Biodegradation of diisopropyl ether, ethyl tert-butyl ether, and other fuel oxygenates by Mycolicibacterium sp. strain CH28

Abstract

Growing use of recalcitrant fuel oxygenates like methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and diisopropyl ether (DIPE) poses serious threat to aquatic environments and drinking water sources. Mycolicibacterium sp. strain CH28 was isolated earlier as a potential degrader of DIPE. Optimal culture conditions for strain CH28 were determined to be 32 °C and pH 5.00–6.00. Substrate utilization tests revealed that several n-alkanes, aromatic compounds, short-chain alcohols and acids were metabolized by strain CH28. In resting cell assays, strain CH28 was able to mineralize DIPE with a degradation rate of 1.63 ± 0.03 nmol min−1 mg biomass−1. Complete mineralization of 75 mg l−1 DIPE occurred within 42 hours in microcosm systems using groundwater samples inoculated with strain CH28. 2-propanol, acetone, and acetate were identified as intermediates of DIPE degradation with GC-MS, and a degradation pathway was proposed. Mixed cultures of strain CH28 and Hydrogenophaga sp. strain T4 were able to fully mineralize 200 mg l−1 ETBE in 60 hours. Moreover, strain CH28 could co-oxidize MTBE and TAME in the presence of DIPE as the growth substrate. Our results indicate that strain CH28 holds great potential in the bioremediation of sites contaminated with gasoline ether oxygenates.