Gamma-aminobutyric Acid Production Research Articles

Continuous production of gamma aminobutyric acid by engineered and immobilized Escherichia coli whole-cells in a small-scale reactor system

γ-Amino butyric acid (GABA) is a non-proteinogenic amino acid and a human neurotransmitter. Recently, increasing demand for food additives and biodegradable bioplastic monomers, such as nylon 4, has been reported. Consequently, considerable efforts have been made to produce GABA through fermentation and bioconversion. To realize bioconversion, wild-type or recombinant strains harboring glutamate decarboxylase were paired with the cheap starting material monosodium glutamate, resulting in less by-product formation and faster production compared to fermentation. To increase the reusability and stability of whole-cell production systems, this study used an immobilization and continuous production system with a small-scale continuous reactor for gram-scale production. The cation type, alginate concentration, barium concentration, and whole-cell concentration in the beads were optimized and this optimization resulted in more than 95 % conversion of 600 mM monosodium glutamate to GABA in 3 h and reuse of the immobilized cells 15 times, whereas free cells lost all activity after the ninth reaction. When a continuous production system was applied after optimizing the buffer concentration, substrate concentration, and flow rate, 165 g of GABA was produced after 96 h of continuous operation in a 14-mL scale reactor. Our work demonstrates the efficient and economical production of GABA by immobilization and continuous production in a small-scale reactor.

Preparation of magnetic polyacrylamide hydrogel with chitosan for immobilization of glutamate decarboxylase to produce γ-aminobutyric acid

Gamma-aminobutyric acid (GABA) is an vital neurotransmitter, and the reaction to obtain GABA through biocatalysis requires coenzymes, which are therefore limited in the production of GABA. In this study, polyacrylamide hydrogels doped with chitosan and waste toner were synthesized for glutamate decarboxylase (GAD) and coenzyme co-immobilization to realize the production of GABA and the recovery of coenzymes. Enzymatic properties of immobilized GAD were discussed. The immobilized enzymes have significantly improved pH and temperature tolerance compared to free enzymes. In terms of reusability, after 10 repeated reuses of the immobilized GAD, the residual enzyme activity of immobilized GAD still retains 100% of the initial enzyme activity, and the immobilized coenzyme can also be kept at about 32%, with better stability and reusability. And under the control of no exogenous pH, immobilized GAD showed good performance in producing GABA. Therefore, in many ways, the new composite hydrogel provides another way for the utilization of waste toner and promises the possibility of industrial production of GABA.

Genome sequences and functional analysis of Levilactobacillus brevis LSF9-1 and Pediococcus acidilactici LSF1-1 from fermented fish cake (Som-fak) with gamma-aminobutyric acid (GABA) production.

Gamma-aminobutyric acid (GABA) is a crucial inhibitory neurotransmitter in the sympathetic nervous system that exerts regulatory effects on the blood, immune, and nervous systems. GABA production in som-fak, a traditional fermented fish of Thailand, has been attributed to the activity of lactic acid bacteria (LAB). The present study aims to characterize the LAB isolates and compare the genomes and GABA synthesis genes of selected isolates capable of GABA production. Thirteen isolates demonstrating GABA synthesis capability were identified based on their phenotypic and genotypic characteristics. Seven isolates (group I: LSF3-3, LSF8-3, LSF9-1, LSF9-3, LSF9-6, LSF9-7, and LSF10-14) were identified as Levilactobacillus brevis with 99.78-100% similarity. LSF2-1, LSF3-2, LSF5-4, and LSF6-5 (group II) were identified as Lactiplantibacillus pentosus with 99.86-100% similarity. Strain LSF1-1 (group III) was identified as Pediococcus acidilactici (99.47%), and LSF10-4 (group IV) was identified as Pediococcus pentosaceus with 99.93% similarity. The GABA production of isolates ranged from 0.087 to 16.935g/L. The maximum production of 16.935g/L from 3% monosodium glutamate was obtained from strain LSF9-1. Gene and genome analysis revealed that L. brevis LSF9-1 has multiple gad genes in the genome, such as gadB1, gadB2, gadC1, and gadC2, making it the potential strain for GABA production. Additionally, the genome analysis of P. acidilactici LSF1-1 consists of gadA, gadB, and gadC, which respond to controlling GABA production and export. Furthermore, strain LSF1-1 was considered safe, containing no virulence factors. Thus, Levilactobacillus brevis LSF9-1 and Pediococcus acidilactici LSF1-1 have the potential for GABA production and probiotic use in future studies.

Biosynthesis of Gamma-Aminobutyric Acid by Engineered Clostridium tyrobutyricum Co-Overexpressing Glutamate Decarboxylase and Class I Heat Shock Protein

Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the mammalian central nervous system that has a significant beneficial effect on human health. Traditional microbial GABA synthesis requires continuous oxygen supplementation. Here, a new anaerobic platform for GABA production was established with engineered C. tyrobutyricum ATCC 25755, which is considered an ideal anaerobic microbial-cell factory for bioproduction. Glutamate decarboxylase (GAD) and Class I heat-shock proteins were screened and overexpressed, generating an excellent Ct-pMAG strain for monosodium-glutamate (MSG) tolerance and GABA production, with a GABA titer of 14.26 g/L in serum bottles with the mixed substrate of glucose and MSG. Fed-batch fermentation was carried out in a 5 L bioreactor, achieving 35.57 g/L and 122.34 g/L final titers of GABA by applying the pH-free strategy and the pH-control strategy, respectively using MSG. Finally, a two-stage strategy (growth stage and bioconversion stage) was applied using glutamate acid (L-Glu) and glucose as the substrate, obtaining a 400.32 g/L final titer of GABA with a productivity of 36.39 g/L/h. Overall, this study provides an anaerobic-fermentation platform for high-level bio-GABA production.

Sodium-Ion-Free Fermentative Production of GABA with Levilactobacillus brevis CD0817

Gamma-aminobutyric acid (GABA) has positive effects on many physiological processes. Lactic acid bacterial production of GABA is a future trend. This study aimed to produce a sodium-ion-free GABA fermentation process for Levilactobacillus brevis CD0817. In this fermentation, both the seed and fermentation media used L-glutamic acid instead of monosodium L-glutamate as the substrate. We optimized the key factors influencing GABA formation, adopting Erlenmeyer flask fermentation. The optimized values of the key factors of glucose, yeast extract, Tween 80, manganese ion, and fermentation temperature were 10 g/L, 35 g/L, 1.5 g/L, 0.2 mM, and 30 °C, respectively. Based on the optimized data, a sodium-ion-free GABA fermentation process was developed using a 10-L fermenter. During the fermentation, L-glutamic acid powder was continuously dissolved to supply substrate and to provide the acidic environment essential for GABA synthesis. The current bioprocess accumulated GABA at up to 331 ± 8.3 g/L after 48 h. The productivity of GABA was 6.9 g/L/h and the molar conversion rate of the substrate was 98.1%. These findings demonstrate that the proposed method is promising in the fermentative preparation of GABA by lactic acid bacteria.

Whole-Genome Sequence of Lactococcus lactis Subsp. lactis LL16 Confirms Safety, Probiotic Potential, and Reveals Functional Traits.

Safety is the most important criteria of any substance or microorganism applied in the food industry. The whole-genome sequencing (WGS) of an indigenous dairy isolate LL16 confirmed it to be Lactococcus lactis subsp. lactis with genome size 2,589,406 bp, 35.4% GC content, 246 subsystems, and 1 plasmid (repUS4). The Nextera XT library preparation kit was used to generate the DNA libraries, and the sequencing was carried out on an Illumina MiSeq platform. In silico analysis of L. lactis LL16 strain revealed non-pathogenicity and the absence of genes involved in transferable antimicrobial resistances, virulence, and formation of biogenic amines. One region in the L. lactis LL16 genome was identified as type III polyketide synthases (T3PKS) to produce putative bacteriocins lactococcin B, and enterolysin A. The probiotic and functional potential of L. lactis LL16 was investigated by the presence of genes involved in adhesion and colonization of the host's intestines and tolerance to acid and bile, production of enzymes, amino acids, and B-group vitamins. Genes encoding the production of neurotransmitters serotonin and gamma-aminobutyric acid (GABA) were detected; however, L. lactis LL16 was able to produce only GABA during milk fermentation. These findings demonstrate a variety of positive features that support the use of L. lactis LL16 in the dairy sector as a functional strain with probiotic and GABA-producing properties.

Effect of soaking conditions on gamma-aminobutyric acid (GABA) and amino acids content in mung bean

Gamma-aminobutyric acid (GABA) offers numerous beneficial effects on human health, especially as blood pressure regulator and stress control. This functional compound is usually found in grains including mung bean. Mung bean (Vigna radiate) is one of the famous grains in Southeast Asia and is usually used in cooking as porridge or dessert by local people. It is highly nutritious with protein and antioxidants. In this study, the optimum soaking conditions were determined to enhance GABA content in mung beans. An RSM with a five-level, three-factorial, Central composite Rotatable Design (CCRD) was used to determine the soaking parameters to obtain maximum GABA content, essential amino acid (EAA) and total amino acids (TAA) in mung bean. The factors that were included in the RSM analysis were temperature, time and weight of beans to water ratio. GABA and amino acids were determined by using UPLC. The optimum condition for significant GABA production (p<0.05) was determined as 40°C, 4 hrs and 1:5 of temperature, time and soaking water level, respectively with the highest GABA content quantified as 130.12 mg/100 g dry weight (DW). Model optimization and validation were done according to the optimum conditions from the RSM analysis resulting in 124.17 mg/100 g DW of GABA, closer to the predicted value (130.07 mg/100 g DW). The optimum conditions determined by RSM could be beneficial to the industry, especially functional food production to cater for the demand for health-promoting products in the market.

Development and properties evaluation of multi-strain probiotic with cholesterol-lowering potential in vitro.

Probiotics have a cholesterol-lowering effect. Multi-strain probiotics (MSPs) outperformed single-strain probiotics due to the interaction of strains. Hence, we expect to develop a high-efficiency MSP for lowering cholesterol. Three strains, including Lactobacillus caseiS1, Enterococcus faeciumS4, and L. harbinensisS6, were used to develop the MSPs. To evaluate their effect, gastrointestinal tolerance, bile salt hydrolase (BSH) activity, cholesterol-lowering rate, antioxidant ability, gamma-aminobutyric acid (GABA) production, and antibiotic sensitivity were determined. The triple lactic acid bacteria probiotic (TLP) was the most efficient one. After 24h treatment with artificial gastric fluid, 47.88% of TLP survived. TLP exhibited the highest BSH activity (149.40 U·ml-1) and cholesterol-lowering rate (75.05%) in vitro, with co-precipitation reducing the majority of cholesterol. The reducing power and superoxide radical scavenging rate of the cell-free supernatant and the hydroxyl radical scavenging rate in viable cells were 1.52, 85.03%, and 89.66%, respectively, and the GABA production was 0.67mg·ml-1, which enhanced the health benefit effects. By fuzzy mathematical analysis, TLP was the optimal probiotic and was competitive with commercial probiotics. The three strains were susceptible to 13 antibiotics. Therefore, TLP has the potential to develop into a cholesterol-lowering probiotic preparation.

Selection and identification of antibacterial and GABA-producing lactic acid bacteria from Vietnamese fermented meat

This study aimed to screen the lactic acid bacteria (LAB) strain that has high potential in gamma-aminobutyric acid (GABA) production and antibacterial properties, which could be applied in Vietnamese fermented meat (Nem chua) fermentation. These bacterial strains were isolated from commercial Nem chua products and stored in the laboratory. GABA synthesized from 18 strains of LAB in the MRS media adding 3% MSG was qualitative and quantitative analyzed through thin layer chromatography (TLC) and its calibration curve equation, then antibacterial activity and lactic acid production were also tested by acidic titration method, and well diffusion method, respectively. The results showed that all LAB strains synthesized GABA with a concentration from 1.323 - 1.582 mg/mL; however, eight strains were recorded with higher potential, including VL1, XP1, TP1, HC2, CP2, LV2, TX7, and HK 162. These eight strains showed the inhibition zone to Escherichia coli indicator from 4.67 - 11.67 mm. Besides, they are capable of yielding lactic acid from 18.00 - 19.35 g/L after seven days of fermentation in MRS media. The strain VL1 with the highest potential was identified as Lactobacillus plantarum. This strain was suggested as a promising starter to be applied in the Nem chua fermentation process.

Optimization of process parameters for GABA and L-DOPA production on fermented coconut drink

Gamma-aminobutyric acid (GABA) and levodopa (L-DOPA) are compounds that can potentially treat hypertension and Parkinson’s diseases. The purpose of this study was to optimize the fermentation parameters for GABA and L-DOPA production by Lactobacillus acidophilus co-cultured with Lactobacillus brevis (LALB) in mature coconut water (MCW). In this study, the response surface methodology (RSM) with central composite design (CCD) was applied to optimize the concentration of sucrose, culture temperature and incubation time. The optimum conditions for the yield of GABA and L-DOPA were found to be: 1 g sucrose at 27oC for 28 hrs of incubation time under static conditions with the predicted accuracy of 95.4% (352 mg GABA/L and 94.7% (89 mg L-DOPA/L). This work was conducted to add value to the by-product of the coconut milk industry through the production of fermented coconut drinks. The MCW fermented with LALB offers a potential functional drink for hypertension and Parkinson’s disease treatment and prevention measures.

Bacillus amyloliquefaciens Increases the GABA in Rice Seed for Upregulation of Type I Collagen in the Skin

Biosynthesis of gamma-aminobutyric acid (GABA) can be achieved by naturally occurring microorganisms with the advantages of cost-effectiveness and safety. In this study, Bacillus amyloliquefaciens EH-9 strain (B. amyloliquefaciens EH-9), a soil bacterium, was used to promote the accumulation of GABA in germinated rice seed. Further, the topical application of supernatant from rice seed co-cultivated with soil B. amyloliquefaciens EH-9 can significantly increase the production of type I collagen (COL1) in the dorsal skin of mice. The knocking down of the GABA-A receptor (GABAA) significantly reduced the production of COL1 in the NIH/3T3 cells and in the dorsal skin of mice. This result suggests that topical application of GABA can promote the biosynthesis of COL1 via its interaction with the GABAA receptor in the dorsal skin of mice. In summary, our findings illustrate for the first time that soil B. amyloliquefaciens EH-9 elicits GABA production in germinated rice seed to upregulate the formation of COL1 in the dorsal skin of mice. This study is translational because the result shows a potential remedy for skin aging by stimulating COL1 synthesis using biosynthetic GABA associated with B. amyloliquefaciens EH-9.

Synbiotic Fermentation of Undaria pinnatifida and Lactobacillus brevis to Produce Prebiotics and Probiotics.

It has been optimized thermal acid hydrolytic pretreatment and enzymatic saccharification (Es) in flask culture of Undaria pinnatifida seaweed, which is a prebiotic. The optimal hydrolytic conditions were a slurry content of 8% (w/v), 180 mM H2SO4, and 121°C for 30 min. Es using Celluclast 1.5 L at 8 U/mL produced 2.7 g/L glucose with an efficiency of 96.2%. The concentration of fucose (a prebiotic) was 0.48 g/L after pretreatment and saccharification. The fucose concentration decreased slightly during fermentation. Monosodium glutamate (MSG) (3%, w/v) and pyridoxal 5'-phosphate (PLP) (30 μM) were added to enhance gamma-aminobutyric acid (GABA) production. To further improve the consumption of mixed monosaccharides, adaptation of Lactobacillus brevis KCL010 to high concentrations of mannitol improved the synbiotic fermentation efficiency of U. pinnatifida hydrolysates.

Optimizing Levilactobacillus brevis NPS-QW 145 Fermentation for Gamma-Aminobutyric Acid (GABA) Production in Soybean Sprout Yogurt-like Product

Gamma-aminobutyric acid (GABA) is a non-protein amino acid with various physiological functions. Levilactobacillus brevis NPS-QW 145 strains active in GABA catabolism and anabolism can be used as a microbial platform for GABA production. Soybean sprouts can be treated as a fermentation substrate for making functional products. This study demonstrated the benefits of using soybean sprouts as a medium to produce GABA by Levilactobacillus brevis NPS-QW 145 when monosodium glutamate (MSG) is the substrate. Based on this method, a GABA yield of up to 2.302 g L-1 was obtained with a soybean germination time of one day and fermentation of 48 h with bacteria using 10 g L-1 glucose according to the response surface methodology. Research revealed a powerful technique for producing GABA by fermentation with Levilactobacillus brevis NPS-QW 145 in foods and is expected to be widely used as a nutritional supplement for consumers.

Evaluation of gamma-aminobutyric acid content in Portuguese cheeses with protected designation of origin status.

Health-conscious consumers are increasingly paying attention to healthy diets and focusing on natural bioactive compounds in foods and their effects on mental health. This opens new opportunities for the study of artisanal cheeses as biofunctional foods. In the work described in this Research Communication, the gamma-aminobutyric acid (GABA) content of seven different Portuguese cheeses produced from unpasteurized cow, sheep, and goat milk and granted with protected designation of origin (PDO) status was analysed. The PDO cheeses made from cow milk analysed in this study were São Jorge (3, 4, 7, 12 and 24 months of maturation) and Pico cheeses. PDO cheeses made from sheep milk were Serra da Estrela, Serpa, Nisa and Azeitão. Cheeses made from sheep and goat milk included Beira Baixa yellow cheese. The GABA content in the Azorean PDO cheeses (made from cow milk) ranged from 1.23 to 2.64 g/kg of cheese. Higher variations in GABA content were observed in cheeses made from sheep and goat milk (0.73-2.31 g/kg). This study provides information on the GABA content in different Portuguese PDO cheeses and shows that hard or semi-hard ripened cheeses are a suitable matrix for GABA production by lactic acid bacteria.

Gamma-aminobutyric acid (GABA) production by potential probiotic strains of indigenous fermented foods origin and RSM based production optimization

The study aimed to evaluate the γ-aminobutyric acid (GABA) producing lactic acid bacterial strains of fermented food origin to be used as potential psychobiotic. A total of 268 isolates were screened for GABA production using the pH indicator method. Five of the isolates were identified as potential GABA producers and were shortlisted further for confirmation of GABA production by NMR and HPLC analysis. One of the strains (G2), identified as Weissella confusa showed the highest production of GABA (246.2 mg/L) while the remaining strains produced only trace amounts. These five strains were assessed for safety and probiotic properties. The strain G2 exhibited the most prominent probiotic properties. It showed good tolerance towards pH(2 and 3), bile salt(0.3–1%), gastro-intestinal fluid, NaCl(1–4%), phenol(0.4–0.6%), auto-aggregation(83%), strong hydrophobicity to xylene(70%) and chloroform(78%), significant antimicrobial activity, susceptibility to antibiotics and strong adherence to Caco-2 cells. From the optimization of culture conditions for GABA production by RSM based approach, G2 was found to produce 293.33 mg/L with a 34h fermentation time, 29.1 °C temperature, and at 1% mono-sodium glutamate concentration. Further studies are needed to assess the efficacy and stability of the isolate in the food matrix and in vivo gut environment, to utilize it as a potential psychobiotic.

Whole-genome analysis of gamma-aminobutyric acid producing Psychobiotic Limosilactobacillus reuteri with its Untargeted metabolomics using UHPLC-Q-Tof MS/MS

The gamma amino butyric acid (GABA) is a chemical messenger and is essential for the health of the brain and muscles. Some lactic acid bacteria (LAB) have the potential to function as psychobiotic cultures because they can produce significant amounts of neuroactive compounds like GABA. Psychobiotics are known to alter bidirectional communication between the gastrointestinal tract and the central nervous system. In the present study, the Limosilactobacillus reuteri (L. reuteri) strain, isolated from human breast milk, was used to detect the GABA-producing glutamic acid decarboxylase (gad) gene and GABA production. PCR, HPLC and UHPLCQ-TOF-MS2 approaches were applied to identify the gad gene, GABA content, and bioactive compounds produced by the bacterial strain, respectively. Additionally, the whole genome was sequenced to better understand the strain's psychobiotic and technological genomic properties. The gadB and gadC genes were confirmed in plasmid 1 of the whole genome. The complete genome sequence of L. reuteri comprises the genome length of 2,087,202 bp with 51.6 percent of G + C content. The results indicate that L. reuteri can be used as a starter culture for the production of GABA-enriched functional foods as well as psychobiotics for health benefits.

Screening of lactic acid bacteria strains isolated from Iranian traditional dairy products for GABA production and optimization by response surface methodology

A total of 50 lactic acid bacteria (LAB) isolates from Iranian traditional dairy products (Motal and Lighvan cheeses, and artisanal yogurt) were screened for gamma-aminobutyric acid (GABA) production. Firstly, a rapid colorimetric test was performed to evaluate the glutamate decarboxylase (GAD) activity among the LAB isolates examined. Thin layer chromatography (TLC) was then performed on selected strains to identify isolates with high/moderate GABA producing capacity, and a GABase micro-titer plate assay was employed to quantify GABA. Finally, two Lactococcus (Lac.) lactis strains were selected for GABA production optimization via Response Surface Methodology (RSM) following Central Composite Design (CCD). Forty-one out of the 50 isolates showed GAD activity according to the colorimetric assay. Eight isolates displayed strong GAD activity, while nine showed no activity; low to moderate GAD activity was scored for all other isolates. GABA production was confirmed by TLC in all isolates with high GAD activity and in four selected among isoaltes with moderate activity. Among the Lactococcus strains tested, Lac. lactis 311 and Lac. lactis 491 were the strongest GABA producers with amounts of 3.3 and 1.26 mM, respectively. These two strains were subjected to GABA production optimization applying RSM and CCD on three key variables: Monosodium glutamate concentration (MSG) (between 25 and 150 mM), incubation temperature (between 25 and 37 °C), and pH (between 4.0 and 5.0). Optimal conditions for GABA production by Lac. lactis 311 and Lac. lactis 491 of temperature, pH and MSG concentration were, respectively, 35.4 and 30 °C, pH 4.5 and 4.6, and MSG concentration of 89 and 147.4 mM, respectively. Under the above conditions, the amount of GABA produced by Lac. lactis 311 and Lac. lactis 491 was 0.395 and 0.179 mg/mL, respectively. These strains and the optimal culture conditions determined in this study could be used for the biotechnological production of GABA or applied in food fermentations for the development of naturally GABA-enriched foods.

Production of gamma-aminobutyric acid by lactic acid bacteria of marine origin from Vietnam

Gamma-aminobutyric acid (GABA) is a non-proteinogenic amino acid, which functions as a neurotransmitter in the central nervous system. GABA has been shown to have several positive effects on human health, including reducing anxiety and promoting relaxation. In this study, various fermented fish products were screened for their ability to produce GABA. A total of 35 acid lactic producing strains were isolated from 8 samples of marine organism, 10 strains were found to have GABA-producing abilities. These strains were identified using 16S rDNA sequencing. The GABA concentrations produced by the 10 isolates ranged from 725 to 5590 mg/L. Lactobacillus brevis GB111 is the best isolated GABA producing strain, with a conversion rate up to 90.3%, which suggests that these strains may have potential applications in the food and pharmaceutical industries as a source of GABA.

GABA and fermented litchi juice enriched with GABA promote the beneficial effects in ameliorating obesity by regulating the gut microbiota in HFD-induced mice.

Gamma-aminobutyric acid (GABA) dietary intervention is considered to have therapeutic potential against obesity. Microbial enrichment is an effective strategy to naturally and safely enhance GABA production in food. As litchi is "the king of GABA" in fruits, the retention or enrichment of its content during processing has been a key issue in the litchi industry. This study aimed to investigate the potential of GABA and fermented litchi juice enriched with GABA (FLJ) to protect against obesity in a high-fat diet (HFD) mouse model. Supplementation of GABA and FLJ displayed an anti-obesogenic effect by attenuating body weight gain, fat accumulation, and oxidative damage, and improving the serum lipid profile and hepatic function. Sequencing (16S rRNA) of fecal samples indicated that GABA and FLJ intervention displayed different regulatory effects on HFD-induced gut microbiota dysbiosis at different taxonomic levels. The microbial diversity, the relative abundance of Firmicutes and Bacteroidetes as well as the F/B ratio of GABA and FLJ groups were reversed compared to those of the HFD-induced mice. Our finding broadens the potential mechanisms by which GABA regulates gut flora in the amelioration of obesity and provides guidance for developing FLJ as a functional food to prevent obesity.

Gamma aminobutyric acid production by commercially available probiotic strains.

Certain bacteria can produce gamma aminobutyric acid (GABA) from glutamate in the human intestinal tract, leading to the possibility of altering GABA levels through diet. To this end, we assessed the ability of seven commercially available probiotic supplements to produce GABA. Probiotic strains were compared for GABA production in pure culture. The bacteria were inoculated at a concentration of 107 CFU ml-1 in 10 ml MRS supplemented with monosodium glutamate (1%w/v), both with and without oligofructose-enriched inulin (OFI) (1%w/v). Two strains with the highest production of GABA were further assessed for 48 h in pH-controlled anaerobic batch cultures inoculated with faecal bacteria. Liquid chromatography-mass spectrometry (LC-MS) was used for quantification of GABA and microbiota composition was determined through 16S rRNA gene sequencing. Levilactobacillus brevis LB01 (CGMCC 16921) and Lactiplantibacillus plantarum 299v (DSM 9843) were the most efficient producers of GABA. High GABA levels (28.32 mmol l-1±0.29) were produced by the probiotic strain L. brevis LB01 at pH 5.4-5.6. This was significantly higher than the levels of GABA produced by L. plantarum (4.8 mmol l-1±6.8) and a negative control (2.9 mM±3.1). The addition of OFI did not further stimulate GABA production under the conditions tested. The ability of these strains to produce GABA in-vitro was further evaluated in a faecal microbiota environment. Once again, L.brevis LB01 produced the highest levels of GABA (40.24 mmol l-1±20.98). L. brevis LB01 was found to be the most efficient probiotic strain, of those tested, for GABA production.