Identification And Metabolic Pathway Of A Nicotine-degrading Bacterium5-28

Nicotine is one of key factors related to tobacco quality and a toxic substance in environment, in fact, nicotine is the major harmful ingredient in wastewater and tobacco waste. In addition, nicotine is water-soluble, so it can permeate into groundwater and contaminate water. Along with the increase of consciousness of healthness and environment protection, people show increasingly concerns on the harm from nicotine. It is of profound significance for protecting people’s health and natural balance to efficiently control the contents of nicotine in cigarette products and environment.In this study, a nicotine-degrading bacterium strain was isolated from tobacco plantation soils and identified. Its optimal conditions for nicotine degradation were determined. Furthermore, parts of its metabolites in nicotine degradation were identified by HPLC and LC-MS analysis. The main results were as follows.(1) Screening, isolation and identification of the nicotine-degrading bacterium strain. One bacterium which can degrade nicotine steadily was isolated from seven soil samples by using nicotine as the sole source of carbon and nitrogen. According to the16S rRNA analysis, the strain5-28belongs to Sinorhizobium sp..(2) Optimal conditions for nicotine degradation of strain5-28. The growth of strain5-28during nicotine degradation was affected by many factors. Strain5-28can tolerate2.5g/L nicotine, and the optimal conditions for nicotine degradation were1.5g/L nicotine, pH4.0and25℃.(3) Ability of the resting cells of strain5-28in nicotine degradation. The nicotine inducible type and non-inducible type resting cells prepared from strain5-28can degrade nicotine efficiently. And the nicotine inducible type resting cells degraded nicotine more efficient. It degraded1g/L nicotine completely in6h. While the nicotine no-inducible type resting cells degraded only80%nicotine in the same time.(4) Identification of nicotine metabolites of strain5-28. The metabolites of nicotine degradation from different times were detected by HPLC and LC-MS, and two compounds,6-Hydroxynicotine and6-Hydroxy-N-methylmyosmine, were identified. In addition, no apparent pigment was observed in the degradation of nicotine by strain5-28, implying that the metabolic pathway of nicotine in strain5-28may be similar to Arthrobacter nicotinovorans and Agrobacterium tumefaciens S33, but their metabolites in the late stage were different.In summary, we have isolated and identified a bacterium stain Sinorhizobium sp.5-28 with a stable ability of nicotine-degradation for the first time. It can grow by using nicotine as the sole source of carbon and nitrogen, revealing potential value of application in cigarette processing and environmental remediation of nicotine pollution.