Identification of key molds in cigar tobacco leaves and screening mildew inhibition effects of antagonistic strains

To clarify the microorganism species that cause mildew in cigar tobacco leaves and screen antagonistic strains to control mildew in fermented cigar tobacco leaves, molds and potential antagonistic strains in moldy cigar tobacco leaves from Hubei Province in China and cigar tobacco producing regions in Dominican Republic were isolated and purified. Microorganisms were identified by combining morphological and molecular biological methods, and the inhibitory effects of antagonistic strains on mildew were evaluated through a plate antagonism assay and a fermentation inhibition test on cigar tobacco leaves. The results indicated that the primary mold in moldy leaves from Hubei Province were Penicillium, followed by Aspergillus; and the primary mold in moldy leaves from Dominican Republic were Sarocladium, followed by Penicillium. Four culture-dependent molds, including Penicillium citrinum, Penicillium sumatraense, Aspergillus westerdijkiae, and Scopulariopsis brevicaulis were isolated from the samples. Two strains exhibiting good antagonistic effects against molds were identified as Bacillus velezensis and Bacillus safensis, with inhibition rates of 96.94% and 40.67%, respectively. Especially, Bacillus velezensis was effective in mildew inhibition during the fermentation of cigar tobacco leaves.