Selective biodegradation of sorbitan ethoxylated surfactants by soil microorganisms

Abstract

Surfactants have received increasing interest as potential agents for the enhanced remediation of soils and groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs). However, the fate of surfactants with respect to biological transformations and associated changes in their characteristics has not been addressed clearly. Thus, the biodegradation of ethoxylated sorbitan fatty ester non-ionic surfactants, referred to as Tween surfactants, was investigated in this study. The PAH-degrading soil microbes partially utilized the surfactant as a carbon source (26.9-32.7% of initial dose). The characterization of biodegraded surfactants revealed that the partial biodegradation occurred selectively on the hydrophobes of surfactants, resulting in an imbalance of amphiphilic moieties of surfactants. Consequently, the critical micelle concentration values increased by 61.9-88.0% and the micellar solubilization ratio values decreased by 66.5-84.3% after the surfactant biodegradation. These observations supported our conclusion that the partial and selective microbial degradation of surfactants can result in a significant reduction of surface-active and micellar solubilization capacities of surfactants. The findings of this study are expected to provide important implications for the application of surfactant-mediated remediation processes for PAHs. (C) 2013 Elsevier Ltd. All rights reserved.