No abstract

Anaerobic BTEX biodegradation was tested in batch experiments using an anaerobic sediment as inoculum under Fe(III) and Mn(IV) reducing conditions. All BTEX were degraded under the conditions tested, specially under Mn(IV) reducing conditions, where benzene was degraded at a rate of 0.8 micromol l(-1) d(-1), significantly much faster than Fe(III) reducing conditions. Under Fe(III) reducing conditions, ethylbenzene was the compound that degraded at the faster rate of 0.19 micromol l(-1) d(-1). Mn(IV) reducing conditions are energetically more favourable than Fe(III), therefore, BTEX were more rapidly degraded under Mn(IV) reducing conditions. These results represent the first report of the degradation of benzene with Mn(IV) as the final electron acceptor. Amorphous manganese oxide is a natural widely distributed metal in groundwater, where it can be microbiologically reduced, leading to the degradation of monoaromatic compounds.

Isolated from oil-contaminated soil, Pseudomonas aeruginosa strain MGP-1 was identified by 16S rDNA sequence analysis and phenotypic characterisation. This strain was highly competent in medium and in soils, grew and survived well under adverse conditions. MGP-1 did not produce the pathogenic factor pyocyanin and used paraffin (C 11-40 ) as sole carbon source. It degraded eicosane (C 20 ) more efficiently than other n-alkanes, removing 60% within 16 days. An alkB gene and intermediate metabolites of mono-alcohol and lipid acid corresponding to the oxidised paraffin were detected in the cell-free extracts of MGP-1, indicating that it possessed a mono-terminal oxidation. This is the first report to demonstrate that a Pseudomonas strain is able to degrade paraffin with more than 18 carbon atoms by mono-terminal oxidation. Considering all the results, MGP-1 could be designed as a soil-born, highly competent, long chain n-alkane degrading bacterium with low or perhaps without pathogenicity.