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

Abstract

The aging process is the final step in cigar production and plays a vital role in the quality. There are complex microbial growth and metabolism, enzymatic catalysis, and chemical reactions in this process. Among them, microorganisms function as a bridge between organic and inorganic contents. At present, we do not yet have sufficient knowledge of the evolution of microorganisms in the aging process of cigars. Neither are we clear about the mechanisms by which environmental conditions may impact the quality of cigars through the interaction of microorganisms and chemical substances. In this study, we used a metagenomics sequence-guided strategy to identify the microbes and enzymes involved in the degradation of key compounds, biomass and alkaloids, under different environmental conditions. The results showed that different environmental factors including temperature, humidity, aging cycle, and turning frequency resulted varied contents of total sugar, and alkaloids in cigars. Microbial communities showed significant correlations with starch, reducing sugars, total sugars and alkaloids. Vital species in the catabolism of starch (Bacillus pumilus, Pseudomonas sp. 286 and Aspergillus cristatus), reducing sugars and total sugars (Aspergillus cristatus and Nitrolancea hollandica) were identified. Corynespora cassiicola and Pseudomonas fulva were proposed to contribute to the degradation of nornicotine and neonicotinoid. Our work should deepen the understanding of microbial roles in cigar aging and provide a new viewpoint for applying specific microbial consortia to modulate the degradation of biomass and alkaloids in cigar leaves.