Quimico

World J Microbiol Biotechnol (2010) 26:329–335 DOI 10.1007/s11274-009-0180-6

ORIGINAL PAPER

Biodegradation of chrysene by the bacterial strains isolated from oily sludge
Monika Dhote Æ Asha Juwarkar Æ Anil Kumar Æ G. S. Kanade Æ Tapan Chakrabarti

Received: 25 June 2009 / Accepted: 9 September 2009 / Published online: 19 September 2009 Ó Springer Science+Business Media B.V. 2009Abstract The biodegradation studies were conducted to test the ability of the bacterial strains (Chry2 and Chry3) isolated from the oily sludge obtained from Gujarat refinery, India, for utilization of chrysene in the liquid medium. Biodegradation of the compound was confirmed using gas chromatography and the percent degradation was calculated to be 15.0 and 17% by Chry2 and Chry3, respectively. Thebiodegradation results were supported by increase in viable cell count and dry biomass, in the presence of chrysene as the sole carbon source. Both the cultures produced biosurfactant which was indicated by the reduction in surface tension of the growth medium. Presence of catechol 2, 3-dioxygenase gene in Chry3 indicated its potential for degradation of PAHs through meta cleavage degradation pathway.Both the strains were found to possess catechol 1,2-dioxygenase and catechol 2,3-dioxygenase enzyme activities. Based on morphological and biochemical tests, the cultures were tentatively identified as Bacillus sp. (Chry2) and Pseudomonas sp. (Chry3). Keywords Biodegradation Á Chrysene Á Biosurfactant Á Dioxygenase enzyme

Introduction Petroleum refineries generate a huge amount of oily sludgeduring storage of crude oil in tanks and refining process. The oily sludge is a complex mixture of saturated and cyclo alkanes, aromatics, heavy metals, with asphaltene as the dominant compound. The solvent extractable aromatic fraction of oil sludge is a group of 16 polycyclic aromatic hydrocarbons (PAHs) which are toxic pollutants of priority as per USEPA (Keith and Telliard 1979). These toxiccompounds are released in to the environment due to improper disposal of oil sludge which accumulates in the surrounding of the industry, thereby polluting the environment. Although some of the PAHs are recalcitrant in nature but microbial communities hold a considerable potential to remediate such oil-contaminated environments (Ramsay et al. 2000; Tam et al. 2002; Hadibarata et al. 2009) throughvarious enzymes mediated catabolic processes. Most aromatic hydrocarbon biodegradation pathways invariably form catechol as intermediate that is typically cleaved by ortho- or meta cleavage dioxygenases (Meyer et al. 1999; Mesarch et al. 2000; Cerniglia 1984; Smith 1990). However, high hydrophobicity and hence low solubility of PAH compounds reduce their bioavailability which ultimately results intheir poor biodegradation in the natural environment (Cerniglia 1993). Increasing the solubility of these compounds using surface active agents as biosurfactants produced by certain bacteria offers an ecofriendly solution for bioremediation of PAH prospective and employment of (Johnsen and Karlson 2004; Cameotra and Bollag 2003; Deziel et al. 1996). Chrysene is one of such high molecular weight PAHsconsisting of 4 fused-benzene rings with solubility 0.006 mg/l. It is highly recalcitrant under normal conditions due to its structural complexity and strong molecular

M. Dhote Á A. Juwarkar (&) Á G. S. Kanade Á T. Chakrabarti Environmental Biotechnology Division, National Environmental Engineering Research Institute (NEERI), Nehru Marg, Nagpur 440020, India e-mail: aa_juwarkar@neeri.res.in M.Dhote Á A. Kumar School of Biotechnology, Devi Ahilya University, Khandwa Road, Indore 452001, India e-mail: ak_sbt@yahoo.com

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World J Microbiol Biotechnol (2010) 26:329–335

bonds. High environmental concerns due to its carcinogenic and mutagenic nature (Smith et al. 1989; Nwanna et al. 2006) compel us to look for innovative methodologies for its biodegradation. Chrysene...