Metagenomic insight into the biodegradation of biomass and alkaloids in the aging process of cigar

Abstract

A significant distinction between cigar production and tobacco lies in the necessary aging process, where intricate microbial growth, metabolic activities, enzymatic catalysis, and chemical reactions interact. Despite its crucial role in determining the final quality of cigars, our comprehension of the underlying chemical and biological mechanisms within this process remains insufficient. Biomass and alkaloids are the primary constituents that influence the flavor of cigars. Consequently, investigating the entire aging process could begin by exploring the involvement of microbes and enzymes in their biodegradation. In this study, handmade cigars were aged under different conditions. Metagenomic sequencing was employed to identify the microbes and enzymes responsible for the degradation of biomass and alkaloids derived from tobacco leaves. The results revealed that various environmental factors, including temperature, humidity, duration time, and turning frequency, yielded varying contents of total sugar and alkaloids in the cigars. Significant correlations were observed between microbial communities and starch, reducing sugars, total sugars, and alkaloids. Key species involved in the breakdown of biomass constituents, such as starch (Bacillus pumilus, Pseudomonas sp. 286, and Aspergillus cristatus), reducing sugars and total sugars (Aspergillus cristatus and Nitrolancea hollandica), were identified. Furthermore, Corynespora cassiicola and Pseudomonas fulva were found to potentially contribute to the degradation of alkaloid compounds, specifically nornicotine and neonicotinoid. Our work contributes to a deeper understanding of the microbial roles in the aging of cigars. Moreover, the selection of specific microbial strains or starter cultures can be employed to control and manipulate the aging process, thereby further refining the flavor development in cigar products. Graphical Abstract