Abstract:L-glutamine is the most abundant semi-essential amino acid in human fluids. It has a variety of nutritional and pharmacological functions and is widely used in medicine, food additives, nutritional health products, feed and other fields. At present, microbial fermentation is the main method to produce L-Gln, but its industrial application is seriously limited by the problems of low fermentation acid production efficiency, many by-products, and lack of bacterial performance. In order to solve those problems, the L-Gln production strain CGQ03 constructed early in our laboratory was used as the starting strain in this study. The synthesis of precursor L-glutamate was promoted by enhancing the expression of glutamate dehydrogenase and the supply of cofactor NADPH. The yield of L-Gln production was increased by enhancing the intracellular content of cofactor ATP, overexpressing the dissolved oxygen-related protein VHb to improve the oxygen carrying capacity of cells, enhancing the catalytic activity of key enzyme glutamine synthetase, and optimizing the fermentation process. The final genetically engineered strain CGQ08/pDXW10-glnASc-gdhCg was fed-batch fermented in a 5 L fermenter for 66 h, and the yield of L-Gln was up to (94.5±1.8) g/L, with the sugar-acid conversion rate of 34.8% and the production intensity of 1.43 g/(L·h). This study could provide an important reference for the industrial production ofL-Gln and its related compounds.
