Hindawi Publishing Corporation The Scientific World Journal Volume 2013, Article ID 125385, 15 pages http://dx.doi.org/10.1155/2013/125385 Review Article Current Status on Biochemistry and Molecular Biology of Microbial Degradation of Nicotine Raman Gurusamy and Sakthivel Natarajan Department of Biotechnology, School of Life Sciences, Pondicherry University, Puducherry 605014, India Correspondence should be addressed to Sakthivel Natarajan; [email protected] Received 18 August 2013; Accepted 14 October 2013 Academic Editors: N. Ercal and T. Niu Copyright © 2013 R. Gurusamy and S. Natarajan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Bioremediation is one of the most promising methods to clean up polluted environments using highly efficient potent microbes. Microbes with specific enzymes and biochemical pathways are capable of degrading the tobacco alkaloids including highly toxic heterocyclic compound, nicotine. After the metabolic conversion, these nicotinophilic microbes use nicotine as the sole carbon, nitrogen, and energy source for their growth. Various nicotine degradation pathways such as demethylation pathway in fungi, pyridine pathway in Gram-positive bacteria, pyrrolidine pathway, and variant of pyridine and pyrrolidine pathways in Gram- negative bacteria have been reported. In this review, we discussed the nicotine-degrading pathways of microbes and their enzymes and biotechnological applications of nicotine intermediate metabolites. 1. Introduction of dry weight [7]. The Environmental Protection Agency (EPA) has classified these nonrecyclable powdery tobacco Tobacco (Nicotiana, Solanaceae family) is mainly cultivated wastes as Toxic Release Inventory (TRI) chemicals [8]. When in Brazil, China, Cuba, India, and USA. An annual produc- the concentration of nicotine content exceeds more than tion of 6.7 million tonnes of tobacco has been reported. China 0.05% (w/w), it is designated as “toxic and hazardous” by is the largest tobacco producer (39.6%) followed by India the European Union Regulations (EUR) [7]. These tobacco (8.3%), Brazil (7.0%), and the USA (4.6%) [1]. India is the wastesaredumpedonthegroundwithoutproperstorageand third largest tobacco consumer (275 million) in the world processing [7, 8]. Nicotine dissolves easily in water leading followed by China and USA [2]. It is anticipated that the to the contamination of the ground water [7, 8]. Hence, the tobacco industry would produce 3,00,274 tonnes of nicotine nicotine-contaminated water disturbs the ecological balance wastes every year [3]. Nicotine usually accounts for more of soil [7, 8]. Therefore, it is important to remove nicotine than 90% of the whole plant alkaloid fraction in commercial from tobacco polluted soil and water [7, 8]. tobacco, Nicotiana tabacum [4]. The entire or part of the tobacco leaf was used as raw material for tobacco products such as cigarette, cigars, chewing tobacco, and snuff. 2. Nicotine Intheyear2000,itwasestimatedthat4.9milliondeaths occur due to smoking [5]. By the year 2020, it is also expected Nicotine 3-(1-methyl-2-pyrrolidinyl) pyridine is a hetero- to exceed 9 million deaths annually [5]. Due to the increased cyclic compound with a pyridine and a pyrrolidine ring usage of tobacco products, the industry generated solid moiety. Nicotine is a pale yellow to dark brown liquid with and liquid tobacco wastes containing high concentrations slight fishy odor when warm. It is water-soluble. The chemical of nicotine [6]. The tobacco industries produce tobacco formula of nicotine is C10H14N2. Its molecular weight is ∘ ∘ waste with an average content of nicotine of 18 g per kg 162.234 with melting point –79 Candboilingpoint247C. 2 The Scientific World Journal Nicotine is present up to 2 to 8% of the dry mass of the tobacco [6]. Batham [55] reported that the nitrate content of the soil leaves [9]. increased due to the microbial degradation of nicotine. 2.1. Effect of Nicotine on Human Beings. Nicotine is a haz- 3.1. Optimal Conditions of Nicotine-Degrading Bacteria. ardous compound that causes tobacco related lung cancer Nicotine degradation experiments are carried out with dif- and peripheral arterial disease [10]. Although more than ferent culture media such as distilled water, minimal salt 4000 substances are present in the tobacco cigarette smoke, medium, inorganic salt medium, and basal salt medium nicotine is the major substance [11, 12]. Nicotine has a (BSM). The culture media influence the nicotine degradation blood half-life period of approximately 2 h and causes severe efficiency. Wang et al. [28] reported that 3 g/L nicotine was vascular diseases [11, 12]. Nicotine can cause cancer, gene fully degraded in 5 h when the degradation experiment was mutation, and malformation [13]. An array of toxic nicotine carried out with 0.05 M sodium phosphate buffer (pH 7.0). intermediate metabolites such as N -nitrosonornicotine, 4- However, it took more than 8 h to complete degradation when (methylnitrosamino)-1-(3-pyridyl)-1-butanone, cotinine, and carried out with distilled water. The optimal culture condi- N-nitrosamine causes tobacco lung cancer [14, 15]. Neuro- tions and nicotine degradation efficiency of nicotinophilic bacteria vary from each other. Most of the bacteria grow toxin developmental effects of nicotine can naturally affect a ∘ varietyofcellularprocessessuchasgenerationofoxidative at 30 C, pH range of 6.4 to 7.5, and degrade maximum radicals, apoptosis, and hyperplasia of cell, enhancing gene concentration of nicotine up to 6 g/L [2, 5]. Huang et al. [56] reported that the rate of nicotine degradation efficiency expression to secrete hormones and regulation of enzymatic ∘ ∘ was high at 37 Cwhencomparedto30C. The optimal activity [13, 16, 17]. The lungs rapidly absorb 90% of the conditions and nicotine degradation efficiency of various nicotine that is present in the cigarette smoke inhaled by nicotine-degrading bacteria are presented in Table 1. human beings [18]. Nicotine in the human body can easily pass the biological membranes and blood-brain barrier and increases heart rate, mean arterial blood pressure and mimics 3.2. Effect of Trace Elements, Carbon, and Nitrogen Sources on the venous endothelial dysfunction [15, 19, 20]. Nicotine Degradation. Trace elements and other carbon and nitrogen sources play a significant role in the biodegradation Nicotine is an additive substance that can lead to nicotine of nicotine [26]. The presence of (NH4)2SO4 in the nicotine dependence and addictive behavior in human populations containing medium could decrease the nicotine degradation [43]. Nicotine dependence is complex, multidimensional efficiency [26]. The nicotine degradation rate was increased trait that involves psychological, physiological behavioral, inthepresenceofyeastextract,glucose,andTween80 and social factors [44]. Nicotine, the primary psychoactive in tobacco waste extract (TWE) containing media [57]. ingredient of tobacco, contributes to physical dependence, However, the nicotine degradation rate was dependent on by acting on nicotinic acetylcholine receptors in the central the concentration of yeast extract and Tween 80 in the TWE nervous system and leads to the release of neurotransmitters medium [27]. In contrast, the medium containing glucose (e.g., dopamine and serotonin), which produce reinforcing and (NH4)2SO4 reduced the efficiency of nicotine degrada- effects by activating the mesocorticolimbic dopamine system tion [32]. ZnSO4⋅7H2OandNiCl2⋅6H2Ohadnoinfluenceon [45]. nicotine degradation, whereas Na2MoO4 and CuCl2⋅4H2O inhibited the rate of nicotine degradation [39]. Glucose is an 3. Microbial Degradation of Nicotine important carbon source that promotes bacterial cell growth and improves the rate of nicotine degradation [24, 34, 39]. The Physical and chemical methods are available to degrade nico- concentration of glucose above 10 g/L inhibited the nicotine tineinthetobacco.Thesemethodsareoftentime-consuming, degradation by Pseudomonas sp. ZUTSKD [34]. Raman expensive and involve solvent extraction procedures [46]. et al. [2] reported that 1 g/L dextrose increased nicotine Bioremediation is one of the promising methods to clean up degradation rate. In contrast, glucose is not influenced in the polluted environments using microbes [47–49]. Briski et al. nicotine degradation rate when the experiment was carried [50] reported that aerobic composting is an effective method out in solid-state fermentation process [39, 56]. Jiang et al. to reduce 80% of nicotine and 50% of the volume and mass of [36] reported that the nicotine degradation rate was slow tobacco solid wastes in 16 d. Meher et al. [51]usedatechnique inthepresenceofglucose.Conversely,P. stut z e r i ZCJ could called biomethanation that removed 60% of nicotine, 75.6% not utilize carbon sources such as sucrose and maltose and of chemical oxygen demand, and 80% of biological oxygen nitrogen source, namely, NaNO2,fortheirgrowthwhichin demand from the tobacco wastes. Biological method employs turn inhibits nicotine degradation [39]. a variety of nicotine-degrading bacteria and fungi [41, 46, 51]. These ecofriendly biological methods are extensively used 3.3. Effect of Nicotine-Degrading Bacteria on Tobacco Leaves in wastewater treatment due to its high efficiency and low and Tobacco Wastes. Nicotine-degrading bacteria played an cost. Microbes that degrade nicotine are reported