The impact of natural and synthetic surfactants on bacterial community during hydrocarbon biodegradation

The aim of this study was to analyse the basic mechanisms of the interaction of surfactants anionic rhamnolipids and non-ionic polysorbate-80 on a microbial consortium during the biodegradation of diesel oil under model conditions. The analysed surfactants significantly influenced the metapopulation changes of microorganisms and caused a decrease in metabolic activity; however, they did not decrease the biodiversity of the studied system. Polysorbate-80 was relatively resistant to biological decomposition, whereas rhamnolipids were subjected to biodegradation as well as microbial transformation, as confirmed by the activity of the RhlC gene. Determination of biodegradation kinetics confirmed the positive influence of polysorbate-80 on the degradation efficiency of diesel oil hydrocarbons. The addition of this surfactant in 2-fold and 4-fold critical micelle concentration revealed a positive influence on the total petroleum hydrocarbons biodegradation by 18% and 15% respectively. Rhamnolipids exhibited an inhibiting effect in all fractions, with the exception of n-alkanes. The biodegradation efficiency of total petroleum hydrocarbons was 47% and 40% lower in samples containing biosurfactants in 2-fold and 4-fold critical micelle concentration, compare to that of the control sample. The surfactant-enhanced bioremediation method is a promising alternative to traditional methods; however, the method's efficiency is associated with the proper selection of a surfactant and its concentration and consideration of the occurrence of toxic effects as well as changes in the local soil metapopulation.