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Biodegradation of xenobiotic tertiary alcohols

Activity Code: FP7-PEOPLE-2013-IEF
Project Reference: 624857
Coordinator:Helmholtz-Zentrum für Umweltforschung


Tertiary alcohol groups are not unusual in nature. They can even be moieties of central metabolites, such as citric and mevalonic acid, which are processed by nearly universal metabolic pathways. However, simple tertiary alcohols not possessing additional functional groups are rarely degraded by bacteria or other organisms. These xenobiotic compounds
might be formed during microbial attack of some important groundwater pollutants, such as fuel oxygenate ethers, alkyl phenols, naphthenic acids and related compounds all possessing already a tertiary alcohol group or an aliphatic side chain which could be converted to it in the course of degradation. In most of these cases, the tertiary alcohol is accumulating as dead end metabolite, however Aquincola tertiaricarbonaris L108 and other strains contain mechanisms to degrade the simplest tertiary alcohols: tert-butyl alcohol (TBA) and tert-amyl alcohol (TAA). On principle, the mechanisms involved in the degradation pathways of these mechanisms should be also applicable to larger tertiary alcohols. However, in the TBA- and TAA-degrading bacterial strains PM1 and L108 the enzymes involved in these pathways seem not to be adapted to enable efficient conversion of alcohols with more than 5 carbon atoms (Schuster et al. 2013) and natural evolution towards productive degradation of xenobiotic C6 to C10 tertiary alcohols might be quite difficult. Although a complete pathway for the degradation of larger xenobiotic tertiary alcohols might not exist, partial metabolic sequences at least adapted to monoterpene conversion have been detected in a few bacterial strains. Thus the planned work entails the elucidation of the unknown enzymatic steps related to TBA and TAA degradation, as well as the initiation of a pathway evolution in batch and chemostat cultivation using pure and mixed cultures for specific C6-C10 compounds, analyzing the recombination events and degradation performance of these cultures.