Biodegradation of 2-sulfonatofatty acid methyl ester (α-SFMe). 3. Ultimate biodegradation of α-SFMe by activated sludge

For elucidation of the mechanism for the ultimate biodegradation of 2-sulfonatofatty acid methyl ester (α-SFMe), the degradation of sulfosuccinic acid (an analogue to the biodegradation intermediate of α-SFMe, monomethyl α-sulfosuccinate), C14-α-SFMe and 2-14C-labeled C16-α-SFMe, was carried out. The biodegradation was done by measuring BOD, dissolved organic carbon (DOC) and released SO42- using the Japanese MITI test and shake culture method. 14CO2 evolved from radiolabeled α-SFMe was measured by the modified OECD test (14CO2 evolution test). In the MITI test, sulfosuccinic acid was degraded by activated sludge previously acclimatized to α-SFMe but no degradation occurred using unacclimatized sludge. DOC removal continued throughout the shake culture test with C14-α-SFMe, and inorganic sulfate was liberated during the early stage of the test. In the 14CO2 evolution test, radiolabeled α-SFMe showed 77% degradation of the initially added radioactivity after 2 weeks. The present results clearly indicate α-SFMe to be ultimately biodegraded through ω-and β-oxidation, desulfonation (cleavage of C-S linkage) and the oxidation of carbonaceous residues. (author)