METABOLISM OF DIETHYL-ETHER AND COMETABOLISM OF METHYL TERT-BUTYL ETHER BY A FILAMENTOUS FUNGUS, A GRAPHIUM SP

In this study, evidence for two novel metabolic processes catalyzed by a filamentous fungus, Graphium sp. strain ATCC 58400, is presented. F irst, our results indicate that this Graphium sp. can utilize the wide ly used solvent diethyl ether (DEE) as the sole source of carbon and e nergy for growth. The kinetics of biomass accumulation and DEF consump tion closely followed each other, and the molar growth yield on DEE wa s indistinguishable from that with n-butane. n-Butane-grown mycelia al so immediately oxidized DEE without the extracellular accumulation of organic oxidation products. This suggests a common pathway for the oxi dation of both compounds. Acetylene, ethylene, and other unsaturated g aseous hydrocarbons completely inhibited the growth of this Graphium s p. on DEE and DEE oxidation by n-butane-grown mycelia. Second, our res ults indicate that gaseous n-alkane-grown Graphium mycelia can cometab olically degrade the gasoline oxygenate methyl tert-butyl ether (MTBE) . The degradation of MTBE was also completely inhibited by acetylene, ethylene, and other unsaturated hydrocarbons and was strongly influenc ed by n-butane. Two products of MTBE degradation, tert-butyl formate ( TBF) and tert-butyl alcohol (TBA), were detected. The kinetics of prod uct formation suggest that TBF production temporally precedes TBA accu mulation and that TBF is hydrolyzed both biotically and abiotically to yield TBA. Extracellular accumulation of TBA accounted for only a max imum of 25% of the total MTBE consumed. Our results suggest that both DEE oxidation and MTBE oxidation are initiated by cytochrome P-450-cat alyzed reactions which lead to scission of the ether bonds in these co mpounds. Our findings also suggest a potential role for gaseous n-alka ne-oxidizing fungi in the remediation of MTBE contamination.