Isolation of indigenous Bacillus velezensis from aging tobacco leaves for improving the flavor of flue-cured tobacco

Xiao-Jie Shan¹Lifeng Jin²Feng Li²Shen-Bing Yang¹Xiaojuan Zhang¹Li-Juan Chai¹Jin-Song Gong¹Jin-Song Shi¹Zhen-Ming Lu^1*Zongyu Hu^3*Zheng-Hong Xu^4*

• ¹Jiangnan University, Wuxi, China
• ²Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
• ³China Tobacco Jiangsu Industrial Co., Ltd, Nanjing, China
• ⁴Sichuan University, Chengdu, China

Aging of flue-cured tobacco is a slow microbial fermentation process that usually lasts for 2-3 years, which plays an important role in improving the quality of final products. In this study, re-dried tobacco leaves from seven Chinese regions were subjected to a controlled aging environment for twelve months. The bacterial community succession and volatile compounds dynamics in tobacco leaves throughout aging process were monitored. Spearman's rank correlation analysis revealed that Bacillus was a key genus driving aroma production. By using the pure culture method, strain Bacillus velezensis TB-1 with the best enzyme-producing capacity was screened from high-grade tobacco leaves. Furthermore, Bacillus velezensis TB-1 was applied to low-grade tobacco leaves for solid-state fermentation. GC-MS results showed a significant increase in volatile compounds in fermented tobacco leaves compared to unfermented controls. The contents of 2-methoxy-4-vinylphenol (clove and wood flavors), megastigmatrienone (tobacco and spicy aromas), 2-methyl-hexanoic acid (cream flavor) increased significantly. Sensory evaluation confirmed that fermentation with Bacillus velezensis TB-1 markedly enhanced tobacco leaf flavor quality. This study identified Bacillus velezensis as a core aroma-producing microorganism in tobacco aging, demonstrating its application for fermentation to enhance leaf quality, thus establishing a novel strategy for tobacco improvement.