Degradation of Metal−EDTA Complexes by Resting Cells of the Bacterial Strain DSM 9103

Abstract

Ethylenediaminetetraacetate (EDTA), an industrially important chelating agent, forms very stable complexes with di- and trivalent metal ions, and in both wastewater and natural waters it is normally present in the metal-associated form. Therefore, the influence of EDTA speciation on its utilization by the EDTA-degrading bacterial strain DSM 9103 was investigated. EDTA-grown cells harvested from the exponential phase of a batch culture were incubated with 1 mM of various EDTA species and the EDTA concentration in the assay was monitored as a function of time. Uncomplexed EDTA as well as complexes with low stability constants (MgEDTA2-, CaEDTA2-, and MnEDTA2-, stability constant < 1016) were found to be readily degraded to completion at a constant rate. For more stable EDTA chelates (i.e. chelates of Co2+, Cu2+, Zn2+, and Pb2+) the data suggest that these complexes were not used directly by the cells but that they had to dissociate prior to degradation. The rate of this dissociation step possibly determined the microbial degradation of these complexes. CdEDTA2- and Fe(III)EDTA- were not degraded within 48 h. In case of CdEDTA2- the toxicity of freed Cd2+ ions most likely prevented a significant degradation of the complex, whereas in case of Fe(III)EDTA- a combination of metal or complex toxicity and the very slow dissociation of the complex might explain the absence of degradation.

EDTA: the chelating agent under environmental scrutiny

“…Thus, in certain cases there is only the ability to degrade metal-chelate complexes of low stability constant, as for example EDTA-Ca (II) and EDTA-Mg (II) complexes 4,45,47 and that in other cases, the exact opposite occurs: the EDTA-Fe(III) complex with a high stability constant is degraded 13,48,49 . Furthermore, from the data available for the intracellular catabolism of EDTA, no generalizing pattern with respect to the influence of metal speciation on degradation can be deduced 50 .…”

The effect of temperature on bacterial degradation of EDTA in pH-auxostat

“…Information is available on only a few EDTA-degrading bacterial strains that have been isolated as pure cultures: Agrobacterium radiobacter ATCC 55002 (Lauff et al 1990), Gram-negative isolates BNC1and ANP 11 (Nö rtemann 1992Kluener et al 1998), and Gram-negative bacterium DSM 9103 belonging to a new genus within the Mesorhizobium/Phyllobacterium group (Witschel et al 1995;Witschel 1999;Weilenmann et al 2004). Degradation of metal-EDTA complexes by several bacterial strains has been reported in recent years (Satroutdinov et al 2000;Eroshin et al 2002;Minkevich et al 2003;Weilenmann et al 2004;Nö rtemann 2005).…”

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides – 1. Microbial Processes and Mechanisms Affecting Bioremediation of Metal Contamination and Influencing Metal Toxicity and Transport

“…A unique aspect of this study was the use of P. putida to treat Nicitrate waste generated by cleaning a bioinorganic ion exchange column previously used to remove Ni. Another industrial chelating agent ethylenediaminetetraacetate (EDTA) also forms very strong complexes with di-and trivalent metals that are degraded by a mixed microbial population ) and by bacterial strain DSM 9103 (Satroutdinov et al 2000). The biodegradation of toxic organotin compounds used as biocides and antifouling agents has also received recent attention (e.g.…”