Cometabolism of methyl tertiary butyl ether and gaseous n-alkanes by Pseudomonas mendocina KR-1 grown on C5 to C8 n-alkanes

Pseudomonas mendocina KR-1 grew well on toluene, n-alkanes (C(5) to C(8)), and 1degrees alcohols (C(2) to C.) but not on other aromatics, gaseous n-alkanes (C(1) to C(4)), isoalkanes (C(4) to C(6)), 2degrees alcohols (C(3) to C(8)) methyl tertiary butyl ether (MTBE), or tertiary butyl alcohol (TBA). Cells grown under carbon-limited conditions on n-alkanes in the presence of MTBE (42 mumol) oxidized up to 94% of the added MTBE to TBA. Less than 3% of the added MTBE was oxidized to TBA when cells were grown on either 1degrees alcohols, toluene, or dextrose in the presence of MTBE. Concentrated n-pentane-grown cells oxidized MTBE to TBA without a lag phase and without generating tertiary butyl formate (TBF) as an intermediate. Neither TBF nor TBA was consumed by n-pentane-grown cells, while formaldehyde, the expected C(1) product of MTBE dealkylation, was rapidly consumed. Similar K(s) values for MTBE were observed for cells grown on C(5) to C(8) n-alkanes (12.95 +/- 2.04 mM), suggesting that the same enzyme oxidizes MTBE in cells grown on each n-alkane. All growth-supporting n-alkanes (C(5) to C(8)) inhibited MTBE oxidation by resting n-pentane-grown cells. Propane (K(i) = 53 muM) and n-butane (K(i) = 16 muM) also inhibited MTBE oxidation, and both gases were also consumed by cells during growth on n-pentane. Cultures grown on C(5) to C(8) n-alkanes also exhibited up to twofold-higher levels of growth in the presence of propane or n-butane, whereas no growth stimulation was observed with methane, ethane, MTBE, TBA, or formaldehyde. The results are discussed in terms of their impacts on our understanding of MTBE biodegradation and cometabolism.