Identification and degradation characteristics of a nicotine-degrading strain Pu17

The level of nicotine content is an important index of tobacco quality control, and how to reduce the content of nicotine in these tobacco leaves is a practical problem. Microbial degradation of nicotine has the advantages of low cost and good ecological compatibility, but there are few reports on the application of nicotine-degrading bacteria in tobacco production. Based on this, this study isolated and purified a strain from tobacco growing field in Hunan Province. Morphology combined with scanning electron microscopy showed that the strain was rod-shaped bacteria, 16S rRNA sequencing was Paenarthrobacter ureafaciens, named Pu17. Enzyme activity assay showed that Pu17 produced protease, but not amylase, cellulase and β-glucosidase. The degradation characteristics of Pu17 were analyzed by ELISA. The optimum growth rate of Pu17 was 2.0 g/L, the optimum growth temperature was 30℃, and the optimum growth pH was 6. The Slogistic model was used to compare the growth of Pu17 in pure nicotinic medium and LB medium with a nicotine concentration of 2 g/L. The lag time in growth nicotinic medium with 0.1%, 1.0% and 2.0% inoculations was 27.91, 12.16 and 11.68 h, respectively. In LB with a nicotine concentration of 2.0 g/L, the growth delays corresponding to 1.0% and 2.0% inoculations were 2.11 and 0.36 h, respectively. High performance liquid chromatography (HPLC) analysis showed that Pu17 could grow with nicotine as the only carbon and nitrogen source, and cultured in the medium with nicotine concentration of 2.0 g/L for 48 h, the nicotine that Pu17 degraded reached 92.75%. In LB liquid medium with nicotine concentration of 2.0 g/L, the maximum degradation rate reached 90.57% at 60 h. The nicotine content in tobacco leaves was degraded significantly by spraying Pu17 in the field, and Pu17 reached a significant difference level at 24 h after spraying (P < 0.0001). The difference was also significant at 60 h (P=0.0175). In this study, P. ureafaciens was screened to degrade tobacco nicotine and its degradation characteristics were defined, which provided microbial resources for the degradation of tobacco nicotine and provided a new idea for environmental protection.