Abstract: In this study, the extraction of cell-envelope proteinase (CEP) from Lactobacillus acidophilus was optimized. A comparison of ultrasonic treatment, Ca2+-free treatment and lysozyme lysis for their effectiveness in Lactobacillus acidophilus cell disruption was performed to determine lysozyme lysis as the best method among the three. Further, process conditions optimization for CEP extraction from Lactobacillus acidophilus by lysozyme lysis was carried out using orthogonal array design based on one-factor-at-a-time experiments. The best extraction results were obtained by 3 h incubation at 37 ℃ of Lactobacillus acidophilus cells in pH 7.8 lysozyme lysis buffer containing 50 mmol/L Tris-HCl, 100 mmol/L NaCl, 1% TritonX-100 and 1.5 mg/mL lysozyme and then centrifugation at 4500 r/min and 4 ℃ for 20 min, and the resulting supernatant was collected as CEP. In addition, lysozyme concentration had the largest impact on extraction efficiency of CEP followed by pH, Tirton X-100 concentration and incubation time.

Key words: Lactobacillus acidophilus, cell-envelope proteinase (CEP), extraction