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Time course of extracellular GABA production byC. glutamicumGAD, and GAD∆pknGfrom 100 g L−1glucose.C. glutamicum strains GAD, and GAD∆pknG were cultured separately in 20 mL of GP2 medium containing 100 g L−1 glucose and 25 μg mL−1 kanamycin in 200-mL baffled flasks. Fermentation was performed at 30°C for 168 hours at 120 rpm. A: Extracellular GABA concentrations (closed symbols) and glucose concentrations (open symbols) of C. glutamicum strains GAD (squares) and GAD∆pknG (circles ) were monitored. B: Extracellular glutamate concentrations (open symbols) and the OD600 (closed symbols) of the C. glutamicum strains GAD (squares), and GAD∆pknG (circles) were monitored throughout the fermentation. Data are expressed as the mean and standard error from three independent experiments.
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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 furt...
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... determine the yield of GABA, fermentation was performed using strains GAD and GADΔpknG. The strains were cultivated in BHI medium at 30°C for 24 hours, and 5% (w/v) of the starter-culture solution was transferred to a 200 mL baffled flask containing 20 mL GP2 medium with 100 g L −1 glucose and 25 μg mL −1 kanamycin, and agitated at 120 rpm for 168 hours (Figure 3). ...Context 2
... evaluate GABA production, strains GAD, and GA DΔpknG were separately cultivated in GP2 medium containing 100 g L −1 of glucose using baffled flasks (Figure 3). As glucose in the GP2 medium consistently decreased from the beginning of the fermentation, the concentration of extracellular GABA produced by C. glutamicum GADΔpknG simultaneously increased, reach- ing a maximum level of 31.16 ± 0.41 g L −1 after 120 hours ( Figure 3A). ...Context 3
... evaluate GABA production, strains GAD, and GA DΔpknG were separately cultivated in GP2 medium containing 100 g L −1 of glucose using baffled flasks (Figure 3). As glucose in the GP2 medium consistently decreased from the beginning of the fermentation, the concentration of extracellular GABA produced by C. glutamicum GADΔpknG simultaneously increased, reach- ing a maximum level of 31.16 ± 0.41 g L −1 after 120 hours ( Figure 3A). The rate of GABA production by C. glutami- cum GADΔpknG reached 0.259 (g L −1 h −1 ). ...Context 4
... 60.90 ± 4.89 g L −1 of glucose was consumed by GADΔpknG in 120 hours, the molar yield of GABA from glucose reached 0.893 mol mol −1 (Table 3). At the same time, strain GAD produced 13.06 ± 0.45 g L −1 of GABA in 120 hours, consuming 83.62 ± 2.92 g L −1 of glucose ( Figure 3A, Table 3), The glucose consumption rate of strain GADΔpknG was lower than that of strain GAD ( Figure 3A). The molar yield of GABA from glucose by strain GAD was 0.272 mol mol −1 in 120 hours. ...Context 5
... 60.90 ± 4.89 g L −1 of glucose was consumed by GADΔpknG in 120 hours, the molar yield of GABA from glucose reached 0.893 mol mol −1 (Table 3). At the same time, strain GAD produced 13.06 ± 0.45 g L −1 of GABA in 120 hours, consuming 83.62 ± 2.92 g L −1 of glucose ( Figure 3A, Table 3), The glucose consumption rate of strain GADΔpknG was lower than that of strain GAD ( Figure 3A). The molar yield of GABA from glucose by strain GAD was 0.272 mol mol −1 in 120 hours. ...Context 6
... growth rate of strain GADΔpknG was lower than that of strain GAD. Extracellular L-glutamate was not produced by either strain GAD or GADΔpknG using these fermentation conditions ( Figure 3B). ...Context 7
... a pknG-deficient strain was constructed to reduce the metabolic flux to the TCA cycle. We show here that the yield of GABA in cultures of strain GADΔpknG was 2.29-fold higher in 120 hours compared with that of strain GAD (Figure 3, Table 3), suggesting that the pknG deletion influenced ODHC activity by causing an increase in the intracellular glutamate level that enhanced GABA production. We assumed that the ODHC activity of strain GADΔpknG was reduced, because OdhI was not phosphorylated and could not activate the ODHC complex, which caused an increase in carbon flux into the glutamate pathway compared with that of strain GAD. ...Context 8
... assumed that the ODHC activity of strain GADΔpknG was reduced, because OdhI was not phosphorylated and could not activate the ODHC complex, which caused an increase in carbon flux into the glutamate pathway compared with that of strain GAD. The glucose consumption rate and growth rate of GADΔpknG was lower than that of GAD (Figure 3, Table 3), suggesting that the flux to TCA cycle was decreased. We plan to analyze carbon flux of these strains in the future. ...Context 9
... plan to analyze carbon flux of these strains in the future. Moreover, in the late stage of fermentation, reduction of GABA production was observed in cultures of strain GADΔpknG ( Figure 3A). Because reduced levels of the product were also observed in cultures of strain GAD ( Takahashi et al. 2012), we are now attempting to disrupt the genes for GABA assimilation. ...Context 10
... L −1 of GABA was directly produced from glucose without addition of a nitrogen or carbon source during the fermen- tation. Notably, because our GP2 medium contains biotin to support growth, glutamate is not secreted ( Figures 3B and 4). A one-step production system has long been a goal for producing precursors for synthesizing bulk chemicals, and we show here that this was possible for robust produc- tion of GABA using GADΔpknG. ...Similar publications
The bacterium Corynebacterium glutamicum is utilized during industrial fermentation to produce amino acids such as l-glutamate. During l-glutamate fermentation, C. glutamicum changes the flux of central carbon metabolism to favor l-glutamate production, but the molecular mechanisms that explain these flux changes remain largely unknown. Here, we fo...
Citations
... Co-expression of gadB2 and mutant gadB1 under the optimized promoter and RBS combination in C. glutamicum SH facilitated 25 g/L GABA (Shi et al. 2018). The overexpression of GadB derived from E. coli facilitated 31 g/L of GABA in batch culture (Okai et al. 2014;Takahashi et al. 2012). The expression of E. coli GadB mutant (Glu89Gln, Δ452-466, with expanding active pH range) (Thu Ho et al. 2013) under PH36 promoter resulted 38.6 g/L GABA with the productivity of 0.536 g/L/h (Choi et al. 2015). ...
... Disruption of the biosynthesis pathways of by-products is also functional for GABA improvement. Deletion of pknG in C. glutamicum (GAD) promoted 31.1 g/L (0.259 g/L/h, 0.893 mol/mol) of GABA after 120 h fermentation, resulting a 2.29-fold GABA improvement (Okai et al. 2014). PknG catalyzes the phosphorylation of OdhI (Fig. 2), and the dephosphorylation of OdhI could bind to E1 subunit of ketoglutarate dehydrogenase complex (ODHC) to inhibit the activity of ODHC (Schultz et al. 2007). ...
Gamma-aminobutyric acid (GABA) is a non-protein amino acid which is widely applied in agriculture and pharmaceutical additive industries. GABA is synthesized from glutamate through irreversible α-decarboxylation by glutamate decarboxylase. Recently, microbial synthesis has become an inevitable trend to produce GABA due to its sustainable characteristics. Therefore, reasonable microbial platform design and metabolic engineering strategies for improving production of GABA are arousing a considerable attraction. The strategies concentrate on microbial platform optimization, fermentation process optimization, rational metabolic engineering as key metabolic pathway modification, promoter optimization, site-directed mutagenesis, modular transporter engineering, and dynamic switch systems application. In this review, the microbial producers for GABA were summarized, including lactic acid bacteria, Corynebacterium glutamicum, and Escherichia coli, as well as the efficient strategies for optimizing them to improve the production of GABA.
... Expression of gad gene has been associated with higher antibiotic resistance in Escherichia coli (Adam et al. 2008). PknG has also been shown to regulate GABA production (Okai et al. 2014), suggesting a link between Gad, acid resistance and antibiotic resistance (Nguyen 2005a, Nguyen et al. 2005b. Mtb genome codes for gad (Camus et al. 2002, Cole et al. 1998) and our preliminary data confirm mRNA expression and enzymatic activity in Mtb cells during normal growth, in acidic medium and during infection in macrophages, suggesting the indispensable nature of the enzyme (our unpublished data). ...
Given the emergence and spread of multidrug-resistant and extensively drug-resistant strains of Mycobacterium tuberculosis (Mtb), the world faces the urgency of new drugs to combat tuberculosis (TB). Understanding the biochemical/physiological processes enabling Mtb to survive the stressful environment within macrophages and acquire tolerance, resistance and persistence against the stresses are the key to developing new approaches to tackle this health problem. As Mtb gains entry into the respiratory tract and is engulfed by macrophages, lowering pH acts as a primary defence of phagosomes within macrophages and also in the centres of caseating granulomas. It becomes essential for the pathogen to maintain pH homeostasis for survival in these conditions. Acid resistance mechanisms are well known and extensively studied in other bacteria such as Escherichia coli, Lactobacillus spp., Brucella spp., Helicobacter pylori and Listeria monocytogenes. However, in the case of Mtb, acid tolerance and resistance mechanisms still need to be explored in detail. This review targets to provide the current understanding of underlying mechanisms involved in countering low pH faced by Mtb as the acid resistance/tolerance mechanisms contribute to the pathogenesis of the disease.
... Mostly, GADs used for enzymatic conversion or wholecell conversion of MSG into GABA have shown specific activity under acidic conditions. Particularly, GADs from Lactobacillus zymae, 23 E. coli, 24 Lactobacillus sakei A156, 25 and L. brevis HYE1 26 were reported to be only active at pH 4.0− 5.0. Given that the optimal pH for cell growth is higher than that for optimal GAD activity, these GADs cannot be used in direct fermentative GABA production from renewable resources, as they are unable to support the efficient production of GABA during the exponential growth phase of the host strain. ...
... Moreover, GAD is active during the stationary phase when both pH and cell growth have begun to significantly decrease, which ultimately results in retarded productivity of GABA requiring long cultivation times of over 120 h. 24,27 Therefore, the employment of various GADs exhibiting enhanced activity within a wider pH range (pH 5.0−7.0) has been attempted to produce high GABA yields in a growthassociated manner. ...
γ-Aminobutyrate (GABA) is an important chemical by itself and can be further used for the production of monomer used for the synthesis of biodegradable polyamides. Until now, GABA production usingCorynebacterium glutamicum harboring glutamate decarboxylases (GADs) has been limited due to the discrepancy between optimal pH for GAD activity (pH 4.0) and cell growth (pH 7.0). In this study, we developed recombinant C. glutamicum strains expressing mutated GAD from Escherichia coli (EcGADmut) and GADs from Lactococcus lactis CICC20209 (LlGAD) and Lactobacillus senmaizukei (LsGAD), all of which showed enhanced pH stability and adaptability at a pH of approximately 7.0. In shake flask cultivations, the GABA productions of C. glutamicum H36EcGADmut, C. glutamicum H36LsGAD, and C. glutamicum H36LlGAD were examined at pH 5.0, 6.0, and 7.0, respectively. Finally, C. glutamicum H36EcGADmut (40.3 and 39.3 g L-1), H36LlGAD (42.5 and 41.1 g L-1), and H36LsGAD (41.6 and 40.2 g L-1) produced improved GABA titers and yields in batch fermentation at pH 6.0 and pH 7.0, respectively, from 100 g L-1 glucose. The recombinant strains developed in this study could be used for the establishment of sustainable direct fermentative GABA production from renewable resources under mild culture conditions, thus increasing the availability of various GADs.
... Genetic modifications of the metabolic network increased the carbon flux toward the GABA biosynthetic pathway. The reduction in α-ketoglutarate dehydrogenase (EC 1.2.4.2) activity by deleting pknG or odhA genes increased the supply of L-glutamate for GABA biosynthesis, and the inhibition of α-ketoglutarate dehydrogenase activity by increasing its inhibitory protein OdhI also improved putrescine-based GABA production [31,35,36]. The overexpression of PEP carboxylase (EC 4.1.1.31) ...
... AKGDH is composed of three subunits encoded by odhA, sucB, and lpdA genes, and its activity is regulated by PknG and OdhI [67]. Metabolic engineering strategies focused on reducing the α-ketoglutarate dehydrogenase activity by deleting odhA/pknG or overexpressing odhI genes for GABA production [31,35]. Unlike previous reports, we first pushed more carbon flux toward α-ketoglutarate synthesis by increasing the expression of acn and icd genes, and then redirected α-ketoglutarate toward GABA synthesis by deleting the sucCD gene rather than inhibiting AKGDH activity. ...
... In addition, no elevated overflow of flux in response to sucCD deletion in C. glutamicum indicated that the TCA cycle could normally operate as the inactivation of succinyl-CoA synthetase [60]. Other reported strategies for TCA cycle modification by deleting pknG or odhA, deleting mdh, and overexpressing ppc had a positive effect on GABA biosynthesis via the GAD-based route, and GABA production improved to 31.1 g/L, 29.5 g/L, and 26.3 g/L, respectively [31,35,37]. The GABA-6 strain shows a similar potential for GABA production, demonstrating the effectiveness of genetic modification of the TCA cycle in this study. ...
Gamma-aminobutyric acid (GABA) can be used as a bioactive component in the pharmaceutical industry and a precursor for the synthesis of butyrolactam, which functions as a monomer for the synthesis of polyamide 4 (nylon 4) with improved thermal stability and high biodegradability. The bio-based fermentation production of chemicals using microbes as a cell factory provides an alternative to replace petrochemical-based processes. Here, we performed model-guided metabolic engineering of Corynebacterium glutamicum for GABA and butyrolactam fermentation. A GABA biosynthetic pathway was constructed using a bi-cistronic expression cassette containing mutant glutamate decarboxylase. An in silico simulation showed that the increase in the flux from acetyl-CoA to α-ketoglutarate and the decrease in the flux from α-ketoglutarate to succinate drove more flux toward GABA biosynthesis. The TCA cycle was reconstructed by increasing the expression of acn and icd genes and deleting the sucCD gene. Blocking GABA catabolism and rewiring the transport system of GABA further improved GABA production. An acetyl-CoA-dependent pathway for in vivo butyrolactam biosynthesis was constructed by overexpressing act-encoding ß-alanine CoA transferase. In fed-batch fermentation, the engineered strains produced 23.07 g/L of GABA with a yield of 0.52 mol/mol from glucose and 4.58 g/L of butyrolactam. The metabolic engineering strategies can be used for genetic modification of industrial strains to produce target chemicals from α-ketoglutarate as a precursor, and the engineered strains will be useful to synthesize the bio-based monomer of polyamide 4 from renewable resources.
... In fed-batch cultures, 70.6 g/L of GABA were accumulated using glucose after 70 h via a two-stage pH control. Increase of intracellular pool of L-glutamate for GABA production was attained by deletion of pknG encoding serine/threonine protein kinase (Okai et al., 2014), overexpression of ppc or deletion of mdh (Shi et al., 2017), or deletion of NCgl1221 encoding L-glutamate exporter (Cho et al., 2017). Another approach to enhance GABA production was conducted by secretion of GAD enzyme and blocking GABA import and degradation ( gapP gapT), whereby extracellular accumulated L-glutamate was directly converted to GABA (Wen and Bao, 2021). ...
Corynebacterium glutamicum is used for the million-ton-scale production of amino acids. Valorization of sidestreams from agri- and aqua-culture has focused on the production of biofuels and carboxylic acids. Nitrogen present in various amounts in sidestreams may be valuable for the production of amines, amino acids and other nitrogenous compounds. Metabolic engineering of C. glutamicum for valorization of agri- and aqua-culture sidestreams addresses to bridge this gap. The product portfolio accessible via C. glutamicum fermentation primarily features amino acids and diamines for large-volume markets in addition to various specialty amines. On the one hand, this review covers metabolic engineering of C. glutamicum to efficiently utilize components of various sidestreams. On the other hand, examples of the design and implementation of synthetic pathways not present in native metabolism to produce sought after nitrogenous compounds will be provided. Perspectives and challenges of this concept will be discussed.
... These metabolic pathways generated two genetic modification strategies for GABA production in C. glutamicum. The first strategy is the heterologous expression of gad from E. coli [7,22,127] or Lactobacillus brevis [155,156,182]. For instance, recombinant strains harboring E. coli GadB were constructed under the strong promoter H36 that produced 5.89 ± 0.35 g/L of GABA, which represents a breakthrough from nothing [22]. ...
l-glutamate family amino acids (GFAAs), consisting of l-glutamate, l-arginine, l-citrulline, l-ornithine, l-proline, l-hydroxyproline, γ-aminobutyric acid, and 5-aminolevulinic acid, are widely applied in the food, pharmaceutical, cosmetic, and animal feed industries, accounting for billions of dollars of market activity. These GFAAs have many functions, including being protein constituents, maintaining the urea cycle, and providing precursors for the biosynthesis of pharmaceuticals. Currently, the production of GFAAs mainly depends on microbial fermentation using Corynebacterium glutamicum (including its related subspecies Corynebacterium crenatum), which is substantially engineered through multistep metabolic engineering strategies. This review systematically summarizes recent advances in the metabolic pathways, regulatory mechanisms, and metabolic engineering strategies for GFAA accumulation in C. glutamicum and C. crenatum, which provides insights into the recent progress in l-glutamate-derived chemical production.
... Man et al. applied a variant RBS to reduce the ODHC activity to transfer carbon flux into the L-arginine pathway, but found that the cell growth and glucose consumption decreased with the reduction of ODHC activity (Man et al., 2016). Okai et al. had demonstrated that disruption of pknG, which encoded serine/threonine protein kinase G to control the ODHC activity, could enhance the production of GABA in C. glutamicum, and the obvious growth retardation was observed (Okai et al., 2014). In addition, Nguyen et al. also tried to reduce the ODHC activity by replacing the translational start codon of odhA with TTG and mutated OdhI T15A (spermidine N-acetyltransferase) to increase the production of putrescine, whereas the growth was hardly decreased (Nguyen et al., 2015). ...
Synthetic biology seeks to reprogram microbial cells for efficient production of value-added compounds from low-cost renewable substrates. A great challenge of chemicals biosynthesis is the competition between cell metabolism and target product synthesis for limited cellular resource. Dynamic regulation provides an effective strategy for fine-tuning metabolic flux to maximize chemicals production. In this work, we created a tunable growth phase-dependent autonomous bifunctional genetic switch (GABS) by coupling growth phase responsive promoters and degrons to dynamically redirect the carbon flux for metabolic state switching from cell growth mode to production mode, and achieved high-level GABA production from low-value glycerol in Corynebacterium glutamicum. A ribosome binding sites (RBS)-library-based pathway optimization strategy was firstly developed to reconstruct and optimize the glycerol utilization pathway in C. glutamicum, and the resulting strain CgGly2 displayed excellent glycerol utilization ability. Then, the initial GABA-producing strain was constructed by deleting the GABA degradation pathway and introducing an exogenous GABA synthetic pathway, which led to 5.26 g/L of GABA production from glycerol. In order to resolve the conflicts of carbon flux between cell growth and GABA production, we used the GABS to reconstruct the GABA synthetic metabolic network, in which the competitive modules of GABA biosynthesis, including the tricarboxylic acid (TCA) cycle module and the arginine biosynthesis module, were dynamically down-regulated while the synthetic modules were dynamically up-regulated after sufficient biomass accumulation. Finally, the resulting strain G7-1 accumulated 45.6 g/L of GABA with a yield of 0.4 g/g glycerol, which was the highest titer of GABA ever reported from low-value glycerol. Therefore, these results provide a promising technology to dynamically balance the metabolic flux for the efficient production of other high value-added chemicals from a low-value substrate in C. glutamicum.
... The gene ldh was deleted from CGY700, resulting in the strain CGY705, and the GABA production in CGY705 reached 22.40 g/L after 60 h fermentation (Fig. 2b), which is 17.0% increase compared to the starting strain CGY700 (19.14 g/L). Serine/threonine protein kinase G (PknG) could phosphorylate OdhI, the dephosphorylated ODhI can binds to E1 subunit of 2-oxoglutarate dehydrogenase complex (ODHC) and inhibit its activity [32], therefore, ΔpknG mutant could improve the GABA production in C. glutamicum [33,34]. The pknG was deleted from CGY700, resulting in the strain CGY707. ...
Gamma-aminobutyric acid is an important nonprotein amino acid and has been extensively applied in pharmaceuticals, livestock, food additives, and so on. It is important to develop Corynebacterium glutamicum strains that can efficiently produce gamma-aminobutyric acid from glucose. In this study, production of gamma-aminobutyric acid in C. glutamicum CGY700 was improved by construction of CO2 anaplerotic reaction and overexpression of citrate synthase. The co-expression of ppc encoding phosphoenolpyruvate carboxylase and gltA encoding citrate synthase was constructed and optimized in the chromosome to compensate carbon loss and conquer metabolic bottleneck. The expression of ppc and gltA were controlled by promoters Ptac and PtacM, and the optimal mode of PtacM-ppc-Ptac-gltA was determined. Simultaneously, the genes pknG encoding serine/threonine protein kinase G and ldh encoding l-lactate dehydrogenase were deleted, and glnA2 encoding glutamine synthase was overexpressed in the chromosome. The final strain CGY-PG-304 constructed in this study could produce 41.17 g/L gamma-aminobutyric acid in shake flask cultivation and 58.33 g/L gamma-aminobutyric acid via Fed-Batch fermentation with a yield of 0.30 g/g glucose. CGY-PG-304 was constructed by genome editing; therefore, it is stable and not necessary to add any antibiotics and inducer during fermentation.
... Fermentative production of GABA from glucose has also been achieved by engineering Corynebacterium glutamicum, a major L-glutamate-producing organism, and thus resulting in high titers (Choi et al. 2015;Okai et al. 2014;Shi et al. 2013;Takahashi et al. 2012;Wang et al. 2015). Takahashi et al. achieved a titer of 12.37 ± 0.88 g/L using the recombinant C. glutamicum strain GAD (expressing a glutamate decarboxylase encoded by the gadB gene of E. coli W3110) (Takahashi et al. 2012). ...
... Takahashi et al. achieved a titer of 12.37 ± 0.88 g/L using the recombinant C. glutamicum strain GAD (expressing a glutamate decarboxylase encoded by the gadB gene of E. coli W3110) (Takahashi et al. 2012). GABA production was further enhanced by Okai et al. through increasing the flux of 2-oxoglutarate toward glutamate, via the deletion of pknG (encoding serine/threonine protein kinase G) that resulted in the production of 31.1 ± 0.41 g GABA/L (0.893 mol/mol glucose and 0.259 g/L/h) (Okai et al. 2014). Choi et al. developed recombinant C. glutamicum strains by expressing an alternative E. coli glutamate decarboxylase mutant that is active across an expanded pH range. ...
Lactams, cyclic carboxamide acids, are important building blocks as monomers for the manufacture of polyamides (nylons), with a market of millions of tons per year. Likewise, their non-natural building blocks, straight chain ω-amino acids, also have a wide range of applications as pharmaceuticals, therapeutic agents, and precursors to other platform chemicals. Current industrial lactam production requires petrochemically-derived routes that involve the use of harsh chemicals and reaction conditions. Microbial production provides a more sustainable method for production, from cost effective renewable resources. This review provides an extensive overview of progress toward the microbial production of lactams, particularly 4C butyrolactam, 5C valerolactam and 6C caprolactam, and their ω-amino acid precursors. Additionally, recent advances in the field as well as proposed microbial production pathways will be discussed, as well as future perspectives for the production of these important bulk chemicals.
... (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) decarboxylase gabB from either Lactobacillus brevis (Shi and Li, 2011) or E. coli (Okai et al., 2014;Takahashi et al., 2012). Coexpression of the two alleles gabB1 and gabB2 combined with an optimized urea supply improved the production to 26 g L −1 after 60 h of fed-batch fermentation (Shi et al., 2013a). ...
... Coexpression of the two alleles gabB1 and gabB2 combined with an optimized urea supply improved the production to 26 g L −1 after 60 h of fed-batch fermentation (Shi et al., 2013a). Increased supply of the GABA precursor L-glutamate was achieved by deleting the pknG gene encoding serine/ threonine protein kinase G (Okai et al., 2014), which controls the activity of the 2-oxoglutarate dehydrogenase complex (ODHC) (Niebisch et al., 2006), a key enzyme in L-glutamate production (Asakura et al., 2007;Kim et al., 2009). Upon pknG deletion, GABA production was increased by 2.3-fold (Okai et al., 2014). ...
... Increased supply of the GABA precursor L-glutamate was achieved by deleting the pknG gene encoding serine/ threonine protein kinase G (Okai et al., 2014), which controls the activity of the 2-oxoglutarate dehydrogenase complex (ODHC) (Niebisch et al., 2006), a key enzyme in L-glutamate production (Asakura et al., 2007;Kim et al., 2009). Upon pknG deletion, GABA production was increased by 2.3-fold (Okai et al., 2014). Similarly, direct deletion of odhA, encoding a subunit of ODHC, improved GABA production . ...
Corynebacterium glutamicum is a major workhorse in industrial biotechnology for 60 years. As the world's flagship for amino acids, the microbe produces l‐glutamate and l‐lysine at a scale of seven million tons per year. In addition, it has been upgraded into a most versatile cell factory and meanwhile provides more than 80 different natural and non‐natural compounds for chemical, energy, food and feed, cosmetic, pharmaceutical, and medical applications. In this chapter, we introduce this well‐performing bacterium and highlight pioneering discoveries as well as milestones in technology and application. Moreover, we summarize recent advances to streamline C. glutamicum for novel types of products and valorization of newly arising sustainable feedstocks.
