Optimization of copper bioremediation by Stenotrophomonas maltophilia PD2 Arpita Ghosh a, *, Papita Das Saha b a Departmental of Earth and Environmental Study, National Institute of Technology, Durgapur, India b Department of Environmental Science, University of Calcutta, Kolkata, India Introduction Rapid industrialization leads to environmental problem due to heavy metal presence in the effluent [1,2]. Heavy metals naturally occur in the earth crust, which cannot be degraded or destroyed and move through food chains via bioaccumulation [3]. Copper is a transition heavy metal. According to United States Environmental Protection Agency (USEPA), 1978 the most hazardous metals are antimony, arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium and zinc. Copper is an important trace element in plants, animals but it is one of the heavy metal which has some negative impacts on the environment and human in the higher concentration [4–7]. Intake of excessive copper leads to severe mucosal irritation and corrosion, stomach upset and ulcer, wide spread capillary damage, hepatic and renal damage, central nervous system irritation followed by depression, gastrointestinal irritation, and possible necrotic changes in the liver and kidney, Wilson’s disease leading to brain and liver damage [8,9]. Different treatment process exist for removal of Cu(II) from wastewater, including precipitation, ion-exchange, evaporation, oxidation, electroplating and membrane filtration [10–12]. How- ever, application of such technologies has restrained because of technical or economical constraints [13,14]. There is a need of new cost-effective technologies which can reduce the copper from aqueous solution in environmental friendly way [1]. Bioremediation is a popular field of environmental microbiolo- gy, used to degrade toxic organic pollutants, heavy metals using growing cells of bacteria, fungi, algae etc. [15–17]. Micro-organisms have evolved to heavy metal stress via different processes such as transport across cell-membrane, biosorption to cell walls and entrapment in extracellular capsules, oxidation–reduction reactions, precipitation, complexation etc. [18–22]. Micro-organisms have heavy metal uptake capacity from aqueous solution. Heavy metal ions get entrapped in the cellular structure, can also pass into the cell through metabolic cycle, and may biosorbed onto the binding sites of cells. The present study was conducted to optimize the bioremedia- tion of copper by using the novel copper resistant bacteria Stenotrophomonas maltophilia PD2, isolated from soil of polluted wasteland (Dhapa, Kolkata, India). The bacteria is gram-negative, rapidly growing bacteria. Traditional batch studies require optimizing the different process parameters such as pH, initial concentration, agitation, temperature separately [23,24]. But, this approach cannot deter- mine the combined effect of all the process parameters. For scale up studies, conventional batch process is time consuming and to decide the optimum value (which may be unreliable) requires a large number of experiments and thereby increase the overall cost of the process. These problems can be mitigated by optimizing all the process parameters collectively by statistical methods such as response surface methodology (RSM). RSM is a classic combination of Journal of Environmental Chemical Engineering 1 (2013) 159–163 A R T I C L E I N F O Article history: Received 25 December 2012 Received in revised form 18 April 2013 Accepted 19 April 2013 Keywords: Copper(II) resistant bacteria Stenotrophomonas maltophilia PD2 Bioremediation Copper Optimization Response surface methodology A B S T R A C T This study investigates bioremediation of copper using copper-resistant bacteria, Stenotrophomonas maltophilia PD2. Living micro-organism was used to remove copper from aqueous solution. The influence of different parameters on bioremediation by S. maltophilia PD2, such as initial copper concentration and initial pH, contact time of the solution was studied. Response surface methodology (RSM) was applied for the optimization of the process parameters responsible for the bioremediation of copper ion effect and to evaluate the effects and interactions of the process variables. Based on the statistics analysis the optimum condition was found at pH 5.50, copper concentration 50.00 mg L 1 , contact time 26.00 h and the copper removal was 90%. The optimization procedure of bioremediation showed a close interaction between the experimental and simulated values of copper removal. ß 2013 Elsevier Ltd All rights reserved. * Corresponding author. Tel.: +91 8586091124. E-mail addresses: aghoshdstdr21@gmail.com, arpitaghoshdastidar@yahoo.com (A. Ghosh), papitasaha@gmail.com (P.D. Saha). Contents lists available at SciVerse ScienceDirect Journal of Environmental Chemical Engineering jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jec e 2213-3437/$ – see front matter ß 2013 Elsevier Ltd All rights reserved. http://dx.doi.org/10.1016/j.jece.2013.04.012