Biodegradation of oxyethylated fatty alcohols by bacteria Microbacterium strain E19.

The Microbacterium sp. E19 (E19) has been isolated from soil contaminated with crude oil and is a candidate for surfactant enhanced remediation of hydrocarbon polluted soil. Oxyethylated alcohols (OA) are candidates for this process enhancement. The aim of this work was the investigation of biodegradation of a representative oxyethylated fatty alcohol (polydispersal surfactant C12E10(C12E10)) by E19 under static model conditions with the surfactant as a sole source of organic carbon. LC-MS was used for the identification of metabolites and determination of surfactant and metabolite concentrations. Apart from [M+NH4](+) ethoxylate 'fingerprints', [M+2NH4](++) 'fingerprints' (m/z=22) were used for the identification of particular species. Primary biodegradation of C12E10 by E19 is almost complete over 30 days of the test (97 percent). The major metabolites during the initial period of the test are homologs of oxyethylated alcohols ω-carboxylated in the oxyethylene chain and poly(ethylene glycols). 1/3 of the total C12Ex is metabolized along this pathway. Concentration of these metabolites is stable over the subsequent days of the test. Further biodegradation of C12Ex causes an enrichment of the residue with C12Ex homologs having a longer oxyethylene chain. However, intermediates of this process were not identified.

Utilization of Triton X-100 and polyethylene glycols during surfactant-mediated biodegradation of diesel fuel.

The hypothesis regarding preferential biodegradation of surfactants applied for enhancement of microbial hydrocarbons degradation was studied. At first the microbial degradation of sole Triton X-100 by soil isolated hydrocarbon degrading bacterial consortium was confirmed under both full and limited aeration with nitrate as an electron acceptor. Triton X-100 (600 mg/l) was utilized twice as fast for aerobic conditions (t(1/2)=10.3h), compared to anaerobic conditions (t(1/2)=21.8h). HPLC/ESI-MS analysis revealed the preferential biodegradation trends in both components classes of commercial Triton X-100 (alkylphenol ethoxylates) as well as polyethylene glycols. The obtained results suggest that the observed changes in the degree of ethoxylation for polyethylene glycol homologues occurred as a consequence of the 'central fission' mechanism during Triton X-100 biodegradation. Subsequent experiments with Triton X-100 at approx. CMC concentration (150 mg/l) and diesel oil supported our initial hypothesis that the surfactant would become the preferred carbon source even for hydrocarbon degrading bacteria. Regardless of aeration regimes Triton X-100 was utilized within 48-72 h. Efficiency of diesel oil degradation was decreased in the presence of surfactant for aerobic conditions by approx. 25% reaching 60 instead of 80% noted for experiments without surfactant. No surfactant influence was observed for anaerobic conditions.