on an orbital shaker
(Thermoshake THO 500, Gerhardt Analytical Systems, Germany)
set up at 120 rpm for 24 h at 25 C. Cells were collected by
centrifugation for 10 min at 16,000 g, washed twice with 0.05 M
phosphate buffer (pH 7), and then suspended in sterile distilled
water. Finally, the cells were counted