Screening Of Denitrifying Bacteria And Its Application On TSNA Reduction

Tobacco-specific Nitrosamines (TSNA) is a group of carcinogens which have been found in tobacco, tobacco products, and cigarette smoke only. Tobacco alkaloids, nitrate and nitrite are the precursors of TSNA. There are so many alkaloids in tobacco, and the content of nitrite of tobacco is extremely low, so nitrite is the main factor of TSNA. Using microbes is a new way to reduce TSNA. Denitrification or nitrogen removal has increasingly shown its importance in the treatment of reducing TSNA. Denitrifying bacteria is a kind of bacteria which executes the function of denitrification. The different products become from the intensity of denitrification, so we should isolate the strains with high denitrification.The upper-tobacco leaves were used to be the subject in this study, the denitrifying bacteria reduced TSNA by reducing nitrate & nitrite which were the precursors of TSNA. 25 strains were separated from numbers of flue-cured tobacco samples. Screening out of 25 denitrifying bacteria by the Giltay medium, there were two strains with high denitrification. Nitrate and nitrite were degraded much better, gas was produced earlier and faster by strain T1-2 and T2-2 than other strains, and at last the lower rates of nitrate were 100% and 95.30%, the lower rates of nitrite were 99.00% and 88.78%, respectively. The identification of the two strains by 16S rDN A and the experiment results of physiological and biochemical properties showed that they belongs to Pseudomonas putida, we named them as Pseudomonas putida Tl-2 and Pseudomonasputida T2-2.Our results showed that Pseudomonas putida T1-2 and T2-2 which have been prepared into 108 CUF/mL of suspension could reduce TSNA, the reduction efficiency of T1-2 was NNN 56.48%, NNK-21.36%(P< 0.05); the reduction efficiency of T2-2 was NNN 28.33%, NNK 57.83%(P< 0.05), respectively after 21 days.