Methods:The influence of ammonium sulfate and glucose on plasmid stability and penicillin G acylase activity were conducted in flask shakes and a 5L fermentor.

• 发酵过程中维持低葡萄糖水平可以限制细胞的生长速率,提高质粒稳定性和促进青霉素G酰化酶的合成。