Isolation, Identification and Biological Characterization of Mold Species from Industrial Fermented Cigar Tobacco Leaves

To identify the mold species during the industrial fermentation process of cigar tobacco leaves, fungi were isolated and purified from the surface of moldy cigar tobacco leaves, and were identified with the combination of morphological and molecular techniques. The biological characteristics of mold were also investigated. The results showed that the main mold causing moldiness of cigar tobacco leaves were Aspergillus in this study, and three strains of mold were identified as A. tabacinus, A. flavus and A. montevidensis. The growth rate of the three mold strains were in the order of A. flavus > A. tabacinus > A. montevidensis on different culture media. All three mold strains could grow at 25℃ to 35℃, only A. flavus could grow at 40℃, and none of the strains could grow at 45℃or higher temperature. The optimal pH for A. flavus was 4, while A. tabacinus and A. montevidensis were most suitable for pH 8-9. All three mold strains were sensitive to UV radiation, and after 15 minutes of exposure, the mortality rate was over 90%. Overall, the results from this study indicated that the three types of Aspergillus that cause cigar tobacco leaf mold during industrial fermentation are A. tabacinus, A. flavus and A. montevidensis. The rational use of ultraviolet irradiation is important for mold control and prevention.