Fermentation Mechanism Analysis of Reconstituted Tobacco Concentrate by Klebsiella variicola Using Macro-genomics Approaches

In this study, the employment of the aroma-boosting bacterium H8 ( Klebsiella variicola ) under optimal growth conditions significantly improved the content of aroma components in tobacco concentrate and reduced the content of nicotine. We performed a macro-genomic analysis of reconstituted tobacco leaf concentrate fermented by Klebsiella variicola to explain the enhanced aroma compound production and reduced harmful compound production. The results of macro-genomic analysis revealed following facts: (i) Genes related to carbohydrate degradation, amino acid degradation, and lipid degradation accounted for a large proportion of the concentrate microbiome, accounting for 16.1%, 21.8%, and 4.8%, respectively; (ii) Klebsiella variicola is significantly related to the decrease in water-soluble sugar and nicotine; (iii) changes in the contents of 2-acetylpyrrole,β-damascenone, benzyl alcohol, linalool, farnesyl acetone, and phenylethanol are significantly related to the genes abundance of glycoside hydrolases such as GH28, GH42, and GH13; (iv) changes in the contents of dihydrokiwifruit lactone, 2,4-di-t-butylphenol and megastigmatrienones are significantly and positively correlated with the genes abundance changes of Lactobacillus acidophilus , Lactobacillus Faraday and Klebsiella pneumonia; (v) the decrease in the number of aroma-enhancing bacteria during fermentation is due to the autophagy-related protein [ATG5]. This work may be helpful for improving fermentation product quality by regulating the microbial community and gaining insight into the microbial ecosystem.