麦芽三糖生成酶高产菌株的选育

Breeding of high- yielding strains of maltotriose- forming enzyme

以蛾微杆菌(Microbacterium imperiale)Mebl-012菌株为出发菌株,利用常压室温等离子体(atmospheric and room temperature plasma,ARTP)和紫外复合诱变,筛选麦芽三糖生成酶高酶活菌株。将不同ARTP致死率下的菌悬液进行了混合,均匀涂布筛选平板进行初筛,之后用摇瓶发酵进行复筛,最终筛选出了一株麦芽三糖生成酶高产突变菌株Microbacterium imperiale Metp-57,酶活达到241.32 U/m L,较出发菌株Mebl-012(产量为116.43 U/m L)提高了107.26%。以ARTP诱变过程中筛选出的高产菌株Metp-57为出发菌株,进行紫外诱变处理,得到高产突变株Metu-24,其麦芽三糖生成酶酶活可达到408.41 U/m L,较原始菌株Mebl-012提高了250.77%,且遗传性状稳定。突变株Metu-24较原始菌株Mebl-012的生长速率有明显提高。以本实验麦芽三糖生成酶水解淀粉,制备的麦芽三糖糖浆中麦芽三糖占主要成分,含量达到46.7%。

The Microbacterium imperiale of Mebl-012 was selected as the original strain, and the composite mutagenesis of Atmospheric and room temperature plasma（ARTP）-UV were used to treat it, in order to obtain a strain of high maltotriose-forming enzyme activity.The bacterial suspension under different ARTP mortality rates were mixed, and then were coated filter plate, followed by fermentation rescreening. Eventually a high-yielding strain Microbacterium imperiale of Metp-57 was screened out, production of this strain reached 241.32 U/mL, which was increased by 107.26% comparing with the original strain Mebl-012（yield of 116.43 U/mL）.Choosing high-producing strain Metp-57 as starting strain, UV mutagenesis was conducted, maltotriose-forming enzyme activity of the mutant Metu-24 reached 408.41 U/mL,which was increased by 250.77% compared with the original strain Mebl-012,and its genetic stability was good.Compared with the original strain Mebl-012,the growth rate of metant strains Metu-24 was significantly improved.Hydrolyzing starch by this enzyme,maltotriose was predominant component,maltotriose content reached 46.7% in maltotriose syrup.