural Source Bacterium (B-3) Decomposing the Ferric Chelate of EDTA

Abstract

Recently, EDTA has been found at significant concentrations as a contaminant in surface water systems in EU countries, and related regulations and/or directives on its use have been issued. In order to develop a technology to eliminate EDTA-chelates from waste or polluted water, we are investigating microorganisms which decompose the chelates. In the previous paper, it was reported that a microorganism (named B-3) isolated from a soil sample was capable of degrading Fe (III) - EDTA. In this paper, we describe some characterizations of the strain. B-3 showed the highest degradation in a basal medium, at 37°c, for 10 days in a stationary culture, the rate of Fe (III) - EDTA degradation was approximately 90 %. On the other hand, the rate was not superior in a shaking culture compared to a stationary one, even when the cultivation period was prolonged. An attempt to accelerate the degradation rate by adding glucose showed a decrease in pH, and consequently, the rate was declined. With the increasing concentration of nutrients such as peptone and yeast extract, the rate rose rapidly, and was accompanied by pH increase. The optimum pH for the degradation rate was approximately 8.7, according to the experiments with intact cells. The growth of strain B-3 was inhibited by Na salt, Ca and Mg chelates of EDTA, but chelation with Cu, Zn, Pb, Mn and Ni enhanced growth. According to Bergey's manual, characteristics of strain B-3 suggested that the isolate B-3 was a Bacillus sp.