Screening and identification of tannin-degrading bacteria to optimize fermentation of cigar tobacco

In order to reduce tannin contents (mass fraction) and bitterness of cigar tobacco and to improve the overall leaf quality, 16 tannin-degrading bacterial strains were screened from the surface of cigar tobacco leaves. Among them, strain B-3 had the strongest enzyme-producing ability according to the tannase activity assay and was identified as Pantoea agglomerans. Different types of carbon sources, nitrogen sources, and inorganic salts were selected and different concentration gradients were set to screen the optimal enzyme-producing medium for strain B-3. The tannase activity of the enzyme solution produced by strain B-3 on the optimal enzyme-producing medium (sucrose 15.45 g/L, yeast extract 17.00 g/L, NaCl 4.94 g/L) reached 55.83 U/mL, which was 121.28% higher than that on the basic enzyme-producing medium. The enzyme solution was diluted with sterile water to obtain a tannase activity of 5.58 U/mL. When Indonesian cigar tobacco leaves were fermented with the diluted enzyme solution at a mass ratio of 25% and at 45 ℃ for 7 days, the tannin degradation rate was 39.69%, and the bitterness and offensive odor of the leaves were reduced.