乳链菌肽的分离纯化和部分生物学性质

用乳酸链球菌ＳＭ５２６进行乳链菌肽的发酵生产，产量为４０～５０ｍｇ／ｌ．经中空纤维超滤器超滤，非极性大孔吸附树脂ＸＡＤ－２层析，ＣＭ－ＳｅｐｈａｄｅｘＣ－２５层析和ＳｅｐｈａｄｅｘＧ－５０层析纯化了该肽。ＳＤＳ－ＰＡＧＥ表明达均一，ＲＰ－ＨＰＬＣ表明其纯度不低于９５％。ＳＤＳ－ＰＡＧＥ测其Ｍｒ约为３６００，用ＩＥＦ测其等电点为９．５．酸性条件下稳定且抗热；对胰蛋白酶、胃蛋白酶和木瓜蛋白酶不敏感，但对α－胰凝乳酶和蛋白酶Ｋ敏感。乳链菌肽对多种革兰氏阳性菌有强烈的抑制作用；以枯草杆菌和金黄色葡萄球菌为指示菌，其作用方式是杀菌。

Purification and Partial Biological Characterization of Nisin

Streptococcus lactis SM526 was used for nisin production with a yield of 40-50 mg/L. Nisin was purified by a four-step purification, including ultrafiltration and column chromatography on Amberlite XAD-2,CM-Sephadex C-25 and Sephadex G-50 and demonstrated to be homogenous by SDS-PGAE and IEF experiments. The degrees of purity exceeded 95 % as estimated by HPLC analysis. The molecular mass of nisin was approximately 3. 6 kD by SDSPAGE analysis. The isoelectric point was estimatied to be around PHg.5 by IEF experiment. It was shown to be heat tolerant and stable in acid conditions. Rapid inactivation of nisin occured in the presence of a-chymotrypsin and proteinase K,but no decrease in activity could be detected after incubation for 2h in the presence of trypsin,pepsin and papain. Furthermore, nisin exhibited great inhibitory effect upon various Gram-positive bacteria. For mode of action,it revealed a bacteriocidal mode against Barillus subtilis and Staphylococcus aureus.