通过基因敲除构建了蛋氨酸合成途径关键酶基因metX缺失的重组谷氨酸棒杆菌R102δmetX。采用部分因子实验设计考察发酵培养基中各组分对重组菌产苏氨酸的影响。结果表明,葡萄糖、酵母粉和酶解酪素对产苏氨酸影响显著。继而采用最陡爬坡路径逼近最大响应区域,并结合中心组合实验和响应面对3个显著性因素进行分析,得到优化的发酵培养基组成:葡萄糖50.78 g/L,酵母粉6 g/L,酶解酪素0.99g/L,生物素80μg/L,VB1 2mg/L,CaCO3 20 g/L,(NH4)2SO4 15.15 g/L,MgSO4.7H2O 0.5 g/L,KH2PO4 0.5g/L,K2HPO4 0.5g/L,Fe-SO4.7H2O 0.02g/L,MnSO4.7H2O 0.02g/L,接种量8%。采用该优化培养基,供试菌株的胞外苏氨酸浓度为3.35g/L,较优化前提高了30%。

The recombinant Corynebacterium glutamicum R102δmetX(R102 with deletion in the metX gene) was constructed.Fractional factorial design was used to evaluate the effects of medium components on the production of threonine.Glucose,yeast extract and enzymatic casein were the most important factors among twelve tested variables that influence the production of threonine.Based on the experimental results,the path of steepest ascent was undertaken to approach the optimal region of these factors.Central composite design and response surface analysis were subsequently employed for further optimization.The optimal medium for threonine synthesis was composed of;glucose 50.78g/L,yeast extract 6 g/L,enzymatic casein 0.99 g/L,biotin 80μg /L,VB1 2mg/L,CaCO3 20g/L,(NH4)2SO4 15.15 g/L,MgSO4·7H2O 0.5 g/L,KH2PO4 0.5 g/L,K2HPO4 0.5 g/L,FeSO4·7H2O 0.02 g/L,MnSO4·7H2O 0.02g/L,inoculation quantity 8%.Under the optimum conditions,the threonine yield of the recombinant strain was 3.35g/L,which was 30% higher than the original medium components.