中文摘要：

采用带水循环冷却器的微波装置，在低功率微波条件下，对干酪乳杆菌鼠李糖亚种（Lactobacillus casei subsp．rhamnosus）X1—12进行诱变处理，在微波功率为400W、辐射时间3min的诱变条件下得到一突变菌株W4-3-9，其L-乳酸产量为115．8g／L，比原始菌株X1-12提高了58．0％，连续遗传10代，产酸性状稳定．采用原子力显微镜（AFM）对未辐射的原始菌株和高产酸的突变菌株的表面形态和DNA进行观察对比，获得了微波辐射前后干酪乳杆菌的细胞表面形态和DNA的AFM图像．

英文摘要：

With low power microwave irradiations,a mutation process of Lactobacillus casei subsp, rhamnosus X1-12 occurred in a microwave device with water circulation cooler. Under the conditions of microwave power of 400 W and irradiation time of 3 min,a mutated strain W4-3-9,a kind of L-lactic acid high-yielding strain, was obtained. Compared with the starting strain X1-12 ,the L-lactic acid production of W4-3-9 was increased by 58.0% ,up to a concentration of 115.8 g/L. The strain still remained the characteristics of high L-lactic acid production after subcultured repeatedly for about 10 times and stored for two months. The images of cell surface morphology and DNA of parent and mutated strains were obtained and compared by atomic force microscopy （AFM）.