诱变筛选Vc二步伴生菌

Mutagenesis screening Vc two-step companion bacteria

为了提高Vc二步发酵糖酸转化率,以巨大芽孢杆菌WS-05为出发菌株,采用微波和氯化锂复合诱变的方法进行诱变选育,筛选促进产酸菌生长和代谢的伴生菌。研究了微波-氯化锂诱变过程中不同的剂量、时间对Vc二步伴生菌存活率的影响,选取菌株存活率为55%~70%的3组诱变组合方式进行诱变,筛选能使小菌发酵产2-酮基-L-古龙酸产量高的伴生菌,经摇瓶发酵复筛,获得高产菌株D06,其转化率较出发菌株高2%。研究了发酵条件对新菌系的影响,结果显示:适当增加新菌系通气量(250 mL发酵摇瓶中装液20~25 mL)可以充分满足菌体代谢产酸对氧的要求,最适底糖浓度为7%,最适生长温度为31℃;经传代实验证明,其遗传性状稳定,4代平均转化率可达87.84%。

In order to improve the conversion rate of sugar and acid in Vc two-step fermentation,bacillus giant WS-05 was used as the starting strain,and the combined mutagenesis method of microwave and lithium chloride was used for mutagenesis selection,and the associated bacteria that were more conducive to the growth and metabolism of acid-producing bacteria were screened.The effects of dose and time of microwave-lithium chloride mutagenesis on the survival rate of Vc two-step associated bacteria were studied.Three groups of mutagenesis doses with survival rate of 55%~70%were selected for mutagenesis.Screening the associated bacteria that can ferment small bacteria to produce 2-keto-L-gulonic acid with high yield,The high-yielding strain D06 was obtained by shaking flask fermentation and re-screening.The conversion rate of the strain was 2%higher than that of the original strain.The effect of fermentation conditions on the new strains was studied.The results showed that the oxygen requirement of the bacteria for acid production could be fully met by appropriately increasing the ventilation volume of the new strains(20~25 mL liquid in 250 mL fermentation shaker),the optimal concentration of basal sugar was 7%,and the optimal growth temperature was 31℃.It was proved that the genetic character was stable,Its genetic character is stable,and the average conversion rate of 4 generations can reach 87.84%.