Biodegradation of [S,S], [R,R] and mixed stereoisomers of ethylene diamine disuccinic acid (EDDS), a transition metal chelator.
An in-depth biodegradation test program was executed on the hexadentate ligand Ethylene Diamine Di Succinate (EDDS). The EDDS structure contains two chiral carbon atoms, and has three stereoisomers ([R,R], [R,S]/[S,R], [S,S]). Our research has focused on the isomer mixture (i.e. 25%[S,S]; 25%[R,R]; 50%[S,R]/[R,S], as produced from the reaction of ethylene diamine with maleic anhydride) and on the single [S,S]- and [R,R]-isomers. Biodegradation screening of the 14C-labelled EDDS isomer mixture in a Batch Activated Sludge (BAS) test with various inocula revealed incomplete mineralization, up to ca. 65% after 28 days. N-(2-aminoethyl) aspartic acid (AEAA), probably the d-isomer, was identified as the major portion of the 14C-material remaining in solution. Further testing revealed that the [S,S]-isomer is rapidly and completely mineralized in all test systems. By contrast, [R,R]-EDDS remained undegraded in a Sturm (OECD 301B) test, but was very slowly biotransformed into the recalcitrant metabolite AEAA in a BAS test. The [S,R]/[R,S] form undergoes biotransformation to AEAA in both high and low biomass systems. In a sewage treatment simulation test (OECD 303) the steady state DOC removal of mixture-EDDS in a CAS test was limited to 25-35%, even after extensive pre-acclimation, while the [S,S]-isomer achieved nearly complete removal (96%). This study illustrates the importance stereospecificity may have on the biodegradation and metabolite formation of a chemical. A biodegradation scheme for the different EDDS stereoisomers is proposed.
Schowanek
D
D
Procter & Gamble European Technical Center, Strombeek-Bever, Belgium.
Feijtel
T C
TC
Perkins
C M
CM
Hartman
F A
FA
Federle
T W
TW
Larson
R J
RJ
D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D001673:Biodegradation, Environmental; D018533:Biomass; D002614:Chelating Agents / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005029:Ethylenediamines / Q000737:chemistry / Q000378:metabolism*; D007553:Isotope Labeling; D009682:Magnetic Resonance Spectroscopy; D012722:Sewage; D013237:Stereoisomerism; D013386:Succinates / Q000737:chemistry / Q000378:metabolism*; D018505:Waste Management
D002614:Chelating Agents; D005029:Ethylenediamines; C107222:N-(2-aminoethyl)aspartic acid; D012722:Sewage; D013386:Succinates; C041447:N,N'-ethylenediamine disuccinic acid; D001224:Aspartic Acid