Degradation of phytosterols in tobacco extract by bacteria to produce low benzo[a]pyrene reconstituted tobacco
Pyrolysis of phytosterols during tobacco combustion is closely related to the yield of PAHs, such as the carcinogen benzo[a]pyrene. There are five types of phytosterols in tobacco, accounting for 0.2-0.5 % by weight. Most of the phytosterols are hardly removed during the production of tobacco products, which could cause a potential risk to smokers. Here, we try to reduce the contents of phytosterols in reconstituted tobacco by adding phytosterol degradation bacteria in the tobacco extract (TE). Therefore, the benzo[a]pyrene content was reduced in the mainstream smoke during pyrolysis of reconstituted tobacco. A novel bacteria Paenibacillus sp. isolated from the surface of tobacco leaf was used in this study. Paenibacillus sp. cells were cultivated under the optimal conditions (37 °C, pH 7.0) and then collected and added to the TE directly during the production of reconstituted tobacco for phytosterols degradation. Phytosterol degradation in TE was demonstrated by high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). Then, the contents of benzo[a]pyrene in reconstituted tobacco mainstream smoke was determined by gas chromatography/mass spectrometry (GC–MS/MS). Under optimal conditions (37 °C, pH 7.0, with the exponential-phase cells), the total degradation ratio of phytosterols reached 39.5 % in TE, including 44.2 % of stigmasterol (45.2 µg/ml to 25.2 µg/ml), 38.1 % of β-sitosterol (184.5 µg/ml to 114.2 µg/ml), 35.7 % of campesterol (4.82 µg/ml to 3.1 µg/ml) and 52.0 % of cholesterol (5.21 µg/ml to 2.5 µg/ml). Further analysis showed that the final contents of phytosterols in reconstituted tobacco were also reduced by 34.1 % (252.6 µg/g to 166.5 µg/g) compared with the control experiment (without adding bacteria in TE). The delivery of benzo[a]pyrene in mainstream smoke was reduced from 4.22 ng/cig to 2.88 ng/cig. These results indicated that the novel Paenibacillus sp. can potentially be used to produce low benzo[a]pyrene content reconstituted tobacco.