Tea-derived Bacillus licheniformis and Aspergillus neoniger modulate microbial community and flavor quality of cigar tobacco leaves during fermentation

Cigar tobacco quality formation depends on microbially mediated macromolecular degradation and flavor compound formation during fermentation. However, the regulatory mechanisms by which tea‑derived microorganisms optimize this process remain unclear. Herein, two tea‑derived strains, Bacillus licheniformis T1‑S1 and Aspergillus neoniger T3‑S3, were evaluated as inoculants for cigar tobacco leaf fermentation. Bacillus licheniformis T1‑S1 increased the contents of specific alcohol compounds (phenylethyl alcohol and cedrol), whereas Aspergillus neoniger T3‑S3 promoted the accumulation of ketones, acids, and alcohols. Notably, Aspergillus neoniger T3‑S3 increased total aroma content by 17% and neophytadiene by 21.4% relative to the control. In contrast, Bacillus licheniformis T1‑S1 reduced neophytadiene content by approximately 50% while maintaining soluble sugar stability. Sensory evaluation confirmed that Aspergillus neoniger T3‑S3 could alleviate smoke irritation and improve fineness, sweetness, and aftertaste. Both strains altered microbial community composition. Aspergillus neoniger T3-S3 reduced fungal diversity, whereas Bacillus licheniformis T1-S1 decreased bacterial richness without significantly affecting bacterial diversity. Correlation analyses further revealed distinct associations between core microbial genera and aroma compounds. Alkaloids, acids, esters, phytol, 3‑ethyl‑3,4‑dihydro‑2(1 H)‑quinoxalinone, and 2,4,6-trimethyl-benzenepropanol were significantly correlated with sensory performance. Overall, this study provides a theoretical basis and a practical strategy for the targeted regulation of cigar tobacco leaf fermentation using tea-derived microorganisms, supporting efficient, high-quality cigar tobacco production.