The Construction of Corynebacterium glutamicum for Producing γ-Aminobutyric Acid and Analysis of the Fermentation Process

In this study, we constructed a recombinant Corynebacterium glutamicum strain for γ-aminobutyric acid (GABA) biosynthesis via the heterologous expression of glutamate decarboxylase (GAD) derived from Lactiplantibacillus plantarum. We systematically analyzed the fermentation strategy, the balance between cell growth and GAD expression, and the intracellular and extracellular glutamate and GABA levels during fermentation in recombinant C. glutamicum. The results demonstrated that a fermentation strategy combining variable-rate feeding with two-stage pH control at an initial glucose concentration of 50 g/L effectively enhanced cell proliferation, facilitated continuous glutamate synthesis and improved the catalytic efficiency of GAD. The intracellular and extracellular GABA synthesis improved up to 3.231 ± 0.024 g/L (a six-fold increase compared to the uncontrolled supplementation conditions). Furthermore, we fitted empirical equations relating cell growth, glucose consumption, GAD activity, and GABA synthesis during the fermentation. The maximum specific growth rate, glucose consumption rate, and GABA synthesis rate of recombinant C. glutamicum were 0.316 h−1, 1.407 g/(g∙h), and 0.0697 g/L/h, respectively. The fermentation regulation strategy and the dynamic analysis of the fermentation process in this study provide support for future metabolic regulation strategies.