Aspergillus niger TN09,is a citric acid producing strain. In order to further improve the production of citric acid, citric acid production fungus Aspergillus niger TN09,was mutagenesised by plasma. The spore suspension after mutagenesis, which was cultured 72,h at 35,℃,was spread on the liquid medium of the liquefied corn. Then the diameter of the transpar-ent circle was measured. It is considered as citric screening strains if the diameter of the transparent circle of the colony was greater than 2.2,cm,the diameter of the colony was greater than 0.5,cm,and the ratio was greater than 4.8,coloneis. A high-yielding strain was obtained through shake flask rescreening. The new strainhas genetic stability and the citric acid yield increased by 8.67% compared with that of the original strain(yield of citric acid 12.46,g/dL).%黑曲霉TN09是1株柠檬酸生产菌株．为了进一步提高柠檬酸的生产水平，利用等离子对柠檬酸生产菌黑曲霉 TN09进行了诱变．诱变后的孢子悬液涂布玉米液化液平板，35,℃培养至72,h测量透明圈直径，以酸解透明圈直径大于2.2,cm、菌落直径大于0.5,cm、其比值大于4.8的菌落作为初筛柠檬酸菌株，然后进行摇瓶复筛获得了1株遗传性能稳定的高产菌，与出发菌株(产酸12.46,g/dL)相比产酸增幅达到8.67%．
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