The impact of long-term contact of Achromobacter sp. 4(2010) with diesel oil e Changes in biodegradation, surface properties and hexadecane monooxygenase activity Ewa Kaczorek a, * , Karina Sa1ek a , Urszula Guzik b , Beata Dudzi  nska-Bajorek c , Andrzej Olszanowski a a Institute of Chemical Technology and Engineering, Poznan University of Technology, M. Sklodowskiej-Curie 2, 60-965 Pozna n, Poland b University of Silesia, Faculty of Biology and Environment Protection, Department of Biochemistry, Jagiellonska 28, 40-032 Katowice, Poland c State Higher Vocational School, Ks. Kard. Stefana Wyszy nskiego 38, 62-200 Gniezno, Poland article info Article history: Received 14 March 2012 Received in revised form 1 October 2012 Accepted 6 December 2012 Available online 28 December 2012 Keywords: Achromobacter Biodegradation Cell surface hydrophobicity Enzyme activity Fatty acids Zeta potential abstract A bacterial strain was isolated from soil that was contaminated with diesel oil and was used in our experiments. The strain was then phenotypically, biochemically and genetically tested and named as Achromobacter 4(2011). In order to examine the impact of long-term contact with diesel oil of bacterial cells, the strain was stored under different conditions e on standard nutrient agar plates and on agar plates with 50 ml diesel oil as a sole carbon and energy source. The results clearly indicated that longer contact with diesel oil led to changes in both the bacterial surface and biochemical properties, as well as the hexadecane monooxygenase activity. Moreover, the fatty acid profiles also changed, leading to an increased content of saturated fatty acids. In addition, the rates of biodegradation of diesel oil were higher even when supplemented with the surfactants e rhamnolipids and saponins. This work demonstrates that prolonged contact of microorganisms with diesel oil can lead to many changes, not only in biodegradation potential, but also in their surface and genetic properties. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Over the last few years the microbiological degradation of hydrocarbons has been widely described in literature and interest in this method is still growing (Márquez-Rocha et al., 2001; Medina-Bellver et al., 2005). One of the reasons for this trend is that biodegradation is considered to be a very effective and relatively cheap method helpful in reducing water and soil pollution. Petro- leum fuels, crude oil or polycyclic aromatic hydrocarbons in contaminated water and soil are important ecological problems due to their poor water solubility (Bouchez et al., 1995). Limited water solubility of these compounds significantly reduces their bioavailability which, as a consequence, negatively affects biodeg- radation (Megharaj et al., 2011). Thus, many new ideas are being applied to enhance this process and increase it in a significant way. Surface active agents belong to compounds that have recently been discovered to increase biodegradation rates. Thus, the use of these compounds enhances the desorption and solubilization of hydrophobic substances (Kuyukina et al., 2005). Furthermore, surfactants can also improve hydrocarbon utilization due to their emulsifications, as well as through adhesion on microbial cell surfaces (Singh et al., 2007). Special attention is focused on bio- surfactants, (produced by microorganisms), as they are less toxic and easily biodegradable (Costa et al., 2006). Moreover, bio- surfactants can be synthesized from renewable resources, as well as from industrial and domestic wastes. Surfactant adsorption onto bacterial cell surfaces leads to various modifications. The type and the concentration of surface active compounds influences the nature of the cell surface, especially whether hydrophobic or hydrophilic. Zhong et al. (2007) observed that rhamnolipid adsorption plays a role in modifying cell surface hydrophobicity, and the effect of monomer adsorption at low levels of rhamnolipid concentration is more significant than that of micelle adsorption. Increased cell surface hydrophobicity would favor cell adhesion on both hydrophilic and hydrophobic support surfaces (Liu et al., 2004). Cell surface hydrophobicity (CSH) depends on the ratio of hydrophobic and hydrophilic regions on the microbial cell surface (Ron and Rosenberg, 2002). Addition of surfactants exhibits both positive and negative effects when used as additives in a bioreme- diation process. Different research groups reported an improved * Corresponding author. Tel.: þ48 61 665 3688; fax: þ48 61 665 3649. E-mail address: ewa.kaczorek@put.poznan.pl (E. Kaczorek). Contents lists available at SciVerse ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod 0964-8305/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ibiod.2012.12.003 International Biodeterioration & Biodegradation 78 (2013) 7e16