Extraction of Cell-envelope Proteinase from Lactobacillus fermentum

Lysozyme treatment was selected out of three commonly used ways for extracting cell-envelope protainase from Lactobacillus fermentum cells in the present study. The composition and pH of cell lysis solution and three extraction conditions were optimized using orthogonal array design. The best cell lysis solution was a mixture of 50 mmol/L Tris-HCl,150 mmol/L NaCl,3% Tween-20 and 2 mg/mL lysozyme at pH 8.9. Cell lysis solution/ Lactobacillus fermentum cells ratio of 10:1 (V/m) and incubation time of 5 h at a constant temperature of 37 ℃ were found optimal for the extraction of cell-envelope protainase,and the maximum specific enzyme activity was up to 38.957 U/mg under these conditions.