为使乳酸乳球菌适应玉米酒糟作为发酵生产乳酸链球菌素(Nisin)的主要氮源,首先对培养基进行了初步优化,发现在酒糟清液中加入蔗糖、酵母膏和磷酸氢二钾明显促进了乳酸乳球菌的生长.在此基础上,使用等离子体对乳酸乳球菌进行诱变处理,利用24方孔深孔板技术可实现对高产Nisin突变菌株的选择性筛选.结果表明,诱变菌株在只有5.0%存活率时,得到的正突变菌株可达26.2%.借助摇瓶发酵实验对其生产Nisin的发酵水平进行研究,发现有1株诱变选育菌株发酵Nisin的活性高达6 520 U/mL,并且其发酵能力比诱变起始菌株能力更强.
Corn thick mash was used as main nitrogen source to produce Nisin.Firsty,the fermentation media were optimized by single factor experiment.The results indicated that the growth of Lactococcus lactis was obviously enhanced by adding sucrose,yeast extract and K2HPO4 to thick mash.As the starting strain,the strain was further treated by atmospheric and room temperature plasmas and quickly selected using 24 well culture plate.At a survival rate of 5%,the positive mutation rate of the Lactococcus lactis was found to be 26.2% evaluated by the comparison with the starting strain.The results from shake flask culture further confirmed that a positive mutant strains could produce 6 520 IU/mL Nisin.
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