title: Disruption of pknG enhances production of gamma-aminobutyric acid by Corynebacterium glutamicum expressing glutamate decarboxylase.
abstract: Gamma-aminobutyric acid (GABA), a building block of the biodegradable plastic polyamide 4, is synthesized from glucose by Corynebacterium glutamicum that expresses Escherichia coli glutamate decarboxylase (GAD) B encoded by gadB. This strain was engineered to produce GABA more efficiently from biomass-derived sugars. To enhance GABA production further by increasing the intracellular concentration of its precursor glutamate, we focused on engineering pknG (encoding serine/threonine protein kinase G), which controls the activity of 2-oxoglutarate dehydrogenase (Odh) in the tricarboxylic acid cycle branch point leading to glutamate synthesis. We succeeded in expressing GadB in a C. glutamicum strain harboring a deletion of pknG. C. glutamicum strains GAD and GAD ∆pknG were cultured in GP2 medium containing 100 g L(-1) glucose and 0.1 mM pyridoxal 5'-phosphate. Strain GAD∆pknG produced 31.1 ± 0.41 g L(-1) (0.259 g L(-1) h(-1)) of GABA in 120 hours, representing a 2.29-fold higher level compared with GAD. The production yield of GABA from glucose by GAD∆pknG reached 0.893 mol mol(-1).
authors.affiliation: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe 657-8501, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Okai
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe 657-8501, Japan.
authors.forename: Chihiro
authors.initials: C
authors.lastname: Takahashi
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe 657-8501, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Hatada
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe 657-8501, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ogino
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe 657-8501, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
keywords: 2-oxoglutarate dehydrogenase; Corynebacterium glutamicum; Gamma-aminobutyric acid; Glutamate decarboxylase; Protein kinase G