Biodegradation of nicotine by a newly isolated Agrobacterium sp. strain S33

To isolate and characterize bacteria capable of degrading nicotine from the rhizospheric soil of a tobacco plant and to use them to degrade the nicotine in tobacco solid waste.

A bacterium, strain S33, was newly isolated from the rhizospheric soil of a tobacco plant, and identified as Agrobacterium sp. based on morphology, physiological tests, Biolog MicroLog3 4.20 system and 16S rRNA gene sequence. Using nicotine as the sole source of carbon and nitrogen in the medium, it grew optimally with 1.0 g l(-1) of nicotine at 30 degrees C and pH 7.0, and nicotine was completely degraded within 6 h. The resting cells prepared from the glucose-ammonium medium or LB medium could not degrade nicotine within 10 h, while those prepared from the nicotine medium could completely degrade 3 g l(-1) of nicotine in 1.5 h at a maximal rate of 1.23 g nicotine h(-1) g(-1) dry cell. Using the medium containing nicotine, glucose and ammonium simultaneously to cultivate strain S33, the resting cells could degrade 98.87% of nicotine in tobacco solid waste with the concentration as 30 mg nicotine g(-1) dry weight tobacco solid waste within 7 h at a maximal rate of 0.46 g nicotine h(-1) g(-1) dry cell.

This is the first report that Agrobacterium sp. has the ability to degrade nicotine. Agrobacterium sp. S33 could use nicotine as the sole source of carbon and nitrogen. The use of resting cells of the strain S33 prepared from the nicotine-glucose-ammonium medium was an effective method to degrade nicotine and detoxify tobacco solid waste.

Nicotine in tobacco wastes is both toxic and harmful to human health and the environment. This study showed that Agrobacterium sp. S33 may be suitable for the disposal of tobacco wastes and reducing the nicotine content in tobacco leaves.