APPLIED MICROBIAL AND CELL PHYSIOLOGY Effect of surfactants on fluoranthene degradation by Pseudomonas alcaligenes PA-10 Anne Marie Hickey & Linda Gordon & Alan D. W. Dobson & Catherine T. Kelly & Evelyn M. Doyle Received: 18 August 2006 / Revised: 10 October 2006 / Accepted: 10 October 2006 / Published online: 15 November 2006 # Springer-Verlag 2006 Abstract Two surfactants, Tween 80 and JBR, were investigated for their effect on fluoranthene degradation by a Pseudomonad. Both surfactants enhanced fluoranthene degradation by Pseudomonas alcaligenes PA-10 in shake flask culture. This bacterium was capable of utilising the synthetic surfactant and the biosurfactant as growth substrates and the critical micelle concentration of neither compound inhibited bacterial growth. The biosurfactant JBR significantly increased polycyclic aromatic hydrocar- bon (PAH) desorption from soil. Inoculation of fluoran- thene-contaminated soil microcosms with P. alcaligenes PA-10 resulted in the removal of significant amounts (45± 5%) of the PAH after 28 days compared to an uninoculated control. Addition of the biosurfactant increased the initial rate of fluoranthene degradation in the inoculated micro- cosm. The presence of a lower molecular weight PAH, phenanthrene, had a similar effect on the rate of fluoran- thene removal. Keywords PAHs . Fluoranthene . Biodegradation . Surfactants Introduction Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants that are listed as priority pollutants by the US EPA (Keith and Telliard 1979). The hydrophobic nature of these compounds has resulted in their persistence and bioaccumulation in soil and sediment environments (Kanaly and Harayama 2000; Meador et al. 1995). A range of bacteria, fungi and algae capable of PAH degradation have been isolated and have been the subject of a number of reviews (Cerniglia 1997; Juhasz and Naidu 2000; Smith 1990; Smith et al. 1997; Wilson and Jones 1993). Failure of soil-bound PAHs to partition back into the aqueous phase can severely limit microbial degradation, and it is generally accepted that low bioavailability is one of the major factors affecting the persistence of these compounds in soil (Banat et al. 2000; Mueller et al. 1996). Application of surfactants has been suggested as a possible way to increase bioavailability, and thus, biodeg- radation of these compounds. Although surfactants have been reported to facilitate biodegradation in some instances (Herman et al. 1997; Sobisch et al. 2000), they have been shown to retard or have no effect on contaminant removal in other cases (Deschênes et al. 1996; Laha and Luthy 1991, 1992). The failure of surfactant addition to promote biodegradation has been attributed to surfactant use as a preferential growth substrate by degrading microorganisms (Tiehm 1994; Tiehm et al. 1997), surfactant toxicity (Aronstein et al. 1991; Willumsen et al. 1998), substrate toxicity due to an increase in bioavailability brought about by surfactant solubilisation (Bramwell and Laha 2000) and a reduction in contaminant bioavailability due to its uptake into the surfactant micelle (Doong and Lei 2003; Laha and Luthy 1991). There is growing interest in the use of biosurfactants for environmental applications, as synthetic Appl Microbiol Biotechnol (2007) 74:851–856 DOI 10.1007/s00253-006-0719-5 A. M. Hickey : C. T. Kelly : E. M. Doyle (*) School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Republic of Ireland e-mail: evelyn.doyle@ucd.ie L. Gordon : A. D. W. Dobson Department of Microbiology, National University of Ireland, University College Cork, Cork, Republic of Ireland