Isolation And Identification Of The Nicotine-degradation Bacteria And Its Application

Nicotine, constituting over 95% of total alkaloids in tobacco, is a significant factor of evaluation for tobacco and cigarettes. However, nicotine is also an important environmental pollutant. Therefore, it is of significance to take effective measures for decreasing nicotine contents of cigarettes and wastes.Herein, we report the isolation and characterization of a Pseudomonas strain (designated as CS3) according to the morphological, physiochemical characteristics, and sequence analysis of 16S rDNA, capable of utilizing nicotine as sole source of carbon and nitrogen from a tobacco field soil.The characteristics of nicotine degradation by strain CS3 were investigated. The result showed that the optimal conditions for nicotine degradation were: 5 % inoculum, temperature at 37℃and pH value at 7.0. The degradation of Nicotine by CS3 achieved 98.6% within 24 h when the initial concentration was 1000 mg/L. The strain could endure 4000 mg/L nicotine in liquid culture, adapt to a wide pH range from 6.0 to 10.0 and possess excellent stability and persistence in repetitive degradation operations. These observations suggest that it has great potentials for bioremediation of nicotine-contaminated environments.Under the optimal conditions, the kinetic model of cell growth was obtained and well described by the equationμ= 0.792 / (1 + 511.51/ C S + CS/1169.11). The optimal kinetic parameters calibrated from experimental data in terms of Equation wereμmax=0.792 h-1, K S=511.51 mg/L and K IS=1169.11 mg/L.HPLC and GC/MS analyses revealed the equation three intermediates of nicotine degradation by strain CS3, i.e., 3-(3, 4-dihydro-2H-pyrrol-5-yl) pyridine, 1-methyl-5-(pyridin-3-yl) pyrrolidin-2-ol, and continine, suggesting unique nicotine catabolism pathways in strain CS3. Based on the comparison between the structure of nicotine and the detected intermediates, the nicotine degradation in strain CS3 is postulated to be initiated by direct demethylation to form 3-(3,4-dihydro-2H-pyrrol-5-yl) pyridine (demethylation pathway, similar to that in plants and fungi), or by hydroxylation at position 2 of pyrrolidine ring to form 1-methyl-5-(pyridin-3-yl) pyrrolidin-2-ol, which is then oxidized to continine.CS3 exhibited pronounced degradation efficiency in soils. This property makes it a good environment-friendly candidate for applications in the bioremediation process of nicotine-contaminated soils.