Study on dynamic changes and correlations of microbial diversity, key enzyme activity and conventional components in tobacco leaves during the aging process

This study focuses on the aging process of strong-flavor flue-cured tobacco leaves (SCTL) and light-flavor flue-cured tobacco leaves (FCTL), and explores the effects of microbial metabolism and enzyme action on tobacco leaf components and quality during this process. It employs methods including high-throughput sequencing, functional prediction of microbial communities via the PICRUSt2/MetaCyc database, dynamic analysis of conventional components and enzyme activities, and redundancy analysis. The results showed that under the same aging duration, the microbial community diversity structures of tobacco leaves with different quality grades were similar, and a total of 21 species of differential bacteria and 9 species of differential fungi were screened out; During the aging process, the contents of starch and total phenols in tobacco leaves decreased significantly, reducing sugars and total sugars showed a fluctuating trend, while total nitrogen and total plant alkaloids had no significant changes. Among them, the starch content in SCTL was higher than that in FCTL, while the contents of total phenols, reducing sugars and total sugars in SCTL were lower than those in FCTL; the contents of total nitrogen and total plant alkaloids were comparable between the two types of tobacco leaves. Additionally, the contents of reducing sugars, total sugars and starch in both types of tobacco leaves were positively correlated with tobacco leaf grade, while the contents of total phenols and total nitrogen were negatively correlated with tobacco leaf grade; The enzyme activities in the two types of tobacco leaves showed fluctuating changes during aging, and redundancy analysis (RDA) identified significant correlations between microbial taxa, enzyme activities and tobacco leaf compounds. This study provides a basis for microbial strain selection and precision fermentation strategies in tobacco aging.