牛源性蛋氨酸生产菌的分离筛选及发酵条件优化

Isolation and identification of bovine-derived methionine producing strain and optimization of fermentation conditions

为了从奶牛瘤胃中筛选出高产蛋氨酸微生物,无菌采集10份成年奶牛瘤胃内容物样本,经分离筛选得到18株菌株,将这些菌株进行分离纯化培养,并利用HPLC法检测各菌株发酵液中蛋氨酸的含量,最终筛选出1株蛋氨酸含量较高的菌株。经过形态观察和16S rDNA序列分析,该菌株与甲基营养型芽孢杆菌(Bacillus methylotrophicus)之间的同源性为100%。利用单因素试验确定了摇瓶发酵的最优条件:葡萄糖15%,硫酸铵3.5%,玉米浆2.5%,磷酸氢二钾1.5%,发酵时间为72 h,装液量为50 mL/500 mL。在最优条件下进行发酵试验,蛋氨酸产量提高到平均2.40 g/L,较发酵优化前产量提高了175.86%。

In order to screen out the high yield of methionine strain from cow rumen,10 cow rumen samples was collected,and 18 strains of bacillus were isolated and purified. Determination of methionine in fermentation liquid of each strain was made by HPLC method and one strain with high content of methionine was screened out. The strain was classified as Bacillus methylotrophicus according to the results of morphological observation and 16 S rDNA sequence analysis. The optimum condition of shaking flask fermentation was determined by single factor experiment. Results showed that glucose 15%,ammonium sulfate 3. 5%,corn syrup 2. 5%,K_2HPO_4 1. 5%,fermentation time 72 h and the liquid volume 50 mL/500 mL was preferred. Under the optimum conditions,the yield of methionine increased to an average of 2. 40 g/L,compared with the former has increased 175. 86%.