Biodegradation of phenol by a native mixed bacterial culture isolated from crude oil contaminated site Sounak Bera a , Abhijit Sarma Roy a , Kaustubha Mohanty a, b, * a Center for Energy, Indian Institute of Technology Guwahati, Guwahati, 781039, India b Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, 781039, India article info Article history: Received 20 May 2016 Received in revised form 3 April 2017 Accepted 4 April 2017 Available online 7 April 2017 Keywords: Mixed bacterial culture Phenol degradation Inhibition Maximum specific growth rate Dynamic profiles Ortho-cleavage pathway abstract An efficient phenol degrading mixed bacterial culture was isolated from sludge sample collected from one of the refinery located in Assam, India. The mixed culture was found to consist of three bacterial strains. These were identified as Stenotrophomonas acidaminiphila, Brevibacterium sp. and Brucella sp. Batch phenol biodegradation experiments were carried out for a wide range of initial phenol concen- trations after pH and temperature optimization. It was found that the mixed culture was able to degrade a maximum phenol concentration up to 1000 mg L 1 within 96 h while the maximum specific growth rate (m max ) was observed at 100 mg L 1 . The pH and temperature required for optimal phenol degra- dation was 6.5 and 37  C respectively. The mixed culture degrades phenol via ortho-cleavage pathway by formation of an intermediate (cis, cis-muconate) which was detected spectrophotometrically at 260 nm. The experimental data were validated by fitting the growth and substrate utilization curves with their corresponding simulated dynamic profiles obtained by solving Haldane's equation via MATLAB R2015a with m max ¼ 0.155 h 1 and K I ¼ 400 mg L 1 . © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Crude oil drilling and refining activities in North Eastern region of India, particularly Assam, dates back to early part of the nine- teenth century. The natural environment in and around these sites have been continuously exposed to different hydrocarbon compo- nents present in crude oil since those days. The various hydrocar- bons present in crude oil can be classified into aliphatic, aromatic and polycyclic aromatic hydrocarbons (PAHs). Among the different aromatic hydrocarbon contaminants present in crude oil, phenol is of utmost importance due to its recalcitrant nature and widespread prevalence in soil and water ecosystems near the drilling sites and refinery fallouts. This is attributed to its high solubility in water with reports of up to 10,000 mg L 1 (Bajaj et al., 2009) whereas its permissible limit in potable water is 10 3 mg L 1 as recommended by World Health Organization (WHO) (Kumaran and Paruchuri, 1997). Apart from oil drilling sites and refinery fallouts, high con- centration of phenol has also been reported in wastewater dis- charges of other industries like phenol-formaldehyde resin, coal conversion, coking plant, leather, textiles, pharmaceutical etc by various research groups across the world (Huang et al., 2014; Kumaran and Paruchuri, 1997; Pinto et al., 2003; Wang et al., 2014). Phenol is toxic to a host range of beneficial soil and water microbes, aquatic life and plants and has adverse effect on human health even at low concentrations. It has been reported to cause liver and kidney damage, cardiac toxicity, reproductive and devel- opmental toxicity, neurotoxicity, cardiac depression and reduced blood pressure in humans and therefore must be removed from the environment (Huang et al., 2015; Nuhoglu and Yalcin, 2005). Several research groups across the world have reported the degradation of phenol and its derivatives by various physical and chemical methods. However, these methods are quite energy consuming and are not cost effective and also cause secondary pollution (Shourian et al., 2009). On the other hand, biological methods involving potent microorganisms with phenol degrading ability are becoming increasingly popular, as they are inexpensive, eco-friendly and do not cause secondary pollution (Liu et al., 2016). Numerous approaches like immobilization of microbial cells, addition of readily utilizable carbon source as co-substrate or adaptation of microbial cells to high phenol concentrations have been put forward in order to resist the toxicity. However, adapta- tion of microbial cells to high phenol concentration has been * Corresponding author. Center for Energy, Indian Institute of Technology Guwahati, Guwahati, 781039, India. E-mail address: kmohanty@iitg.ernet.in (K. Mohanty). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod http://dx.doi.org/10.1016/j.ibiod.2017.04.002 0964-8305/© 2017 Elsevier Ltd. All rights reserved. International Biodeterioration & Biodegradation 121 (2017) 107e113