维吉尼亚链霉菌物理诱变及外源添加氯化镧对VGM产量的影响

目的 利用物理诱变结合链霉素抗性筛选维吉尼亚霉素(VGM)高产菌株维吉尼亚链霉菌，并考察外源添加稀土元素氯化镧对维吉尼亚链霉菌发酵的影响。方法 一方面，以链霉素为筛选剂建立孢子致死突变标志的微波及紫外诱变两种筛选模型，采用管碟法获得抑菌圈直径较大的作为初筛菌株，再通过摇瓶复筛进一步确定高产菌株。另一方面，在发酵培养基中外源添加3~30mg/L的氯化镧，考查其对链霉菌合成VGM的影响。结果 比较两种筛选模型，基于链霉素的微波诱变效果较好，正突变率高达32.83%；并获得一株高产菌株MW 178(146.72±11.80)μg/mL，较出发菌株(21.24±1.34)μg/mL提高了约6倍。在发酵初始时，外源添加10mg/L氯化镧，VGM的产量由146.72μg/mL提高到180.01μg/mL，提高了约22.69%。结论 采用微波诱变结合链霉素抗性筛选的方法可以获得VGM高产突变株；在发酵初始时，外源添加适量氯化镧可以显著提高VGM产量。

Studies on the physical mutagenesis of virginiamycin producing Streptomyces virginiae and the impact of lanthanum on antibiotic productivity

Objective A method of physical mutagenesis coupled with streptomycin resitance screening was applied to select virginiamycin (VGM) high-producing strain. Also, the effect of adding lanthanum chloride on the production of VGM was studied. Methods First, two streptomycin-resistance mutational labelling selection models with physical mutagenic factor (microwave and ultraviolet) were built to screen high-yield mutants. Then preliminary positive strains were picked out by measurement of the inhibitory activity to Micrococcus luteus. And the subsequent determination by HPLC were carried out for the high VGM-producing strains cultivated in the shake-flask. Finally, lanthanum chloride was added in fermentation medium of the strain with the concentration of 3~30mg/L. Results The mutagenesis of microwave combined with streptomycin resistance was better and the positive mutation rate was up to 32.83%. Streptomycin-resistant mutant strain MW 178 was got by microwave producing VGM with yield of (146.72±11.80)μg/mL which beyond six times higher than the initial strain (21.24±1.34)μg/mL. The production of MW 178 reached up to 180.01μg/mL eventually by adding the concentration of 10mg/L lanthanum chloride to the medium at the beginning of the fermentation. Conclusion Microwave mutation compound streptomycin resistance screening is effetive for screening high-yeilding mutants and the addition of lanthanum chloride could significantly improve the yield of