2.5 SDS-PAGE analysis
The cells from 1 mL of fermentation broth were collected by centrifugation at 12000rpm for 10 min, and the supernatant was discarded. The cells were resuspended in 1 mL of 20 mM Tris-HCl buffer (pH 7.5) and disrupted using an Ultrasonic Cell Disruptor (operating for 5s, pausing for 5s, 40 times). The cell lysate was centrifuged at 4 °C, 12000 rpm for 10 min, and the soluble protein remained in the supernatant. An 80 μL aliquot of the supernatant was mixed with 20 μL of 5×loading buffer, and heated in a 100 °C metal bath for 10 min. The final protein samples were used for SDS-PAGE. Samples corresponding to 0.15 OD (10-well gel) or 0.075 OD (15-well gel) were added to the corresponding protein gel wells, and powered on until the electrophoresis was complete.