串联表达NAD激酶和谷氨酸脱氢酶基因对L-谷氨酸产量的影响

由ppnk和gdh编码的NAD激酶和谷氨酸脱氢酶是L-谷氨酸合成途径中的两个重要酶。以谷氨酸生产菌CN1021基因组为模板PCR扩增ppnk和gdh基因并转化至该菌中,检测上述两个基因单独表达和串联表达对L-谷氨酸产量的影响。结果表明,当两个基因单独过表达时,其酶活性分别提高2.4和2.1倍,L-谷氨酸产量分别提高7.9%和1.4%。当将两个基因串联表达时,其酶活性分别提高2.0和1.5倍,L-谷氨酸的产量却提高了13.2%。说明过表达ppnk和gdh能够有效提高L-谷氨酸产量,且具有协同作用。

Effect of Co-expression of ppnk and gdh on L-glutamate Production

The ppnk and gdh encoding NAD kinase (NADK) and glutamate dehydrogenase (GDH) were two important enzymes in the glutamate biosynthesis pathway. The two genes were amplified by polymerase chain reaction (PCR) from the glutamate-producing strain CN1021. The specific activity of NAD kinase in extracts was increased by 2.4-fold, and GDH, by 2.1-fold. When both genes were co-expressed in CN1021, the activity of NADK and GDH were increased by 2.0-fold and 1.5-fold, respectively. The flask fermentation results showed that the separate over-expression of ppnk and gdh in CN1021 approximately 7.9% higher and 1.4% more L-glutamate than the original strain, moreover, co-expressing the two genes strain exhibited 13.2% higher L-glutamate. Taken together, the results demonstrated that co-expression of gdh and ppnk genes can significantly improve the production of L-glutamate.