Key nutrients in cigar tobacco leaf fermentation revealed by metagenomics analyses for aroma production optimizations

Xi Chen¹Jun Yu²Tengfei Guo¹Xiong Chen¹Jinpeng Yang²Chunlei Yang²Zhi Wang^1*

• ¹Hubei University of Technology, Wuhan, China
• ²Tobacco Research Institute of Hubei Province, Wuhan, China

Cigar tobacco leaf (CTL) fermentation is an effective strategy to improve its aroma content and quality. Based on metagenomics data from the CTL natural fermentation process (24 d), this study investigated the metabolic migration characteristics of carbon sources, fatty acids, overflowed molecules, and amino acids (such as arginine). The phenomena of glucose metabolism limitation and a sequential utilization of carbon sources during the fermentation process were observed. The metabolic abundances of starch, sucrose, monosaccharides, xylose, glycerol, arginine, overflow molecules, malate, and citrate transmembrane transport were significantly reduced in the later fermentation stage (16-24 d). Meanwhile, arginine catabolism was the main enhanced pathway of amino acid metabolism during mid-fermentation (8-16 d). Based on the results above, optimized contents of malate, arginine, and phosphate were obtained by response surface analyses corresponding to 4.1 mg/g, 1.0 mg/g, and 2.0 mg/g, respectively. Application of these optimized additives to the CTL fermentation at pilot-scale level (100 kg CTLs/ box) significantly facilitated the CTL aroma content up to 1679.1 μg/g, representing a 1.83-fold increase over the control (natural fermentation). Additionally, the main contributor to energy metabolism comes from lipid catabolism. The results provide important support for industrial fermentation of CTL and theoretical support for the expansion of new knowledge in the field of high-lipid tobacco variety breeding.