Abstract:Objective To improve the overall quality of upper tobacco leaves.Methods We isolated a hemicellulase-producing bacterium from tobacco soil and identified it as Actinacidiphila bryophytorum. After optimizing the culture conditions of this strain, we prepared the crude enzyme liquid, which was sprayed on upper tobacco leaves. The physical properties and chemical composition of the treated tobacco leaves were then evaluated.Results The optimal fermentation conditions for the strain were an inoculation rate of 4%, pH 6.0, and incubation at 30 ℃ for 36 h. Enzyme preparations of different concentrations (50, 100, 150, 200 and 250 U/mL) were then sprayed on the surface of upper tobacco leaves, and the appearance quality, conventional chemical composition, lignocellulose content, and sensory scores of the tobacco leaves were evaluated. The results indicated that treatment of the enzyme preparation at 150 U/mL performed better than other treatments. Compared with the control group, the 150 U/mL treatment increased the overall score for the appearance quality (maturity, color, characteristics, and structure) of tobacco leaves by 5.15 points. Additionally, this treatment increased the total sugar content and reducing sugar content by 29.87% and 35.77%, respectively. Meanwhile, it decreased the content of nicotine, cellulose, hemicellulose, and lignin by 16.10%, 16.37%, 20.22%, and 17.13%, respectively. Furthermore, the aroma characteristics were enhanced, and off-flavors were reduced.Conclusion The enzyme preparation produced by the fermentation of A. bryophytorum S2 improves the appearance quality, increases the soluble total sugar and reducing sugar content, and reduces the lignocellulose content of tobacco leaves, thus improving the overall quality of tobacco leaves.