title: Specific γ-aminobutyric acid decomposition by gabP and gabT under neutral pH in recombinant Corynebacterium glutamicum.
abstract: OBJECTIVE
  Corynebacterium glutamicum that expresses the exogenous L-glutamate decarboxylase (GAD) gene can synthesize γ-aminobutyric acid (GABA). To prevent GABA decomposition in the recombinant C. glutamicum GAD strain, GABA uptake and the GABA shunt pathway were blocked.
  
  
  RESULTS
  GABA uptake is catalyzed by GABA permease encoded by gabP. The first reaction of the GABA shunt pathway is catalyzed by the GABA transaminase encoded by gabT. Initially, the effects of pH on GABA decomposition in recombinant C. glutamicum co-expressing two GAD genes (gadB1 and gadB2) were analyzed, demonstrating that GABA could be decomposed under neutral pH. Next, the gabP and gabT were individually deleted, and the GABA production of the related GAD strains was investigated by controlling the pH of the final fermentation stage at a neutral state. During this stage, the GABA concentration of the gabT-deleted GAD strain decreased from 23.9 ± 1.8 to 17.7 ± 0.7 g/l. However, the GABA concentration of the gabP-deleted GAD strain remained at 18.6-19.4 g/l.
  
  
  CONCLUSIONS
  This study demonstrated that GABA was decomposed under neutral pH and that the deletion of gabP could effectively alleviate GABA decomposition in C. glutamicum.
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China. 164083507@qq.com.|Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China. 164083507@qq.com.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China. 164083507@qq.com.
authors.forename: Yalan
authors.initials: Y
authors.lastname: Ni
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China. shifeng@jiangnan.edu.cn.|Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China. shifeng@jiangnan.edu.cn.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China. shifeng@jiangnan.edu.cn.
authors.forename: Feng
authors.initials: F
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China. flyingwangnan@126.com.|Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China. flyingwangnan@126.com.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China. flyingwangnan@126.com.
authors.forename: Nannan
authors.initials: N
authors.lastname: Wang
mesh_terms: D048230:Corynebacterium glutamicum / Q000235:genetics*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D060847:Metabolic Engineering; D010957:Plasmids; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D050644:Succinate-Semialdehyde Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*
chemical_list: D026901:Membrane Transport Proteins; D011994:Recombinant Proteins; D005680:gamma-Aminobutyric Acid; D050644:Succinate-Semialdehyde Dehydrogenase
keywords: Corynebacterium glutamicum; GABA decomposition; gabP; gabT; γ-Aminobutyric acid