Wild-type strains isolated from nature cannot be directly used for production, and generally need to be treated. In order to obtain products that meet people's requirements in variety, yield and quality through fermentation engineering, we must first have strains with excellent characteristics. At first, people looked for the needed strains from nature, but the yield of strains obtained by this method was generally low, which could not meet the needs of industry.
Corynebacterium glutamicum can use glucose to form glutamic acid through complex metabolic process; However, when the final product, glutamic acid, is over-synthesized, the activity of glutamate dehydrogenase will be inhibited, resulting in the interruption of synthesis pathway. When the concentration of glutamic acid decreases due to consumption, the inhibition will be lifted and the synthesis reaction will start again. Generally speaking, microbial cells do not accumulate a large number of metabolites. But in industrial production, people always hope that microorganisms can accumulate useful metabolites to the maximum extent, which requires manual control of microbial metabolism. Therefore, in the process of glutamic acid production, some measures can be taken to change the permeability of cell membrane, so that glutamic acid can be quickly excreted from the cell, thus relieving the inhibitory effect of glutamic acid on glutamic acid dehydrogenase and improving the yield of glutamic acid.