Rational metabolic engineering of <i>Corynebacterium glutamicum</i> for efficient synthesis of L-glutamate.

Jiafeng Liu; Zhina Qiao; Youxi Zhao; Meijuan XU; Xian Zhang; Taowei Yang; Zhiming Rao

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Rational metabolic engineering of Corynebacterium glutamicum for efficient synthesis of L-glutamate.

Author: Jiafeng LIU ¹ ; Zhina QIAO ¹ ; Youxi ZHAO ² ; Meijuan XU ¹ ; Xian ZHANG ¹ ; Taowei YANG ¹ ; Zhiming RAO ¹
Author Information

1. School of Biotechnology, Jiangnan University, Wuxi 214122, Jiangsu, China.
2. College of Biochemical Engineering, Beijing Union University, Beijing 100023, China.
Publication Type:Journal Article
Keywords: Corynebacterium glutamicum; glutamate; glutamate transporter; ribosome-binding site (RBS) sequence optimization; transcription analysis
MeSH: Glutamic Acid; Corynebacterium glutamicum/genetics*; Ketoglutaric Acids; Metabolic Engineering; Alanine
From: Chinese Journal of Biotechnology 2023;39(8):3273-3289
CountryChina
Language:Chinese
Abstract: L-glutamic acid is the world's largest bulk amino acid product that is widely used in the food, pharmaceutical and chemical industries. Using Corynebacterium glutamicum G01 as the starting strain, the fermentation by-product alanine content was firstly reduced by knocking out the gene encoding alanine aminotransferase (alaT), a major by-product related to alanine synthesis. Secondly, since the α-ketoglutarate node carbon flow plays an important role in glutamate synthesis, the ribosome-binding site (RBS) sequence optimization was used to reduce the activity of α-ketoglutarate dehydrogenase and enhance the glutamate anabolic flow. The endogenous conversion of α-ketoglutarate to glutamate was also enhanced by screening different glutamate dehydrogenase. Subsequently, the glutamate transporter was rationally desgined to improve the glutamate efflux capacity. Finally, the fermentation conditions of the strain constructed using the above strategy were optimized in 5 L fermenters by a gradient temperature increase combined with a batch replenishment strategy. The glutamic acid production reached (135.33±4.68) g/L, which was 41.2% higher than that of the original strain (96.53±2.32) g/L. The yield was 55.8%, which was 11.6% higher than that of the original strain (44.2%). The combined strategy improved the titer and the yield of glutamic acid, which provides a reference for the metabolic modification of glutamic acid producing strains.