Bioremediation of nicotine‐contaminated soil and isolation of native <i>Arthrobacter</i> bacterium with high tolerance to nicotine

Abstract Various methods have been reported to reduce the toxicity of nicotine, a major pollutant from the tobacco industry. Biodegradation has attracted increasing attention in recent decades. This study investigated several effects on the biodegradation of nicotine in contaminated soil using the Taguchi experimental design method. The results showed that the reaction time and the addition of sludge biomass to the soil had the greatest effect on increasing the biodegradation efficiency of nicotine‐contaminated soil. Adding molasses as a carbon source had no significant effect on nicotine degradation (increased the degradation efficiency by only 4%), while adding a nitrogen source decreased the biodegradation rate (such that adding yeast extract and urea reduced the bio‐removal amount by about 25% and 10.5%, respectively). The results from the optimization of the process showed that the highest removal amount was achieved in 16 days with 5% by weight of sludge inoculation, without adding additional carbon source and nitrogen (more than 95% removal at initial nicotine concentrations of 2175 mg/kg soil), which indicates the success in nicotine bioremediation. The most potent nicotine‐degrading strain in the treatments was isolated and identified based on its physiological characteristics and 16S rRNA sequence analysis as Arthrobacter sp. (GenBank OR569684). This strain was able to use nicotine as the sole source of carbon, nitrogen, and energy for its growth in liquid mediums and tolerated up to 4000 mg/L nicotine in liquid culture. At this concentration, despite a decrease in bacterial growth, 15.8% destruction occurred within 48 h.