柠檬酸产生菌黑曲霉经多次物理、化学诱变处理后会对其产生一定的抗性,在菌种改良过程中不易得到优良高产菌株。为此,以黑曲霉(Aspergillus niger)28#为出发菌株,采用金属盐类化合物—LiCl处理黑曲霉的孢子,然后用He-Ne激光辐照对柠檬酸发酵菌黑曲霉进行复合诱变。结果表明,各实验组发生了明显的不同变化,说明该方法能诱发黑曲霉细胞的遗传变异,适合于菌种的改良选育。研究采用玉米粉为原料,摇瓶发酵时间72h,发酵温度35±1℃,通过溴甲酚绿指示性平板辅助筛选和摇瓶发酵,筛选出了3株柠檬酸发酵高产突变菌株,柠檬酸产酸率提高了19.29%,转化率从87.07%提高到103.86%,其中菌株L42遗传相对稳定,可作为进一步诱变筛选的出发菌株。

The Aspergillus niger mutated by physical and chemical methods many times could produce resistance for some mutagens.In order to solve the antimutagenic effect,the strain 28# of Aspergillus niger was mutated by LiCl and He-Ne laser in this paper.The spores irradiated were then cultured and fermentated.Variations in survival rates of the spores,rates of growth,and propagation of the hypahe,yield of the main metabolite citric acid,etc.were determined and analysed.The results show that the various experimental groups had changes in different degrees.This indicates that this way can induce Aspergillus niger cells to mutate and may possibly be applied to selectively breed new good quality strains with high yield for production of citric acid.Three mutatant strains Aspergillus niger with relatively high yield of citric acid produced from corn starch were obtained.In flask with the optimized fermentation temperature(35±1)℃ and period(72hrs),by auxiliary screening with bromocresol green indicator and shake fermentation,the yield of citric acid increased 19.29%,and the comersation rate of glucose to citric acid increased from 87.07%to 103.86%.The results show that the mutant strain L42 have high genetic stability,and could be used for further breeding work of the citric acid fermentation by Aspergillus niger.