GABA Production Research Articles

Lacticaseibacillus rhamnosus LRJ-1 alleviates constipation through promoting gut Bacteroides-derived γ-aminobutyric acid production

Multiple gastrointestinal disorders are associated with impaired gut microbiota. Probiotic Lacticaseibacillus rhamnosus can improve bowel disorder, however, the action mechanism is poorly understood. We integrated multi-omics data from the gut metagenome, metabolome, and colon transcriptome of constipated mice underlying L. rhamnosus LRJ-1 treatment to provide insights into host-microbial metabolic pathway. We found that oral administration of L. rhamnosus LRJ-1 alleviated constipation in mice accompanied by the increased abundances of fecal γ-aminobutyric acid (GABA) and intestinal commensal Bacteroides, and the activation of host GABAergic synapses. B. uniformis was the most enriched Bacteroides species in constipated mice treated with L. rhamnosus LRJ-1, and contributed to the increased abundance of GABA in the gut. Administration of either B. uniformis ATCC 8492 or GABA alleviated constipation and increased gastrointestinal motility in constipated mice. Knockout of the GABA biosynthetic gad gene in B. uniformis ATCC 8492 decreased GABA production and blocked its beneficial effects on constipation. These results confirm the therapeutic potential of L. rhamnosus LRJ-1 in alleviating constipation through promoting gut commensal Bacteroides-derived GABA production. Targeting the gut microbiome to regulate GABA production may open new insights for efficient constipation treatment.

γ-Aminobutyric Acid Alleviates Salinity-Induced Impairments in Rice Plants by Improving Photosynthesis and Upregulating Osmoprotectants and Antioxidants

Salt stress is a significant abiotic stress that hinders the growth of rice (Oryza sativa L.) and reduces their yield. Previous research has examined the synthesis of γ-aminobutyric acid (GABA) and its role in plant resistance under various abiotic stresses. However, the synthesis of GABA and its ability to mitigate damage caused by salt stress—particularly its effects on osmotic adjustment, antioxidant defense, photosynthesis, and overall plant growth throughout the entire rice lifecycle—remains unclear. Therefore, we conducted two experiments using salt-tolerant rice cultivar Lianjian 5 (J-5) and salt-susceptible cultivar Lianjing 7 (L-7). In Experiment I, RNA-seq (RNA sequencing) was used to analyze the differential expression of the transcriptome between CK and salinity treatments, revealing the key roles of GABA in salt tolerance. In Experiment II, different levels of exogenous GABA were applied to salt-stressed plants to investigate its physiological role in enhancing salt tolerance. Therefore, RNA-seq (RNA sequencing) was used to analyze the differential expression of the transcriptome between CK and salinity treatments, revealing the key roles of GABA in salt tolerance. Subsequently, different levels of exogenous GABA were applied to salt-stressed plants to investigate its physiological role in enhancing salt tolerance. We measured the activities of superoxide dismutase, peroxidase, and catalase, as well as photosynthetic characteristics such as photosynthesis, transpiration, chlorophyll content, stomatal density and size, and leaf anatomical features. The RNA-seq analysis revealed that GABA production is enhanced via the glutamate decarboxylase (GAD) gene (LOC4333932) in the salt-resistant rice cultivar. Exogenous GABA application improves salt-stress tolerance by increasing endogenous ABA and GABA contents, which enhance osmotic adjustment, boost antioxidant defenses, and regulate ion balance. These combined effects help maintain photosynthetic efficiency and support overall plant growth under salt-stressed environments. Additionally, the increased proportion of mesophyll cell periphery covered by chloroplasts (Sc/Sm) indicated enhanced mesophyll conductance. These helped maintain photosynthesis under saline conditions while reducing water consumption.

Advances in Plant GABA Research: Biological Functions, Synthesis Mechanisms and Regulatory Pathways.

The γ-aminobutyric acid (GABA) is a widely distributed neurotransmitter in living organisms, known for its inhibitory role in animals. GABA exerts calming effects on the mind, lowers blood pressure in animals, and enhances stress resistance during the growth and development of plants. Enhancing GABA content in plants has become a focal point of current research. In plants, GABA is synthesized through two metabolic pathways, the GABA shunt and the polyamine degradation pathway, with the GABA shunt being the primary route. Extensive studies have investigated the regulatory mechanisms governing GABA synthesis. At the genetic level, GABA production and degradation can be modulated by gene overexpression, signaling molecule-induced expression, transcription factor regulation, and RNA interference. Additionally, at the level of transporter proteins, increased activity of GABA transporters and proline transporters enhances the transport of glutamate and GABA. The activity of glutamate decarboxylase, a key enzyme in GABA synthesis, along with various external factors, also influences GABA synthesis. This paper summarizes the biological functions, metabolic pathways, and regulatory mechanisms of GABA, providing a theoretical foundation for further research on GABA in plants.

The Role of Lactic Acid Bacteria in Meat Products, Not Just as Starter Cultures.

Lactic acid bacteria (LABs) are microorganisms of significant scientific and industrial importance and have great potential for application in meat and meat products. This comprehensive review addresses the main characteristics of LABs, their nutritional, functional, and technological benefits, and especially their importance not only as starter cultures. LABs produce several metabolites during their fermentation process, which include bioactive compounds, such as peptides with antimicrobial, antidiabetic, antihypertensive, and immunomodulatory properties. These metabolites present several benefits as health promoters but are also important from a technological point of view. For example, bacteriocins, organic acids, and other compounds are of great importance, whether from a sensory or product quality or a safety point of view. With the production of GABA, exopolysaccharides, antioxidants, and vitamins are beneficial metabolites that influence safety, technological processes, and even health-promoting consumer benefits. Despite the benefits, this review also highlights that some LABs may present virulence properties, requiring critical evaluation for using specific strains in food formulations. Overall, this review hopes to contribute to the scientific literature by increasing knowledge of the various benefits of LABs in meat and meat products.

6674 Non-Progressive Diabetes Leading to Neurologic Diagnosis

Abstract Disclosure: F.L. Thelmo: None. M. Murugesh: None. B. Simon: None. Introduction: The autoantibody GAD (anti-glutamic acid decarboxylase) is highly associated with Type 1 diabetes (T1DM) and Latent Autoimmune Diabetes in Adulthood (LADA). If GAD is detected before the onset of overt diabetes, typically 80% of patients with abnormal glucose tolerance progress to insulin deficiency and the need for insulin treatment after 5 years.[1] Stiff Person Syndrome (SPS) is also associated with GAD antibodies, but in SPS, the GAD antibodies are believed to be different epitopes that target GABA production in neuromuscular pathways. We present a case of presumed LADA that did not progress for 30 years, with progressive neurologic symptoms leading to a diagnosis of SPS in later adulthood.Case: A 52-year-old female presented for evaluation of T1DM and worsening neuropathies. She had a long history of prediabetes, with mildly elevated glucose values noted on labs since her early twenties. There was no family history of T1DM or autoimmune conditions. Six years ago, she sought endocrine evaluation. HgbA1c values were 6.1 to 6.6%. Intermittent use of continuous glucose monitoring (CGM) revealed post-prandial hyperglycemia up to 180mg/dL, occasionally (but rarely) exceeding 200mg/dL. She recalls being told that she had positive antibodies (unclear which ones tested) and given a diagnosis of T1DM. She declined insulin and maintained glycemic control with carbohydrate restriction and exercise; there were no episodes of diabetic ketoacidosis. She then developed neurologic symptoms: fullness, tightness and bloating in the abdomen (diagnosed with gastroparesis on scanning) and after a COVID 19 booster in 2021, muscle spasms in the legs and back with worsening abdominal tightness. At the time of her current presentation, A1C was 6.4%, glycated albumin was 14.4% (prediabetes range 13.6 - 15.5%) and CGM time in range was 99%. A non-fasting C-peptide was 3.6 ng/mL (1.1- 4.4ng/mL) with glucose of 119 mg/dL. Repeat antibody testing revealed undetectable IA-2 and ZnT8 antibodies, but GAD was grossly elevated at 1,015.3 U/mL. Given the unusually high GAD titer, SPS was suspected, and this diagnosis was confirmed on referral to neurology. The patient was advised to liberalize diet and will be monitored with HgbA1c and serial C-peptide levels to assess progression in the future. Discussion: While high GAD antibody levels are associated with progression to insulin dependence in adults with LADA, in SPS the GAD titers tend to be even higher2. The presence of only one auto-antibody for T1DM (and not multiple), long-standing non-progressive hyperglycemia, and normal C-peptide pointed away from autoimmune diabetes being the etiology for mild glucose intolerance in this patient. If neurologic symptoms are present, high GAD should prompt the evaluation for other syndromes associated with GAD antibody epitopes such as SPS. Presentation: 6/2/2024

Enhanced γ-aminobutyric acid production by Co-culture fermentation with Enterococcus faecium AB157 and Saccharomyces cerevisiae SC125

γ-aminobutyric acid (GABA), a non-protein amino acid, is a major inhibitory neurotransmitter within the human nervous system. Research on enhancing GABA production through the co-culture of yeast and lactic acid bacteria is limited, and the intricacies of their interactions and the mechanisms behind GABA enhancement are not fully elucidated. In this study, five yeast strains from Sichuan Pao Cai were co-cultured with Enterococcus faecium AB157 to increase GABA content, and it was found that combining E. faecium AB157 with Saccharomyces cerevisiae SC125 at a 4:1 ratio, along with 12 g/L MSG, at 35 °C, optimized GABA production to reach levels of 6.57 g/L. Within the co-culture system, there was a notable increase in both glutamate decarboxylase activity (GAD) and medium pH, while the activity of Autoinducer-2 (AI-2) remained stable. Furthermore, the cell-free supernatants (CFS) from S. cerevisiae SC125 were able to enhance GABA production by E. faecium AB157, up to 4.61 g/L. RNA sequencing revealed that the GABA biosynthetic pathways and quorum sensing (QS) in co-fermentation on E. faecium AB157 were upregulated, and the ATP synthesis and arginine deiminase pathway were downregulated compare to the pure culture of E. faecium AB157.

Medium Formulation and Optimisation of Fermentation Condition Enhancing γ-aminobutyric Acid (GABA) Biosynthesis by Lactiplantibacillus plantarum B7

Extensive studies on γ-aminobutyric acid (GABA) over decades highlight its significant physiological and pharmacological effects on humans. GABA produced using microbe is favoured compared to enzymatic and chemical methods due to operational ease and reduced harmful pollutant formation. This study focused on increasing γ-aminobutyric acid (GABA) biosynthesis from Lactiplantibacillus plantarum B7, employing a multi-step optimisation strategy. An unoptimised cultivation approach yielded a maximum GABA of 11.68 ± 0.04 g/L and viable cell count of 10.47 ± 0.01 log CFU/mL at 48 h. A nutrient-rich medium was developed through single-parameter optimisation, comprising 1%, 2.5% and 0.0002% of glucose, yeast extract and each trace element (CaCO3, KI, and Tween 80) respectively. Temperature, pH, incubation period, initial concentration of monosodium glutamate (MSG) and pyridoxal-5’-phosphate (PLP) demonstrated significant contributions towards GABA production and cell growth as determined using a two-level factorial design. Steepest ascent identified optimal conditions (36°C, pH 5.5, 370 mM MSG, and 0.7 mM PLP), resulting in 30.50 g/L GABA and 11.51 log CFU/mL at 60 h. Further refinement via a central composite experiment yielded optimal conditions (temperature-35.6°C, pH-5.66, initial MSG concentration-335.61 mM, PLP concentration-0.723 mM) with improved GABA production (32.18 g/L) and cell growth (11.52 log CFU/mL) over 63.66 h. Therefore, this approach utilising lactic acid bacteria capable of GABA synthesis holds promise for mass-produced, enhanced-functional foods.

Production of γ-aminobutyric acid by immobilization of two Yarrowia lipolytica glutamate decarboxylases on electrospun nanofibrous membrane

This study harnesses glutamate decarboxylase (GAD) from Yarrowia lipolytica to improve the biosynthesis of γ-aminobutyric acid (GABA), focusing on boosting the enzyme's catalytic efficiency and stability by immobilizing it on nanofibrous membranes. Through recombinant DNA techniques, two GAD genes, YlGAD1 and YlGAD2, were cloned from Yarrowia lipolytica and then expressed in Escherichia coli. Compared to their soluble forms, the immobilized enzymes exhibited significant improvements in thermal and pH stability and increased resistance to chemical denaturants. The immobilization notably enhanced substrate affinity, as evidenced by reduced Km values and increased kcat values, indicating heightened catalytic efficiency. Additionally, the immobilized YlGAD1 and YlGAD2 enzymes showed substantial reusability, maintaining 50% and 40% of their activity, respectively, after six consecutive cycles. These results underscore the feasibility of employing immobilized YlGAD enzymes for cost-effective and environmentally sustainable GABA production. This investigation not only affirms the utility of YlGADs in GABA synthesis but also underscores the advantages of enzyme immobilization in industrial settings, paving the way for scalable biotechnological processes.

Unraveling the Potential of γ-Aminobutyric Acid: Insights into Its Biosynthesis and Biotechnological Applications.

γ-Aminobutyric acid (GABA) is a widely distributed non-protein amino acid that serves as a crucial inhibitory neurotransmitter in the brain, regulating various physiological functions. As a result of its potential benefits, GABA has gained substantial interest in the functional food and pharmaceutical industries. The enzyme responsible for GABA production is glutamic acid decarboxylase (GAD), which catalyzes the irreversible decarboxylation of glutamate. Understanding the crystal structure and catalytic mechanism of GAD is pivotal in advancing our knowledge of GABA production. This article provides an overview of GAD's sources, structure, and catalytic mechanism, and explores strategies for enhancing GABA production through fermentation optimization, metabolic engineering, and genetic engineering. Furthermore, the effects of GABA on the physiological functions of animal organisms are also discussed. To meet the increasing demand for GABA, various strategies have been investigated to enhance its production, including optimizing fermentation conditions to facilitate GAD activity. Additionally, metabolic engineering techniques have been employed to increase the availability of glutamate as a precursor for GABA biosynthesis. By fine-tuning fermentation conditions and utilizing metabolic and genetic engineering techniques, it is possible to achieve higher yields of GABA, thus opening up new avenues for its application in functional foods and pharmaceuticals. Continuous research in this field holds immense promise for harnessing the potential of GABA in addressing various health-related challenges.

Gaba-producing lactobacilli boost cognitive reactivity to negative mood without improving cognitive performance: A human Double-Blind Placebo-Controlled Cross-Over study

BackgroundPsychobiotic bacteria are probiotics able to influence stress-related behavior, sleep, and cognitive outcomes. Several in vitro and human studies were performed to assess their physiological potential, to find strains having psychotropic activity in humans, and to elucidate the metabolic pathways involved. In our previous in vitro study, we identified two strains Levilactobacillus brevis P30021 and Lactiplantibacillus plantarum P30025, able to produce GABA and acetylcholine, being promising candidates to provide an effect on mood and cognitive performance. AimTo investigate the effects of probiotics in the alleviation on the cognitive performance of moderately stressed healthy adults. Secondary outcomes were related to mood improvement, production of GABA, glutamate, acetylcholine, and choline and modification of the microbiota composition. MethodsA 12-week randomized, double-blind, placebo-controlled, cross-over study investigated the effects of a probiotic formulation (Levilactobacillus brevis P30021 and Lactiplantibacillus plantarum P30025) on psychological, memory, and cognition parameters in 44 (Probiotic = 44, Placebo = 43) adults with a mean age of 29 ± 5.7 years old by CogState Battery test. Subjects-inclusion criteria was a mild-moderate (18.7 ± 4.06) stress upon diagnosis using the DASS-42 questionnaire. ResultsProbiotic treatment had no effect on subjective stress measures. The probiotic formulation showed a significant beneficial effect on depressive symptoms by reducing cognitive reactivity to sad mood (p = 0.034). Rumination significantly improved after intake of the probiotic (p = 0.006), suggesting a potential benefit in reducing the negative cognitive effects associated with depression and improving overall mental health. When stratifying the treated subjects according to the response, we found an increase in the abundance of the probiotic genera in the gut microbiota of positive responders (p = 0.009 for Lactiplantibacillus and p = 0.004 for L.brevis). No relevant correlations were observed between the neurotransmitter concentration in the faecal sample, scores of LEIDS, DASS-42, and cognitive tests. ConclusionWe highlight the potential of this probiotic preparation to act as psycobiotics for the relief of negative mood feelings. The assessment of the psychotropic effects of dietary interventions in human participants has many challenges. Further interventional studies investigating the effect of these psychobiotic bacteria in populations with stressed-related disorders are required including longer period of intervention and larger sample size in order to verify the effects of the treatment on further stress-related indicators.

Enterococcus avium from a traditional Chinese liquor fermentation system with the potential for the de novo synthesis of GABA

γ-Aminobutyric acid (GABA) is a prevalent nonprotein amino acid with diverse physiological functions, attracting considerable interest in the food industry. However, current GABA-producing strains require glutamate as a substrate for synthesis. Probiotics capable of de novo GABA synthesis using sugars without glutamate are crucial for developing novel foods. This study employed a pH indicator method to selectively screen for GABA-producing bacteria. Nineteen strains with fermentation liquid pH greater than 5 were obtained, all demonstrated the ability to synthesize GABA from Daqu. Among these strains, Enterococcus (E.) avium GL1 stood out for its high GABA production capacity, reaching 9.8 g/L when utilizing glucose for de novo GABA synthesis without monosodium glutamate (MSG). E. avium GL1 exhibited robust viability in challenging environments, maintaining stability in simulated gastric and intestinal fluids. As a potentially probiotic strain, E. avium GL1 achieved remarkable GABA production of 206.84 g/L with a production efficiency of 2.87 g/L/h, facilitated by automatic pH control during fermentation through continuous addition of glucose and MSG addition. This exceptional result represents the highest GABA production reported for E. avium, highlighting its significant potential for the development of innovative functional foods.

SLC45A4 encodes a mitochondrial putrescine transporter that promotes GABA de novo synthesis.

Solute carriers (SLC) are membrane proteins that facilitate the transportation of ions and metabolites across either the plasma membrane or the membrane of intracellular organelles. With more than 450 human genes annotated as SLCs, many of them are still orphan transporters without known biochemical functions. We developed a metabolomic-transcriptomic association analysis, and we found that the expression of SLC45A4 has a strong positive correlation with the cellular level of γ-aminobutyric acid (GABA). Using mass spectrometry and the stable isotope tracing approach, we demonstrated that SLC45A4 promotes GABA de novo synthesis through the Arginine/Ornithine/Putrescine (AOP) pathway. SLC45A4 functions as a putrescine transporter localized to the mitochondrial membrane to facilitate GABA production. Taken together, our results revealed a new biochemical mechanism where SLC45A4 controls GABA production.

Probiogenomic analysis of Lactiplantibacillus plantarum SPS109: A potential GABA-producing and cholesterol-lowering probiotic strain

Lactiplantibacillus plantarum SPS109, an isolated strain of lactic acid bacteria (LAB) from fermented foods, showed remarkable potential as a probiotic with dual capabilities in γ-aminobutyric acid (GABA) production and cholesterol reduction. This study employs genomic and comparative analyses to search into the strain's genetic profile, safety features, and probiotic attributes. The safety assessment reveals the absence of virulence factors and antimicrobial resistance genes, while the genome uncovers bacteriocin-related elements, including sactipeptides and a cluster for putative plantaricins, strengthening its ability to combat diverse pathogens. Pangenome analysis revealed unique bacteriocin-related genes, specifically lcnD and bcrA, distinguishing SPS109 from four other L. plantarum strains producing GABA. In addition, genomic study emphasizes SPS109 strain distinctive features, two GABA-related genes responsible for GABA production and a bile tolerance gene (cbh) crucial for cholesterol reduction. Additionally, the analysis highlights several genes of potential probiotic properties, including stress tolerance, vitamin production, and antioxidant activity. In summary, L. plantarum SPS109 emerges as a promising probiotic candidate with versatile applications in the food and beverage industries, supported by its unique genomic features and safety profile.

Comprehensive characterization of γ-aminobutyric acid (GABA) production by Levilactobacillus brevis CRL 2013: insights from physiology, genomics, and proteomics.

Levilactobacillus brevis CRL 2013, a plant-derived lactic acid bacterium (LAB) with immunomodulatory properties, has emerged as an efficient producer of γ-aminobutyric acid (GABA). Notably, not all LAB possess the ability to produce GABA, highlighting the importance of specific genetic and environmental conditions for GABA synthesis. This study aimed to elucidate the intriguing GABA-producing machinery of L. brevis CRL 2013 and support its potential for safe application through comprehensive genome analysis. A comprehensive genome analysis of L. brevis CRL 2013 was performed to identify the presence of antibiotic resistance genes, virulence markers, and genes associated with the glutamate decarboxylase system, which is essential for GABA biosynthesis. Then, an optimized chemically defined culture medium (CDM) was supplemented with monosodium glutamate (MSG) and yeast extract (YE) to analyze their influence on GABA production. Proteomic and transcriptional analyses were conducted to assess changes in protein and gene expression related to GABA production. The absence of antibiotic resistance genes and virulence markers in the genome of L. brevis CRL 2013 supports its safety for potential probiotic applications. Genes encoding the glutamate decarboxylase system, including two gad genes (gadA and gadB) and the glutamate antiporter gene (gadC), were identified. The gadB gene is located adjacent to gadC, while gadA resides separately on the chromosome. The transcriptional regulator gadR was found upstream of gadC, with transcriptional analyses demonstrating cotranscription of gadR with gadC. Although MSG supplementation alone did not activate GABA synthesis, the addition of YE significantly enhanced GABA production in the optimized CDM containing glutamate. Proteomic analysis revealed minimal differences between MSG-supplemented and non-supplemented CDM cultures, whereas YE supplementation resulted in significant proteomic changes, including upregulation of GadB. Transcriptional analysis confirmed increased expression of gadB and gadR upon YE supplementation, supporting its role in activating GABA production. These findings provide valuable insights into the influence of nutrient composition on GABA production. Furthermore, they unveil the potential of L. brevis CRL 2013 as a safe, nonpathogenic strain with valuable biotechnological traits which can be further leveraged for its probiotic potential in the food industry.

GABA production induced by imipridones is a targetable and imageable metabolic alteration in diffuse midline gliomas.

Imipridones induce GABA accumulation in diffuse midline gliomas, an effect that can be leveraged for therapy and non-invasive imaging.

Enrichment of corn and alfalfa silage with γ-aminobutyric acid through inoculation with a screened high producing Lentilactobacillus buchneri strain

This study aimed to enrich corn and alfalfa silages with γ-aminobutyric acid (GABA) by utilizing high GABA-producing Lentilactobacillus buchneri. Eleven strains were screened and L. Buchneri YM9 was distinguished for its superiority in GABA production, and it was subsequently applied as an inoculant on whole-crop corn and alfalfa silage. The silage treatments were control (without inoculant), AH35 (non-GABA producing strain), YM9 (high-GABA producing strain), and 40788 (commercial GABA producing strain). The results revealed that in corn silage, pH significantly declined at the initial ensiling stage (3–7 days), with the control having the lowest pH after 90 days. The control also exhibited the highest lactic acid, while L. buchneri treatments had elevated acetic acid. Similar trends were observed in alfalfa silage, with 30 % dry matter (DM) showing lower pH and higher organic acids. YM9-inoculated corn silage had higher DM loss, reduced water-soluble carbohydrates (WSC), but increased crude protein (CP) content. YM9 and 40788 treatments in whole-crop corn silage had lower glutamate (Glu) content post-ensiling, signifying effective GABA production. YM9 treatment maintained stable and higher glutamate decarboxylase (GAD) activity, resulting in the highest GABA accumulation in corn silage (1.97 g/kg DM). Likewise, YM9 and 40788 demonstrated significantly higher GABA content in 30 % (7.6 and 6.51 g/kg DM) and 40 % (5.23 and 5.32 g/kg DM) DM alfalfa silage. Beyond enhancing fermentation and nutrient preservation, YM9 strain shows promise in enriching whole-crop corn and alfalfa with ample GABA concentration, potentially exerting anticipated biological functions when consumed by animals.

Optimization of fermentation conditions for the production of γ-aminobutyric acid by Lactobacillus hilgardii GZ2 from traditional Chinese fermented beverage system.

γ-Aminobutyric acid (GABA) is a crucial neurotransmitter with wide application prospects. In this study, we focused on a GABA-producing strain from a traditional Chinese fermented beverage system. Among the six isolates, Lactobacillus hilgardii GZ2 exhibited the greatest ability to produce GABA in the traditional Chinese fermented beverage system. To increase GABA production, we optimized carbon sources, nitrogen sources, temperature, pH, and monosodium glutamate and glucose concentrations and conducted fed-batch fermentation. The best carbon and nitrogen sources for GABA production and cell growth were glucose, yeast extract and tryptone. Gradual increases in GABA were observed as the glucose and monosodium glutamate concentrations increased from 10g/L to 50g/L. During fed-batch fermentation, lactic acid was used to maintain the pH at 5.56, and after feeding with 0.03g/mL glucose and 0.4g/mL sodium glutamate for 72h, the GABA yield reached 239g/L. This novel high-GABA-producing strain holds great potential for the industrial production of GABA, as well as the development of health-promoting functional foods and medical fields.

Stepwise Flux Optimization for Enhanced GABA Production from Acetate in Escherichia coli.

Strategic allocation of metabolic flux is essential for achieving a higher production performance in genetically engineered organisms. Flux optimization between cell growth and chemical production has led to the establishment of cost-effective chemical production methods in microbial cell factories. This effect is amplified when utilizing a low-cost carbon source. γ-Aminobutyric acid (GABA), crucial in pharmaceuticals and biodegradable polymers, can be efficiently produced from acetate, a cost-effective substrate. However, a balanced distribution of acetate-derived flux is essential for optimizing the production without hindering growth. In this study, we demonstrated GABA production from acetate using Escherichia coli by focusing on optimizing the metabolic flux at isocitrate and α-ketoglutarate nodes. Through a series of flux optimizations, the final strain produced 2.54 g/L GABA from 5.91 g/L acetate in 24 h (0.43 g/g yield). These findings suggest that delicate flux balancing with the application of a cheap substrate can contribute to cost-effective production of GABA.

Effects of different soaking and germinating conditions on γ-aminobutyric acid, antioxidant activity, and chemical composition of djulis (Chenopodium formosanum)

Djulis (Chenopodium formosanum), a native plant of Taiwan, is esteemed for its rich nutritional profile, encompassing high levels of dietary fiber, proteins, essential amino acids, and microelements. This study delved into the influence of soaking and germinating conditions on the synthesis of γ-aminobutyric acid (GABA), total phenolic content (TPC), antioxidant activity, and enzymatic activity in djulis. Enrichment culture tests were conducted to ascertain optimal soaking conditions. Results revealed that soaking djulis seeds for 4 h at 25 °C before germination notably augmented GABA production. Furthermore, djulis seeds subjected to soaking and germination at 30 °C for 48 h exhibited heightened GABA and anthocyanin contents. Conversely, germination at 25 °C for 48 h demonstrated superior TPC and 2,2-diphenylpicrylhydrazyl (DPPH) free radical scavenging activity. Optimal concentrations of glutamic acid, monosodium glutamate, pyridoxal-5′-phosphate (vitamin B6), Ca2+, and pH were found to enhance glutamine acid decarboxylase activity, consequently elevating GABA content. In summary, fine-tuning soaking and germinating conditions presents a promising avenue for augmenting GABA production in djulis, thereby bolstering its nutritional and functional utility. Future investigations aimed at elucidating the molecular mechanisms underlying enzymatic activity modulation during soaking and germination could yield valuable insights into optimizing GABA production.

Safety and Beneficial Properties of Bacteriocinogenic Lactococcus lactis and Pediococcus pentosaceus Strains, and Their Effect Versus Oral Cavity Related and Antibiotic-Resistant Pathogens.

Pediococcus pentosaceus 732, Lactococcus lactis subsp. lactis 431, and Lactococcus lactis 808, bacteriocinogenic strains previously isolated from kimchi and banana, were investigated for their safety, beneficial properties and in vitro inhibition of pathogens such as Listeria monocytogenes ATCC 15313 and Staphylococcus simulans KACC 13241 and Staphylococcus auricularis KACC 13252. The results of performed physiological, biochemical, and biomolecular tests suggest that these strains can be deemed safe, as no virulence genes were detected in their DNA. Notably, only the gad gene associated with GABA production was identified in the DNA isolated of Lc. lactis 808 and Lc. lactis subsp. lactis 431 strains. All tested LAB strains exhibited γ-hemolysins and were non-producers of gelatinase and biogenic amines, which suggested their safety potential. Additionally, they were relatively susceptible to antibiotics except for streptomycin, tobramycin, and vancomycin for Pd. pentosaceus 732. The growth of Pd. pentosaceus 732, Lc. lactis subsp. lactis 431, and Lc. lactis 808 and their survival were minimally affected by up to 3% ox bile and low pH (except pH 2.0 and 4.0). Moreover, these LAB strains were not inhibited by various commercial extracts as well as most of the tested medications tested in the study. They did not produce proteolytic enzymes but exhibited production of D/L-lactic acid and β-galactosidase. They were also hydrophilic. Furthermore, their survival in artificial saliva, gastric simulation, and enteric passage was measured followed by a challenge test to assess their ability to inhibit the selected oral pathogens in an oral saliva model conditions.