Abstract：How to use exogenous enzyme effectively to degradate the protein in tobacco leaf,improving tobacco quality is a new research task in tobacco industry. A protease high-yielding strain was isolated from the surface of Yuxi tobacco(Nicotiana tabacum) leaves.The strain was cultivated and the protease was concentrated from the strain fermentation metabolites, protease activities and characterization of the enzyme were introduced in this paper. Orthogonal test was designed to detect the effection of enzyme quantity(40, 80 and 120 U/g)，temperature (25, 35 and 45 ℃), relative humidity(50%、60% and 70%)) and reaction time(30, 60 and 90 h) to tabacco protein, aroma component was also analzsed under optimal conditions. Results illustrated that the activity of Bacillus pumilus strain B1 was 4 200 U/mL, the highest activity was under the conditions of pH 6.0 and 50 ℃. The optimal conditions for the enzyme was enzyme quantity120 U/g, temperature 35 ℃, relative humidity 70%, reaction time 60 h, the degradability rate of protein was 18.64% and the amino acid increased 12.72%, GC/MS showed that the amount of volatile aroma content increased significantly. The results suggested that the enzyme produced by the strain B1 isolated from the surface of Yu Xi tobacco leaves can degrade protein in flue-cured tobacco leaves, increasing the availability of lower - grade variety of tabacco, improving the qudlity of tabacco leave. And The enzymes can be applied in industrial production.
