Methyl tert-butyl ether (MTBE) degradation by a microbial consortium

The widespread use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in a large number of cases of groundwater contamination. Bior emediation is often proposed as the most promising alternative after treatm ent. However, MTBE biodegradation appears to be quite different from the bi odegradation of usual gasoline contaminants such as benzene, toluene, ethyl benzene and xylene (BTEX). In the present paper, the characteristics of a consortium degrading MTBE in liquid cultures are presented and discussed. M TBE degradation rate was fast and followed zero order kinetics when added a t 100 mg l(-1). The residual MTBE concentration in batch degradation experi ments ranged from below the detection limit (1 mug l(-1)) to 50 mug l(-1). The specific activity of the consortium ranged from 7 to 52 mg(MTBE) g(dw)( -1) h(-1) (i.e. 19-141 mg(COD) g(dw)(-1) h(-1)). Radioisotope experiments s howed that 79% of the carbon-MTBE was converted to carbon-carbon dioxide. T he consortium was also capable of degrading a variety of hydrocarbons, incl uding tert-butyl alcohol (TBA), tert-amyl methyl ether (TAME) and gasoline constituents such as benzene, toluene, ethylbenzene and xylene (BTEX). The consortium was also characterized by a very slow growth rate (0.1 d(-1)), a low overall biomass yield (0-11 g(dw) g(MTBE)(-1); i.e. 0.040 g(dw) g(COD) (-1)), a high affinity for MTBE and a low affinity for oxygen, which may be a reason for the slow or absence of MTBE biodegradation in situ. Still, th e results presented here show promising perspectives for engineering the in situ bioremediation of MTBE.