Effective degradation of organic pollutants in aqueous media by microbial strains isolated from soil of a contaminated industrial site

Background: Bioremediation is a low-cost technology, whose efficacy is often enhanced with preliminary mild physical–chemical remediation methods. A further advantage of bioremediation resides in its eco-compatibility and, thus, sustainability. Two autochthonous microbial strains, Methylobacterium populi VP2 and Aspergillus sydowii VP4, were isolated from a soil of a highly contaminated industrial site and used to degrade the aqueous extract of contaminants (AEC) obtained from the same polluted soil. Results: The AEC incubation with both strains produced a significant removal of most organic pollutants, although the degradation capacity decreased with increasing AEC concentration in the minimal selective liquid medium (MSML) of the experiments. At 30 % of AEC, M. populi VP2 determined the removal of most pollutants and the appearance of new products due to oxidation and enzymatic degradation. Incubation of A. sydowii VP4 at the same AEC concentration in MSML removed the same pollutants but also the derived degradation products. Our results showed that the strains isolated from a highly contaminated soil maintained the capacity to use organic contaminants as metabolic carbon in aqueous extracts from the same soil. The greater biodegradation efficiency of the fungal strain in comparison to M. populi VP2 may be caused by a modification of the A. sydowii VP4 cell surface that increases cell permeability to hydrophobic compounds and thus enhances the extent of pollutants degradation. Conclusions: This work indicates that two specific strains, M. populi VP2 and A. sydowii VP4, isolated from the soil of a highly contaminated site are not only useful in the treatment of leaching polluted waters but may also be used in bioaugmentation practices during remediation of contaminated soils.