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Applied and Environmental Microbiology, March 2007, p. 1783-1791, Vol. 73, No. 6
0099-2240/07/$08.00+0     doi:10.1128/AEM.01899-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Carbon Conversion Efficiency and Limits of Productive Bacterial Degradation of Methyl tert-Butyl Ether and Related Compounds

Roland H. Müller,^* Thore Rohwerder, and Hauke Harms

UFZ, Helmholtz Centre for Environmental Research, Department of Environmental Microbiology, Permoserstr. 15, D-04318 Leipzig, Germany

Received 9 August 2006/ Accepted 3 January 2007

The utilization of the fuel oxygenate methyl tert-butyl ether (MTBE) and related compounds by microorganisms was investigated in a mainly theoretical study based on the Y_ATP concept. Experiments were conducted to derive realistic maintenance coefficients and K_s values needed to calculate substrate fluxes available for biomass production. Aerobic substrate conversion and biomass synthesis were calculated for different putative pathways. The results suggest that MTBE is an effective heterotrophic substrate that can sustain growth yields of up to 0.87 g g^–1, which contradicts previous calculation results (N. Fortin et al., Environ. Microbiol. 3:407-416, 2001). Sufficient energy equivalents were generated in several of the potential assimilatory routes to incorporate carbon into biomass without the necessity to dissimilate additional substrate, efficient energy transduction provided. However, when a growth-related kinetic model was included, the limits of productive degradation became obvious. Depending on the maintenance coefficient m_s and its associated biomass decay term b, growth-associated carbon conversion became strongly dependent on substrate fluxes. Due to slow degradation kinetics, the calculations predicted relatively high threshold concentrations, S_min, below which growth would not further be supported. S_min strongly depended on the maximum growth rate µ_max, and b and was directly correlated with the half maximum rate-associated substrate concentration K_s, meaning that any effect impacting this parameter would also change S_min. The primary metabolic step, catalyzing the cleavage of the ether bond in MTBE, is likely to control the substrate flux in various strains. In addition, deficits in oxygen as an external factor and in reduction equivalents as a cellular variable in this reaction should further increase K_s and S_min for MTBE.

Published ahead of print on 12 January 2007.

Present address: Aquatic Biotechnology, Biofilm Centre, University Duisburg-Essen, Geibelstr. 41, D-47057 Duisburg, Germany.

This article has been cited by other articles:

• Muller, R. H., Rohwerder, T., Harms, H. (2008). Degradation of fuel oxygenates and their main intermediates by Aquincola tertiaricarbonis L108. Microbiology 154: 1414-1421 [Abstract] [Full Text]