Optimization of profenofos degradation by a novel bacterial consortium PBAC using response surface methodology Hina Jabeen a, b , Samina Iqbal a, b, * , Samina Anwar a , Rebecca E. Parales c a Soil and Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), PO Box 577, Jhang Road, Faisalabad 38000, Pakistan b Pakistan Institute of Engineering and Applied Sciences (PIEAS), PO Nilore, Islamabad, Pakistan c Department of Microbiology and Molecular Genetics, College of Biological Sciences, University of California, Davis, Davis, CA, USA article info Article history: Received 19 September 2014 Received in revised form 15 February 2015 Accepted 18 February 2015 Available online Keywords: Profenofos Biodegradation Bacterial consortium Response surface methodology 4-Bromo-2-chlorophenol abstract Profenofos (PFF), an organophosphate (OP) insecticide, has been widely used for last two decades to control insect pests. Extensive use of this toxic pesticide is leading to serious environmental conse- quences which impose development of methods to reduce the environmental burden of PFF using an environmental friendly and cost effective approach. In this study, a PFF degrading bacterial consortium PBAC consisting of Achromobacter xylosoxidans, Pseudomonas aeruginosa, Bacillus sp. and Citrobacter koseri, was developed. Interestingly, compared to pure isolates, the consortium degraded PFF more efficiently. Following a 2 3 full factorial central composite design based on Response Surface Methodology (RSM), different culture conditions were optimized for PFF degradation. The optimal pH, temperature and inoculum size were found to be 6.83, 34.59  C (~35  C) and 0.59 g L 1 respectively to achieve maximal degradation of PFF (93.39%). Analysis of the degradation products revealed that 4-bromo-2- chlorophenol (BCP) was the major metabolite of PFF which was further metabolized to simpler prod- ucts. Importantly, PBAC was capable of degrading a wide range of OP and other pesticides which renders it a useful tool for remediation of soil with a cocktail of contaminants. © 2015 Elsevier Ltd. All rights reserved. Introduction Profenofos (PFF) [(O-4-bromo-2-chlorophenyl)-O-ethyl-S-pro- pylphophorothioate] is a broad spectrum, non-systemic and foliar organophosphate (OP) insecticide. It was developed for controlling wide range of insect pests that were resistant to chlorpyrifos and other OPs (Worthing, 1979). One reason for the extensive use of PFF is a deceptive view of its short half-life in soil, however, it has been recognized as highly persistent and toxic pesticide even at low concentrations (Zhao et al., 2008). According to World Health Organization (WHO) this compound has been classified as a moderately hazardous (Toxicity class II) pesticide (Abass et al., 2007; Malghani et al., 2009b). It inhibits the acetylcholinesterase enzyme (Costa, 2006). Many reports reveal the genotoxicity of PFF to non-target aquatic and terrestrial organisms such as fish & earthworms (Kavitha and Venkateswara Rao, 2009; Liu et al., 2012). The environmental concerns of profenofos and its metabolites have compelled us to pay attention towards the biodegradation of this pesticide. Microbial degradation using naturally occurring bacterial strains is considered to be a potential remedy for removing pesticide residues from contaminated sites whereby the toxic pollutants are converted to potentially innocuous products (Watanabe et al., 1996). More recently, bacterial consortia obtained from highly contaminated sites have been found very efficient in removing the contaminants at high concentrations (Krishna and Philip, 2008; Lakshmi et al., 2009). Regarding the microbial degradation of PFF, limited number of bacterial strains have been reported to date which include Pseudomonas putida & Burkholderia gladioli (Malghani et al., 2009b), Pseudomonas aeruginosa (Malghani et al., 2009a) and Bacillus subtilis (Salunkhe et al., 2013). These strains were found to hydrolyze PFF to a toxic product, 4- bromo-2-chlorophenol (BCP) which is also a specific and sensitive exposure biomarker for PFF (Dadson et al., 2013). Further degra- dation of BCP by these isolates has not been reported. * Corresponding author. Soil and Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), PO Box 577, Jhang Road, Faisalabad 38000, Pakistan. Tel.: þ92 41 2651475; fax: þ92 41 2651472. E-mail address: siqbaleb@gmail.com (S. Iqbal). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod http://dx.doi.org/10.1016/j.ibiod.2015.02.022 0964-8305/© 2015 Elsevier Ltd. All rights reserved. International Biodeterioration & Biodegradation 100 (2015) 89e97