The best condition selected in this study for the protoplast preparation is that: 15 hr for cell age . 0. 01 M for pretr经实验确认,原生质体制备最优条件为:取菌龄为15hr的菌体,以0.01mol/L的β—巯基乙醇预处理,蜗牛酶温浴时间为60min.