In pollutants when dealing with vast volume of

In the past few years, waste effluents and recalcitrant compounds have become an important environmental concern (Semple et al., 2001). Among the diverse types of contaminants, polycyclic aromatic hydrocarbon (PAHs) given top priority by US-EPA and European Union (Wenzl et al., 2006; Yan et al., 2004). PAHs belongs to a diverse group of environmental pollutant and more than 100 species of PAHs are ubiquitously distributed in the environment and due to its carcinogenic, teratogenic properties (Wills et al., 2008) many of them are harmful to human health (Kim, 2016). Moreover, increased global uses of fossils fuels and indiscriminate anthropogenic activities causes abandoned release of PAHs in the environments (Wang et al., 2011; Williams et al., 2008). Furthermore, in a recent report by the Toxic Release Inventory (TRI), petroleum refinery industries are listed in top ten major sources, releasing toxic chemicals into the environment (Riad et al., 2017). The physico-chemical properties of PAHs makes them less soluble in water and the high affinity to the fatty tissues, makes them spread via bio-magnification (Diggs et al., 2011). The age-old techniques like landfilling, incineration, gasification and plasma gasification etc. are extremely expensive and do not work with all types of pollutants when dealing with vast volume of contaminates (Azubuike et al., 2016). A convenient alternative, bioremediation, and several others variations like phytoremediation, rhizoremediation, nano-remediation are environment-friendly, cost-effective and rapidly evolving with time (Yim et al., 2007). Indeed, this a new era of bioremediation techniques. The characteristics of PAHs have been well studied and the genetic aspects of PAHs degradation have been documented previously (Yim et al., 2007). Naphthalene, the simplest form of the polycyclic aromatic hydrocarbon is most volatile in the nature and its methylated derivatives are also considered as notorious compounds for ground water contamination (Yu et al., 2006). In addition, naphthalene has been classified as class-c carcinogen by US-EPA and considered in indoor air quality guidelines by World Health Organization (WHO), (Jennings, 2012). Moreover, biodegradation of naphthalene by indigenous soil bacteria (ISB) is abundant in the literature by several bacterial species including Novosphingobium sp,  Pseudomonas sp., Burkholderia sp., and Rhodococcus sp. (Segura et al., 2017; Vaidya et al., 2017). In addition, bio-augmentation and bio-stimulation are two techniques used to boost up bioremediation by applying nutrient in a controlled way (Tyagi et al., 2011). In this study we have isolated Pseudomonas putida strain KD9 from petroleum refinery waste. The biodegradation potential of KD9 have been characterized by HPLC and GCMS with the secondary carbon supplements such as glucose, starch, sucrose, and L-arginine. The primary enzyme for naphthalene biodegradation, naphthalene 1,2-dioxygenase (nahAc) had been sequenced and its relative expression with secondary carbon supplements were also assessed during biofilm mode of growth of the KD9. Best of our knowledge there is no such study conducted to identify potential secondary carbon supplement for PAHs biodegradation. 

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