Limitations in Mtbe Biodegradation

Abstract

The Me tert-Bu ether (MTBE) metabolic pathway was partially elucidated in Mycobacterium austroafricanum IFP 2012 by identifying degrdn. intermediates. Several enzymic activities were specifically induced during growth on MTBE. Among those required for the first steps of MTBE degrdn. to tert-Bu alc. (TBA), the same monooxygenase was responsible for oxidn. of MTBE and TBA, with a low affinity for TBA (Km = 1.1 mM). An esterase was involved in the hydrolysis of tert-Bu formate (TBF). The slowness of MTBE degrdn. by M. austroafricanum IFP 2012 resulted from complex interactions, esp. the neg. effect of TBF formed during MTBE oxidn. on the MTBE/TBA moonoxygenase and the absence of TBA oxidn. in the presence of residual MTBE. Moreover, concerning the downstream steps of MTBE metab., Co2+ ions were required to degrade 2-hydroxyisobutyric acid (HIBA) formed by TBA oxidn. as shown by the low growth yield on HIBA in the absence of Co.