Exoproduction and Biochemical Characterization of a Novel Serine Protease from L9 with Hide-Dehairing Activity.

This study is the first report on production and characterization of the enzyme from an species. A 4.2-fold increase in the extracellular protease (called L9) production from L9 was achieved through the one-factor-at-a-time approach and response surface methodological optimization. L9 protease exhibited a unique protein band with a mass of 25.9 kDa upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This novel protease was active over a range of pH (4-13), temperatures (30-80°C) and salt concentrations (0-220 g/l), with the maximal activity observed at pH 7, 70°C and 20 g/l NaCl. Proteolytic activity was upgraded in the presence of Ag, Ca and Sr, but was totally suppressed by 5 mM phenylmethylsulfonyl fluoride, which suggests that this enzyme belongs to the serine protease family. L9 protease was resistant to certain common organic solvents and surfactants; particularly, 5 mM Tween 20 and Tween 80 improved the activity by 63 and 15%, respectively. More importantly, L9 protease was found to be effective in dehairing of goatskins, cowhides and rabbit-skins without damaging the collagen fibers. These properties confirm the feasibility of L9 protease in industrial applications, especially in leather processing.