Microbial community and metabolic function analysis of cigar tobacco leaves during fermentation

Cigar tobacco leaves (CTLs) contain abundant bacteria and fungi that are vital to leaf quality during fermentation. In this study, artificial fermentation was used for the fermentation of CTLs since it was more controllable and efficient than natural aging. The bacterial and fungal community structure and composition in unfermented and fermented CTLs were determined to understand the effects of microbes on the characteristics of CTLs during artificial fermentation. The relationship between the chemical contents and alterations in the microbial composition was evaluated, and the functions of bacteria and fungi in fermented CTLs were predicted to determine the possible metabolic pathways. After artificial fermentation, the bacterial and fungal community structure significantly changed in CTLs. The total nitrate and nicotine contents were most readily affected by the bacterial and fungal communities, respectively. FAPROTAX software predictions of the bacterial community revealed increases in functions related to compound transformation after fermentation. FUNGuild predictions of the fungal community revealed an increase in the content of saprotrophic fungi after fermentation. These data provide information regarding the artificial fermentation mechanism of CTLs and will inform safety and quality improvements.

Automated summary

This study investigated the effects of microbes on the characteristics of cigar tobacco leaves (CTLs) during artificial fermentation, revealing significant changes in bacterial and fungal community structure and composition in fermented CTLs. The total nitrate and nicotine contents in CTLs were directly affected by the bacterial and fungal communities after fermentation. Predictions of bacterial functional changes and an increase in saprotrophic fungi content in fermented CTLs were also observed. These findings provide valuable insights into the artificial fermentation mechanism of CTLs and its potential impact on safety and quality improvements.