Environmental biotechnology Lectures L15.1 Biodegradation of biodiesel/diesel blends in soils: effects on hydrocarbon dissipation and natural microbial communities

It is generally considered that the addition of biodiesel has a positive effect on biodegradation of diesel fuel hydrocarbons. Although the stimulating effect has been widely recognized, the exact mechanisms behind this phenomenon are still not entirely elucidated. While the presence of biodiesel may induce dispersion of diesel fuel hydrocarbons, thereby increasing their overall bioavailability to the degrading microorganisms, its effect on the biodegradation of specific hydrocarbon fractions may differ. This may directly correspond to quantitative and qualitative changes among the microbial community of hydrocarbon degraders involved in the biodegradation processes. In order to investigate this issue we studied the dissipation of specific hydrocarbon fractions during the biodegradation of diesel/biodiesel blends carried out by soil-isolated microbial consortia under different aeration regimes. The community dynamics was assessed by employing real-time PCR and the ddCt method for relative quantification. Interestingly, the obtained results suggested, that FAMEs constituting biodiesel were degraded at the same rate as diesel deriving alkanes. This led to differences in the biodegradation of toxic aromatic fuel constituents and contribute to changes among the growth rates of specific degraders. The evaluation of biodiesel effect was carried out in laboratory conditions as well as during field studies. L15.2