Gamma-aminobutyric acid as a bioactive compound in foods: a review

Effect of Additives on the Morphology of γ-Aminobutyric Acid Crystals

The effect of surfactant, polymer, and tailor-made additives on the crystallization of γ-aminobutyric acid (GABA) was studied in this work. Cooling crystallization of GABA in water yielded plate-like crystals. In the presence of sodium stearate, polyhedral block-like crystals of GABA were obtained. Hydroxyethyl cellulose (HEC) led to rod-like crystals, in which the morphology was associated with additive concentrations. Six kinds of amino acids were used as tailor-made additives, and they exhibit different influences on crystal shape and size. The induction time of GABA was determined in the absence and presence of additives. The results showed that sodium stearate promoted nucleation, while HEC, l-Lysine, l-histidine, and l-tyrosine inhibited nucleation. Crystal face indexing, Hirshfeld surface analysis, and molecular dynamics (MD) simulation in aqueous solution-crystal systems were carried out to investigate the affecting factors of different crystal faces. The polymer additive was selected as an example during MD simulation to calculate intermolecular interactions between the crystal face and solvent or additive. The effect of the additive on the mobility of the solute in solution was also evaluated by mean-square displacement. The additive offers an effective approach for changing crystal morphology and particle size and adapting it to different production requirements.

Impact of Germination on the Edible Quality and Nutritional Properties of Brown Rice Noodles

Brown rice noodles are increasingly favored by consumers for their health benefits; however, their development is hindered by their poor edible qualities. The effect of germination on the cooking, textural, organoleptic and nutritional qualities of brown rice pasta was investigated. In comparison to ungerminated brown rice noodles, germination resulted in a shorter cooking time, reduced cooking losses, and decreased hardness and adhesion of noodles as well as reduced bitter taste. These changes can be attributed to germination altering the basic composition of brown rice. Meanwhile, the contents of γ-aminobutyric acid, free phenolic acid, and bound phenolic acid increased by 53.43%, 21.71%, and 7.14%, respectively, while the content of resistant starch de-creased by 21.55%. Sprouting is a promising strategy for improving the edible quality and nutritional properties of brown rice noodles.

Production of γ-aminobutyric acid-enriched sourdough bread using an isolated Pediococcus pentosaceus strain JC30

A γ-aminobutyric acid (GABA)-producing strain JC30 was isolated from traditional kimchi, which was identified as Pediococcus pentosaceus by 16S rDNA sequencing. P. pentosaceus JC30 was highly tolerant to acid, bile salt, and high temperatures. The survival rate of JC30 in MRS medium (pH 2.5) for 3 h was 60.96 %. Furthermore, the survival rate of JC30 in MRS medium with 3 mg/mL bile salt for 24 h was 86.62 %. The survival rate of JC30 in MRS medium at 56 °C and 58 °C for 10 min was 97.17 % and 78.20 %, respectively. When 2 % v/v JC30 (8.0 log10 CFU/mL) was added to prepare sourdough and the sourdough was then used to make bread, the bread had a higher specific volume (5.13 ± 0.12 mL/g) and GABA content (3.32 ± 0.04 mg/g DW) than the control.

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.

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.

Effect of different stress conditions on the formation of amino acid derivatives by Brewer's and Baker's yeast during fermentation

The effects of environmental stresses on the formation of amino acid derivatives by Saccharomyces cerevisiae NCYC 88 and Saccharomyces cerevisiae NCYC 79 were investigated. Fermentation was performed in model systems under different temperature, pH, alcohol, phenolic, and osmotic stress conditions, as well as in beer and dough. According to stress response molecules, yeasts were more affected by osmotic, temperature, and alcohol stresses. Both yeast strains increased the formation of kynurenic acid, tryptophan ethyl ester, tryptophol, and gamma-aminobutyric acid under osmotic stress conditions in model systems. Indole-3-acetic acid was found to be higher in the ferulic acid stress dough (262 µg/kg dry weight, d.w.) compared to the control dough (132 µg/kg d.w.) at the end of the fermentation. The results may enable the development of new strategies for designing novel foods with a desired composition of bioactive amino acid derivatives.

GABA synthesizing lactic acid bacteria and genomic analysis of Levilactobacillus brevis LAB6

This study was conducted to investigate the γ-aminobutyric acid (GABA) production ability of 20 Lactobacillus and 25 Bifidobacterium strains which were previously isolated in our laboratory. Effect of initial pH, incubation time, monosodium glutamate (MSG), and pyridoxal-5'-phosphate (PLP) concentration for highest GABA production by two potent bacterial strains, Levilactobacillus brevis LAB6 and Limosilactobacillus fermentum LAB19 were optimized in the MRS media. A threefold increase in GABA production at an initial pH 4.0, incubation time of 120 h in medium supplemented with 3% MSG and 400 μM of PLP for LAB6 and 300 μM for LAB19 lead to the production of 19.67 ± 0.28 and 20.77 ± 0.14 g/L of GABA, respectively. Coculturing both strains under optimized conditions led to a GABA yield of 20.02 ± 0.17 g/L. Owing to potent anti-inflammatory activity in-vitro, as reported previously, and highest GABA production ability of LAB6 (MTCC 25662), its whole-genome sequencing and bioinformatics analysis was carried out for mining genes related to GABA metabolism. LAB6 harbored a complete glutamate decarboxylase (GAD) gene system comprising gadA, gadB, and gadC as well as genes responsible for the beneficial probiotic traits, such as for acid and bile tolerance and host adhesion. Comparative genomic analysis of LAB6 with 28 completely sequenced Levilactobacillus brevis strains revealed the presence of 95 strain-specific genes-families that was significantly higher than most other L. brevis strains.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03918-7.

Lactobacillus brevis-Fermented Gamma-Aminobutyric Acid Ameliorates Depression- and Anxiety-Like Behaviors by Activating the Brain-Derived Neurotrophic Factor-Tropomyosin Receptor Kinase B Signaling Pathway in BALB/C Mice

This study investigated the effects of Lactobacillus brevis-fermented gamma-aminobutyric acid (LB-GABA) on depressive and anxiety-like behaviors with the underlying molecular mechanism in a chronic stress model of BALB/c mice. LB-GABA attenuates both neuronal cell death and the increase of monoamine oxidase activity induced by hydrogen peroxide. Behavioral tests revealed that GABA significantly increased sucrose preference and reduced immobility time in both tail suspension and forced swimming tests. LB-GABA increased exploration of the open arms in the elevated plus maze and restored activity in the open field. Moreover, LB-GABA lowered stress hormone and inflammatory mediator levels. Mechanistically, LB-GABA increased protein levels of BDNF and TrkB, activating downstream targets (AKT, ERK, and CREB), crucial for neuronal survival and plasticity. Furthermore, LB-GABA protected hippocampal neurons from stress-induced cell death and increased serotonin and dopamine levels. Overall, LB-GABA has the potential to alleviate stress-induced depression and anxiety-like symptoms and neuroinflammation by activating the BDNF-TrkB signaling pathway.

Exopolysaccharides of lactic acid bacteria: Structure, biological activity, structure-activity relationship, and application in the food industry: A review

Over the past few decades, researchers have discovered that probiotics play an important role in our daily lives. With the further deepening of research, more and more evidence show that bacterial metabolites have an important role in food and human health, which opens up a new direction for the research of lactic acid bacteria (LAB) in the food and pharmaceutical industry. Many LAB have been widely studied because of the ability of exopolysaccharides (EPS). Lactic acid bacteria exopolysaccharides (LAB EPS) not only have great potential in the treatment of human diseases but also can become natural ingredients in the food industry to provide special qualitative structure and flavor. This paper has organized and summarized the biosynthesis, strain selection, production process parameters, structure, and biological activity of LAB EPS, filling in the monotony and incompleteness of previous articles' descriptions of LAB EPS. Therefore, this paper focuses on the general biosynthetic pathway, structural characterization, structure-activity relationship, biological activity of LAB EPS, and their application in the food industry, which will help to deepen people's understanding of LAB EPS and develop new active drugs from LAB EPS. Although the research results are relatively affluent, the low yield, complex structure, and few clinical trials of EPS are still the reasons that hinder its development. Therefore, future knowledge expansion should focus on the regulation of structure, physicochemical properties, function, higher production of EPS, and clinical trial applications, which can further increase the commercial significance and value of EPS. Furthermore, better understanding the structure-function relationship of EPS in food remains a challenge to date.

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.

Biosynthesis of Gamma-Aminobutyric Acid (GABA) by Lactiplantibacillus plantarum in Fermented Food Production

In recent decades, given the important role of gamma-aminobutyric acid (GABA) in human health, scientists have paid great attention to the enrichment of this chemical compound in food using various methods, including microbial fermentation. Moreover, GABA or GABA-rich products have been successfully commercialized as food additives or functional dietary supplements. Several microorganisms can produce GABA, including bacteria, fungi, and yeasts. Among GABA-producing microorganisms, lactic acid bacteria (LAB) are commonly used in the production of many fermented foods. Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) is a LAB species that has a long history of natural occurrence and safe use in a wide variety of fermented foods and beverages. Within this species, some strains possess not only good pro-technological properties but also the ability to produce various bioactive compounds, including GABA. The present review aims, after a preliminary excursus on the function and biosynthesis of GABA, to provide an overview of the current uses of microorganisms and, in particular, of L. plantarum in the production of GABA, with a detailed focus on fermented foods. The results of the studies reported in this review highlight that the selection of new probiotic strains of L. plantarum with the ability to synthesize GABA may offer concrete opportunities for the design of new functional foods.

Exploring the Therapeutic Potential of Gamma-Aminobutyric Acid in Stress and Depressive Disorders through the Gut-Brain Axis

Research conducted on individuals with depression reveals that major depressive disorders (MDDs) coincide with diminished levels of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) in the brain, as well as modifications in the subunit composition of the primary receptors (GABAA receptors) responsible for mediating GABAergic inhibition. Furthermore, there is substantial evidence supporting the significant role of GABA in regulating stress within the brain, which is a pivotal vulnerability factor in mood disorders. GABA is readily available and approved as a food supplement in many countries. Although there is substantial evidence indicating that orally ingested GABA may affect GABA receptors in peripheral tissues, there is comparatively less evidence supporting its direct action within the brain. Emerging evidence highlights that oral GABA intake may exert beneficial effects on the brain and psyche through the gut-brain axis. While GABA enjoys wide consumer acceptance in Eastern Asian markets, with many consumers reporting favorable effects on stress regulation, mood, and sleep, rigorous independent research is still largely lacking. Basic research, coupled with initial clinical findings, makes GABA an intriguing neuro-nutritional compound deserving of clinical studies in individuals with depression and other psychological problems.

Bioactive Ingredients from Dairy-Based Lactic Acid Bacterial Fermentations for Functional Food Production and Their Health Effects

Lactic acid bacteria are traditionally applied in a variety of fermented food products, and they have the ability to produce a wide range of bioactive ingredients during fermentation, including vitamins, bacteriocins, bioactive peptides, and bioactive compounds. The bioactivity and health benefits associated with these ingredients have garnered interest in applications in the functional dairy market and have relevance both as components produced in situ and as functional additives. This review provides a brief description of the regulations regarding the functional food market in the European Union, as well as an overview of some of the functional dairy products currently available in the Irish and European markets. A better understanding of the production of these ingredients excreted by lactic acid bacteria can further drive the development and innovation of the continuously growing functional food market.

Health-promoting germinated rice and value-added foods: a comprehensive and systematic review of germination effects on brown rice

Over the last 30 years, thousands of articles have appeared examining the effects of soaking and germinating brown rice (BR). Variable germination conditions and methods have been employed to measure different health-beneficial parameters in a diverse germplasm of BR. Research results may therefore appear inconsistent with occasional anomalies, and it may be difficult to reach consensus concerning expected trends. Herein, we amassed a comprehensive review on germinated brown rice (GBR), attempting to codify 133 peer-reviewed articles regarding the effects on 164 chemical parameters related to health and nutrition in BR and in value-added food products. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-2020) approach was used to direct the flow of the literature search. A pair-wise comparison t-test was performed to deliver an overall approach indicating when a given compound has been found to significantly increase or decrease through germination, which was grouped into GABA and polyamines, γ-Oryzanol and phytosterols, phenolic compounds, vitamins, proteins and amino acids, starchy carbohydrates, free sugars, lipids, minerals and phytic acid. This resource will stimulate interest in germinating rice and optimistically help increase both production and consumption of highly nutritious, health-beneficial rice with pigmented bran.

Formation of Histamine, phenylethylamine and γ-Aminobutyric acid during sprouting and fermenting of selected wholegrains

Sprouting and fermentation are known to cause hydrolysis of proteins into amino acids in grains, which in turn can be converted into some neuroactive compounds by some specific enzymes.One of these compounds is γ-aminobutyric acid, which is directly related to stress management. This study invesitgatesthe effects of sprouting and fermentation processes performed under different conditions on the formation of γ-aminobutyric acid.. Concomitant phenylethylamine and histamine formations were also investigated from the food safety point of view. The combined application of sprouting and fermentation increased the concentrations of histamine and phenylethylamine to a maximum of 44 ± 5 ​​ and 3.9 ± 0.002 mg/kg, respectively. Nevertheless, these values ​​did not reach the level that would cause undesirable effects. γ-Aminobutyric acid concentrations were found to reach levels comparable to γ-Aminobutyric acid -rich foods (maximum 674 ± 31 mg/kg) both with separate and combined application of sprouting and fermentation.

Ascertaining the Influence of Lacto-Fermentation on Changes in Bovine Colostrum Amino and Fatty Acid Profiles

The aim of this study was to collect samples of bovine colostrum (BCOL) from different sources (agricultural companies A, B, C, D and E) in Lithuania and to ascertain the influence of lacto-fermentation with Lactiplantibacillus plantarum strain 135 and Lacticaseibacillus paracasei strain 244 on the changes in bovine colostrum amino (AA), biogenic amine (BA), and fatty acid (FA) profiles. It was established that the source of the bovine colostrum, the used LAB, and their interaction had significant effects (p < 0.05) on AA contents; lactic acid bacteria (LAB) used for fermentation was a significant factor for aspartic acid, threonine, glycine, alanine, methionine, phenylalanine, lysine, histidine, and tyrosine; and these factor's interaction is significant on most of the detected AA concentrations. Total BA content showed significant correlations with glutamic acid, serine, aspartic acid, valine, methionine, phenylalanine, histidine, and gamma amino-butyric acid content in bovine colostrum. Despite the differences in individual FA contents in bovine colostrum, significant differences were not found in total saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids. Finally, the utilization of bovine colostrum proved to be challenging because of the variability on its composition. These results suggest that processing bovine colostrum into value-added formulations for human consumption requires the adjustment of its composition since the primary production stage. Consequently, animal rearing should be considered in the employed bovine colostrum processing technologies.

Association of plant-based diet index with sleep quality in middle-aged and older adults: The Healthy Dance Study

OBJECTIVES

To investigate the association between plant-based diet indices and sleep quality in Chinese middle-aged and older adults.

METHODS

The study included 2424 participants aged 45 years and older. Dietary data were collected using a semi-quantitative food frequency questionnaire, and sleep quality was assessed by the Pittsburgh Sleep Quality Index scale. Plant-based diet was categorized based on 3 indices (score range, 17-85) covering 17 food groups: the overall plant-based diet index, healthful plant-based diet index, and unhealthful plant-based diet index. The associations between these plant-based diet indices and sleep quality were examined using logistic and linear regression analyses.

RESULTS

After controlling for sociodemographic, lifestyle, and multiple disease-related factors, participants in the highest quartile of the healthful plant-based diet index had 0.55 higher odds of better sleep quality (95% CI: 0.42, 0.72; Ptrend< .001). In contrast, participants in the highest quartile of the unhealthful plant-based diet index had 2.03 higher odds of poor sleep quality (95% CI: 1.51, 2.72; Ptrend< .001). In addition, plant-based diet index and healthful plant-based diet index were inversely associated with Pittsburgh Sleep Quality Index scores, while unhealthful plant-based diet index and Pittsburgh Sleep Quality Index scores were positively associated.

CONCLUSIONS

We found unhealthy plant-based diets are significantly associated with poor sleep quality. Adherence to overall plant-based diets, especially healthy plant-based diets, was positively associated with optimal sleep quality.

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.

Chemical Composition, Fatty Acid Profile, and Optimization of the Sacha Inchi (Plukenetia volubilis L.) Seed-Roasting Process Using Response Surface Methodology: Assessment of Oxidative Stability and Antioxidant Activity

This study aimed to optimize the roasting conditions for sacha inchi (Plukenetia volubilis L.) seeds using the central composite design (CCD) of the response surface methodology (RSM). The antioxidant activity and oxidation indicators (peroxide and TBA values) were assessed, along with the impact of roasting on the fatty acid profile and chemical characterization of the seeds using gas chromatography. The results demonstrated that roasting partially increased the indicators of lipid oxidation in the oil extracted from roasted seeds, as well as the antioxidant activity of the seeds. The optimal roasting conditions were determined using CCD and RSM, resulting in an optimized temperature of 134.28 °C and 18.84 min. The fatty acid contents were not significantly affected by the roasting intensity, whereas a higher presence of amino acids was found in the seeds roasted at 140 °C for 15 min. In conclusion, it is suggested that the optimal roasting conditions for enhancing amino acid presence, improving antioxidant activity, and maintaining oxidative stability in sacha inchi seeds fall within the temperature range of 134-140 °C and a roasting duration of 15-20 min.

Natural diversity of lactococci in γ-aminobutyric acid (GABA) production and genetic and phenotypic determinants

BACKGROUND

γ-aminobutyric acid (GABA) is a bioactive compound produced by lactic acid bacteria (LAB). The diversity of GABA production in the Lactococcus genus is poorly understood. Genotypic and phenotypic approaches were therefore combined in this study to shed light on this diversity. A comparative genomic study was performed on the GAD-system genes (gadR, gadC and gadB) involved in GABA production in 36 lactococci including L. lactis and L. cremoris species. In addition, 132 Lactococcus strains were screened for GABA production in culture medium supplemented with 34 mM L-glutamic acid with or without NaCl (0.3 M).

RESULTS

Comparative analysis of the nucleotide sequence alignments revealed the same genetic organization of the GAD system in all strains except one, which has an insertion sequence element (IS981) into the PgadCB promoter. This analysis also highlighted several deletions including a 3-bp deletion specific to the cremoris species located in the PgadR promoter, and a second 39-bp deletion specific to L. cremoris strains with a cremoris phenotype. Phenotypic analysis revealed that GABA production varied widely, but it was higher in L. lactis species than in L. cremoris, with an exceptional GABA production of up to 14 and 24 mM in two L. lactis strains. Moreover, adding chloride increased GABA production in some L. cremoris and L. lactis strains by a factor of up to 16 and GAD activity correlated well with GABA production.

CONCLUSIONS

This genomic analysis unambiguously characterized the cremoris phenotype of L. cremoris species and modified GadB and GadR proteins explain why the corresponding strains do not produce GABA. Finally, we found that glutamate decarboxylase activity revealing GadB protein amount, varied widely between the strains and correlated well with GABA production both with and without chloride. As this protein level is associated to gene expression, the regulation of GAD gene expression was identified as a major contributor to this diversity.

Expression and Transformation Characteristics of a Novel Glutamic Acid Decarboxylase LcGAD10s and Its Application on Sufu Processing

Gamma-aminobutyric acid (GABA) is an important non-proteinogenic amino acid and a potent bioactive compound with many anti-hypertensive and anti-depressant activities. The bioconversion of GABA by glutamic acid decarboxylase (GAD) has been eagerly studied. Herein, novel pyridoxal-5-phosphate monohydrates (PLP)-dependent GAD, which is not quite similar to reporting, was cloned from Latilactobacillus curvatus and efficiently expressed in E. coli. The conveniently purified GAD (designated LcGAD10s) appeared as a single protein on SDS-PAGE with a molecular mass of 52.0 kDa. LcGAD10s exhibited a specific activity of 303.7 U/mg after purification by Ni-IDA affinity chromatography, with optimal activity at 55 °C and pH 5. LcGAD10s displayed excellent temperature (50 °C) and pH (4-8) stability which relative activity above 80% and 70%, respectively. The enzymatic activity was, respectively, increased and depressed by 130%, and 24% in the presence of Mn+ and Cu2+. Enzyme activity over 90% can be achieved by adding at least 25 mM of PLP. LcGAD10s was able to efficiently transform 15 g/L GABA with a single-factor optimized reaction of pH (5), temperature (50 °C), time (2 h), LcGAD10s dosage (0.4 U) and monosodium glutamate level (5 g/L). Additionally, LcGAD10s can be applied to a tofu fermentation system to achieve GABA conversion and achieved 14.9 mg/g of GABA conversion when added at 2 U/mL, which is higher than most of the commercial sufu and previous application reports, increasing its functional substances.

Integrating animal experiments, mass spectrometry and network-based approach to reveal the sleep-improving effects of Ziziphi Spinosae Semen and γ-aminobutyric acid mixture

BACKGROUND

Ziziphi Spinosae Semen (ZSS) is a plant widely used as medicine and food in Asian countries due to its numerous health benefits. γ-aminobutyric acid (GABA), a non-proteinaceous amino acid, is one of the major inhibitory neurotransmitters with a relaxant function. In this study, a system pharmacology approach was employed to assess the effects of a mixture composed of ZSS and GABA (ZSSG) on sleep improvement.

METHODS

Mice were divided into five groups (n = 10) and received either no treatment, sodium pentobarbital, or sodium barbital with diazepam or ZSSG. The effects of ZSSG on sleep quality were evaluated in mice, and differential metabolites associated with sleep were identified among the control, ZSS, GABA, and ZSSG groups. Additionally, network-based ingredient-insomnia proximity analysis was applied to explore the major ingredients.

RESULTS

ZSSG significantly improved sleep quality by decreasing sleep latency and prolonging sleep duration in sodium pentobarbital-induced sleeping mouse model (P < 0.05). ZSSG significantly enhanced the brain content of GABA in mice. Furthermore, ZSSG also significantly decreased sleep latency-induced by sodium barbital in mice (P < 0.05). Metabolic analysis revealed significant differences in 10 metabolites between ZSSG group and the groups administering ZSS or GABA. Lastly, using the network-based ingredient screening model, we discovered potential four active ingredients and three pairwise ingredient combinations with synergistic effect on insomnia from ZSSG among 85 ingredients identified by UPLC-Q/TOF-MS. Also, we have constructed an online computation platform.

CONCLUSION

Our data demonstrated that ZSSG improved the sleeping quality of mice and helped to balance metabolic disorders-associated with sleep disorders. Moreover, based on the network-based prediction method, the four potential active ingredients in ZSSG could serve as quality markers-associated with insomnia. The network-based framework may open up a new avenue for the discovery of active ingredients of herbal medicine for treating complex chronic diseases or symptoms, such as insomnia.

Gamma-Aminobutyric Acid (GABA) Biosynthesis from Lactobacillus plantarum subsp. plantarum IBRC10817 Optimized and Modeled in Response to Heat and Ultrasonic Shock

Gamma-aminobutyric acid is one of the major inhibitory neurotransmitters in the nervous system. Although gamma-aminobutyric acid is commonly synthesized by chemical methods, its microbial biosynthesis is regarded as one of the best production methods among the conventional techniques. This study aimed to optimize and model the production of gamma-aminobutyric acid from Lactobacillus plantarum subsp. plantarum IBRC (10,817) under the influence of heat and ultrasonic shock using the response surface methodology. Heat and ultrasonic shock were applied in the lag phase of bacterial growth. Heat shock variables included heat treatment, monosodium glutamate concentration, and incubation time. Also, ultrasonic shock variables were ultrasonic intensity, ultrasonic time, incubation time, and monosodium glutamate concentration. By applying the 30.9 h of incubation, 3.082 g/L of monosodium glutamate, and thermal shock of 49.958 °C for 30 min, the production of 295.04 mg/L of gamma amino butyric acid was predicted. As for ultrasonic shock, using 3.28 (g/L) monosodium glutamate, 70 h of bacterial incubation, 7.7 min ultrasound shock, and ultrasound frequency of 26.58 kHz, the highest amount of metabolite production was anticipated to be 215.19 mg/L. Overall, it was found that the actual values were consistent with the predicted values.

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.

Gamma-aminobutyric acid (GABA): a comprehensive review of dietary sources, enrichment technologies, processing effects, health benefits, and its applications

Gamma-aminobutyric acid (GABA) is a naturally occurring potential bioactive compound present in plants, microorganisms, animals, and humans. Especially, as a main inhibitory neurotransmitter in the central nervous system, GABA possesses a broad spectrum of promising bioactivities. Thus, functional foods enriched with GABA have been widely sought after by consumers. However, the GABA levels in natural foods are usually low, which cannot meet people's demand for health effects. With the increasing public awareness on the food securities and naturally occurring processes, using enrichment technologies to elevate the GABA contents in foods instead of exogenous addition can enhance the acceptability of health-conscious consumers. Herein, this review provides a comprehensive insight on the dietary sources, enrichment technologies, processing effects of GABA, and its applications in food industry. Furthermore, the various health benefits of GABA-enriched foods, mainly including neuroprotection, anti-insomnia, anti-depression, anti-hypertensive, anti-diabetes, and anti-inflammatory are also summarized. The main challenges for future research on GABA are related to exploring high GABA producing strains, enhancing the stability of GABA during storage, and developing emerging enrichment technologies without affecting food quality and other active ingredients. A better understanding of GABA may introduce new windows for its application in developing functional foods.

Influence of different lactic acid bacteria strains and milling process on the solid-state fermented green and red lentils (Lens culinaris L.) properties including gamma-aminobutyric acid formation

The aim of this study was to evaluate the influence of lactic acid bacteria (LAB) strains (Lactiplantibacillus plantarum No.122 and Lacticaseibacillus casei No.210) and milling process on the solid-state fermented (for 24 h, at 30°C) green and red lentils (Lens culinaris L.) properties, chiefly pH, LAB viable counts, color coordinates, free amino acid (FAA) profile, γ-aminobutyric acid (GABA) and biogenic amine (BA) concentrations, fatty acid (FA) and volatile compound (VC) profiles. Results showed that both of the tested LAB strains are suitable for the fermentation of lentils: pH of fermented lentils was <4.5 and LAB viable counts >8.0 log10 colony-forming units (CFU)/g. A very strong negative correlation was found (r = -0.973, p ≤ 0.0001) between LAB counts and pH of the samples. Also, fermentation and milling process were significant factors toward color coordinates of the lentils. In most of the cases, solid-state fermentation (SSF) increased essential FAA content in lentils; however, some of the non-essential FAA content was reduced. SSF significantly increased GABA concentration in lentils and milling process was a significant factor on GABA content of the samples (p ≤ 0.05). The main BA in lentils was spermidine, and SSF decreased their total BA content (34.8% on average in red lentils and 39.9% on average in green lentils). The main FA in lentils were linoleic and oleic. The main VC in lentils were hexanal, 1-hexanol, hexanoic acid, D-limonene and (E)-2-nonen-1-ol. Furthermore, most of the VC showed significant correlations with pH of lentil samples, LAB counts and FA content. Finally, the LAB strain used for fermentation and the milling process of lentils are significant factors for most of the analyzed parameters in lentil. Moreover, despite the higher GABA concentration found in green non-milled SSF lentils, application of combined milling and SSF is recommended because they showed the lowest BA content in addition to higher essential FAA and GABA concentrations.

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.

Changes of Bioactive Components and Antioxidant Capacity of Pear Ferment in Simulated Gastrointestinal Digestion In Vitro

Fruit ferment is rich in polyphenols, organic acids, enzymes, and other bioactive components, which contribute to their antioxidant ability. In this study, we investigated the effect of the simulated gastric and intestinal digestion in vitro on the total phenolic content (TPC), total flavonoid content (TFC), phenolic components content, organic acid content, protease activity, superoxide dismutase (SOD) activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (DPPH-RSA), hydroxyl (·OH) radical scavenging activity (·OH-RSA), and total reducing capacity in ‘Xuehua’ pear (Pyrus bretschneideri Rehd) ferment. The result showed that the TPC, TFC, protease activity, and phenolic components such as arbutin, protocatechuic acid, malic acid, and acetic acid showed a rising trend during the simulated gastric digestion in ‘Xuehua’ pear ferment, and these components might contribute to the increasing of ·OH-RSA and total reducing capacity. The SOD activity and epicatechin content showed an increasing trend at first and then a decreasing trend, which was likely associated with DPPH-RSA. During in vitro-simulated intestinal digestion, the majority of evaluated items reduced, except for protease activity, quercetin, and tartaric acid. The reason for the decreasing of bio-accessibility resulted from the inhibition of the digestive environment, and the transformation between substances, such as the conversion of hyperoside to quercetin. The correlation analysis indicated that the antioxidant capacity of ‘Xuehua’ pear ferment was mainly affected by its bioactive compounds and enzymes activity as well as the food matrices and digestive environment. The comparison between the digestive group with and without enzymes suggested that the simulated gastrointestinal digestion could boost the release and delay the degradation of phenolic components, flavonoids, and organic acid, protect protease and SOD activity, and stabilize DPPH-RSA, ·OH-RSA, and total reducing capacity in ‘Xuehua’ pear ferment; thus, the ‘Xuehua’ pear ferment could be considered as an easily digestible food.

Special tea products featuring functional components: Health benefits and processing strategies

The functional components in tea confer various potential health benefits to humans. To date, several special tea products featuring functional components (STPFCs) have been successfully developed, such as O-methylated catechin-rich tea, γ-aminobutyric acid-rich tea, low-caffeine tea, and selenium-rich tea products. STPFCs have some unique and enhanced health benefits when compared with conventional tea products, which can meet the specific needs and preferences of different groups and have huge market potential. The processing strategies to improve the health benefits of tea products by regulating the functional component content have been an active area of research in food science. The fresh leaves of some specific tea varieties rich in functional components are used as raw materials, and special processing technologies are employed to prepare STPFCs. Huge progress has been achieved in the research and development of these STPFCs. However, the current status of these STPFCs has not yet been systematically reviewed. Here, studies on STPFCs have been comprehensively reviewed with a focus on their potential health benefits and processing strategies. Additionally, other chemical components with the potential to be developed into special teas and the application of tea functional components in the food industry have been discussed. Finally, suggestions on the promises and challenges for the future study of these STPFCs have been provided. This paper might shed light on the current status of the research and development of these STPFCs. Future studies on STPFCs should focus on screening specific tea varieties, identifying new functional components, evaluating health-promoting effects, improving flavor quality, and elucidating the interactions between functional components.

Heat stress and excessive maturity of fruiting bodies suppress GABA accumulation by modulating GABA metabolism in Pleurotus ostreatus (Jacq. ex Fr.) P. Kumm

GABA is a health-promoting bioactive substance. Here, the GABA biosynthetic pathways were investigated, and then the dynamic quantitative changes in GABA and the expression levels of genes related to GABA metabolism under heat stress or at different developmental stages of fruiting bodies in Pleurotus ostreatus (Jacq. ex Fr.) P. Kumm were determined. We found that the polyamine degradation pathway was the main route of GABA production under growth normal condition. The accumulation of GABA and the expression of most genes related to GABA biosynthesis, including genes encoding glutamate decarboxylase (PoGAD-2), polyamine oxidase (PoPAO-1), diamine oxidase (PoDAO) and aminoaldehyde dehydrogenase (PoAMADH-1 and PoAMADH-2), were significantly suppressed by heat stress and the excessive maturity of fruiting bodies. Finally, the effects of GABA on the mycelial growth, heat tolerance and the morphogenesis and development of fruiting bodies were studied, the results showed that the deficiency of endogenous GABA inhibited the mycelial growth and primordial formation and aggravated heat damage, whereas exogenous application of GABA could improve thermotolerance and promote the development of fruiting bodies.

High Production of γ-Aminobutyric Acid by Activating the xyl Operon of Lactobacillus brevis

γ-Aminobutyric acid (GABA) is an inhibitory neurotransmitter with important physiological functions such as sleep assistance and anti-depression. In this study, we developed a fermentation process for the high-efficiency production of GABA by Lactobacillus brevis (Lb. brevis) CE701. First, xylose was found as the optimal carbon source that could improve the GABA production and OD₆₀₀ in shake flasks to 40.35 g/L and 8.64, respectively, which were 1.78-fold and 1.67-fold of the glucose. Subsequently, the analysis of the carbon source metabolic pathway indicated that xylose activated the expression of the xyl operon, and xylose metabolism produced more ATP and organic acids than glucose, which significantly promoted the growth and GABA production of Lb. brevis CE701. Then, an efficient GABA fermentation process was developed by optimizing the medium components using response surface methodology. Finally, the production of GABA reached 176.04 g/L in a 5 L fermenter, which was 336% higher than that in a shake flask. This work enables the efficient synthesis of GABA using xylose, which will provide guidance for the industrial production of GABA.

The molecular mechanism of γ-aminobutyric acid against AD: the role of CEBPα/circAPLP2/miR-671-5p in regulating CNTN1/2 expression

The expression levels of the synaptic-related proteins contactin 1/2 (CNTN1/2) are down-regulated in the brain of Alzheimer's disease (AD), but the mechanism has not been clarified. γ-Aminobutyric acid (GABA) is considered a biologically active ingredient in food. Our previous research revealed that GABA can regulate CEBPα expression in Aβ-treated U251 cells. However, it is uncertain whether GABA can antagonize the pathogenesis of AD. Whether GABA can inhibit the reduction in CNTN1/2 expression by regulating CEBPα/circAPLP2/miR-671-5p in the AD brain remains unclear yet. Here, we demonstrate that GABA could attenuate the deposition of Aβ in the brain and ameliorate cognitive impairments in AD model mice. The expressions of CEBPα, circAPLP2, and CNTN1/2 were decreased and that of miR-671-5p was increased in AD model mouse brains and Aβ-induced SH-SY5Y cells. These alterations were partly reversed by GABA. The CNTN1/2 expression was down-regulated and up-regulated in SH-SY5Y cells treated with miR-671-5p mimics and miR-671-5p inhibitors, respectively. The results from the luciferase reporter assay revealed that miR-671-5p could bind to the 3'-untranslated region of circAPLP2. The silencing of circAPLP2 with the siRNA duplex caused an up-regulation of miR-671-5p and a down-regulation of CNTN1/2 in SH-SY5Y cells. The silencing of CEBPα with the siRNA duplex caused a down-regulation of circAPLP2 or CNTN1/2 and an up-regulation of miR-671-5p. In conclusion, GABA may decrease the deposition of Aβ in the brain, inhibit the down-regulation of CNTN1/2 expression, and ameliorate the cognitive deficits of AD model mice. The CEBPα/circAPLP2/miR-671-5p pathway plays a role in regulating CNTN1/2 expression by GABA in AD.

Effects of fungal based bioactive compounds on human health: Review paper

Since the first years of history, microbial fermentation products such as bread, wine, yogurt and vinegar have always been noteworthy regarding their nutritional and health effects. Similarly, mushrooms have been a valuable food product in point of both nutrition and medicine due to their rich chemical components. Alternatively, filamentous fungi, which can be easier to produce, play an active role in the synthesis of some bioactive compounds, which are also important for health, as well as being rich in protein content. Therefore, this review presents some important bioactive compounds (bioactive peptides, chitin/chitosan, β-glucan, gamma-aminobutyric acid, L-carnitine, ergosterol and fructooligosaccharides) synthesized by fungal strains and their health benefits. In addition, potential probiotic- and prebiotic fungi were researched to determine their effects on gut microbiota. The current uses of fungal based bioactive compounds for cancer treatment were also discussed. The use of fungal strains in the food industry, especially to develop innovative food production, has been seen as promising microorganisms in obtaining healthy and nutritious food.

Exploring the Potential of Sustainable Acid Whey Cheese Supplemented with Apple Pomace and GABA-Producing Indigenous Lactococcus lactis Strain

This study aimed to utilize two by-products, acid whey and apple pomace, as well as an indigenous Lactococcus lactis LL16 strain with the probiotic potential to produce a sustainable cheese with functional properties. Acid whey protein cheese was made by thermocoagulation of fresh acid whey and enhancing the final product by adding apple pomace, L. lactis LL16 strain, or a mixture of both. The sensory, the physicochemical, the proteolytic, and the microbiological parameters were evaluated during 14 days of refrigerated storage. The supplementation of the cheese with apple pomace affected (p ≤ 0.05) the cheese composition (moisture, protein, fat, carbohydrate, and fiber), the texture, the color (lightness, redness, and yellowness), and the overall sensory acceptability. The addition of the presumptive probiotic L. lactis LL16 strain decreased (p ≤ 0.05) the concentration of glutamic acid, thus increasing γ-aminobutyric acid (GABA) significantly in the acid whey cheese. The supplementation with apple pomace resulted in slightly (p < 0.05) higher counts of L. lactis LL16 on day seven, suggesting a positive effect of apple pomace components on strain survival. The symbiotic effect of apple pomace and LL16 was noted on proteolysis (pH 4.6-soluble nitrogen and free amino acids) in the cheese on day one, which may have positively influenced the overall sensory acceptance.

Submerged and Solid-State Fermentation of Spirulina with Lactic Acid Bacteria Strains: Antimicrobial Properties and the Formation of Bioactive Compounds of Protein Origin

The aim of this study was to investigate the changes in bioactive compounds (L-glutamic acid (L-Glu), gamma-aminobutyric acid (GABA) and biogenic amines (BAs)) during the submerged (SMF) and solid-state (SSF) fermentation of Spirulina with lactobacilli strains (Lacticaseibacillus paracasei No. 244; Levilactobacillus brevis No. 173; Leuconostoc mesenteroides No. 225; Liquorilactobacillus uvarum No. 245). The antimicrobial properties of the untreated and fermented Spirulina against a variety of pathogenic and opportunistic strains were tested. The highest concentrations of L-Glu (3841 mg/kg) and GABA (2396 mg/kg) were found after 48 h of SSF with No. 173 and No. 244 strains, respectively. The LAB strain used for biotreatment and the process conditions, as well as the interaction of these factors, had statistically significant effects on the GABA concentration in Spirulina (p ≤ 0.001, p = 0.019 and p = 0.011, respectively). In all cases, the SSF of Spirulina had a higher total BA content than SMF. Most of the fermented Spirulina showed exceptional antimicrobial activity against Staphylococcus aureus but not against the other pathogenic bacteria. The ratios of BA/GABA and BA/L-Glu ranged from 0.5 to 62 and from 0.31 to 10.7, respectively. The GABA content was correlated with putrescine, cadaverine, histamine, tyramine, spermidine and spermine contents. The L-glutamic acid concentration showed positive moderate correlations with tryptamine, putrescine, spermidine and spermine. To summarize, while high concentrations of desirable compounds are formed during fermentation, the formation of non-desirable compounds (BAs) must also be considered due to the similar mechanism of their synthesis as well as the possibility of obtaining high concentrations in the end products.

Optimization of the hongqu starter preparation process for the manufacturing of red mold rice with high gamma-aminobutyric acid production by solid-state fermentation

Red mold rice (RMR) generally contains gamma-aminobutyric acid (GABA), which has several physiological functions. Monascus purpureus M162, with a high GABA production of 15.10 mg/g was generated by atmospheric and room temperature plasma mutation. Furthermore, we conducted a response surface methodology to produce a premium hongqu starter. The results revealed that under optimal conditions, that is, a substrate containing brown rice and bran in a brown rice: bran ratio of 9:1 (wt/wt), an inoculation size of 21.50 mL/100 g, a mixing frequency of one time/9 h, and a cultivation time of 7.20 days, the number of active spores, α-amylase activity, and saccharification power activity was 4.15 × 10⁷ spores/g, 155 U/g, and 3260 U/g in the high-quality starter, respectively. These values were 224.32-fold, 139.64%, and 141.74% higher than those obtained with M. purpureus M162 inoculated into steamed indica rice, respectively, and 153.70-fold, 267.24%, and 151.63% higher than those obtained with the parent strain M. purpureus M1, respectively. The premium hongqu starter of M. purpureus M162 was inoculated into steamed indica rice to produce RMR with 15.93 mg/g of GABA. In conclusion, we proposed a novel strategy for functional RMR production with high GABA concentrations by solid-state fermentation with Monascus spp.

Quantitative 1H NMR with global spectral deconvolution approach for the determination of gamma-aminobutyric acid in Chinese yam (Dioscorea polystachya Turczaninow)

We developed a quantitative proton nuclear magnetic resonance (qNMR) with global spectral deconvolution (GSD) method to determine the gamma-aminobutyric acid content in Chinese yam with the proton signal at δ_H 2.30. Trimethylsilyl-2,2,3,3-tetradeuteropropionic acid sodium salt was set as the internal standard. The method was validated and showed admissible stability, repeatability, and precision. Compared to the traditional high-performance liquid chromatography method, this method did not involve tedious pre-treatment and expensive standard. Compared to ordinary qNMR, GSD algorithm could effectively remove the effect of noise, baseline distortions and signal overlapping. Overall, qNMR with GSD method is a rapid, simple and reliable method to quantitatively determine functional metabolites even overlapped with other compounds in herbs or foods.

Chromosomal editing of Corynebacterium glutamicum ATCC 13032 to produce gamma-aminobutyric acid

Corynebacterium glutamicum has been used as a sustainable microbial producer for various bioproducts using cheap biomass resources. In this study, a high GABA-producing C. glutamicum strain was constructed by chromosomal editing. Lactobacillus brevis-derived gadB2 was introduced into the chromosome of C. glutamicum ATCC 13032 to produce gamma-aminobutyric acid and simultaneously blocked the biosynthesis of lactate and acetate. GABA transport and degradation in C. glutamicum were also blocked to improve GABA production. As precursor of GABA, l-glutamic acid synthesis in C. glutamicum was enhanced by introducing E. coli gdhA encoding glutamic dehydrogenase, and the copy numbers of gdhA and gadB2 were also optimized for higher GABA production. The final C. glutamicum strain CGY705 could produce 33.17 g/L GABA from glucose in a 2.4-L bioreactor after 78 h fed-batch fermentation. Since all deletion and expression of genes were performed using chromosomal editing, fermentation of the GABA-producing strains constructed in this study does not need supplementation of any antibiotics and inducers. The strategy used in this study has potential value in the development of GABA-producing bacteria.

Toward Sourdough Microbiome Data: A Review of Science and Patents

Technological prospecting was performed on documents related to sourdough microbiota using SCOPUS, Web of Science, Google Scholar, Espacenet and Patent Inspiration databases. Scientific articles and patents were analyzed based on three different perspectives: macro (year of publication, country, and institutions), meso (categorization as different taxonomies according to the subject evaluated), and micro (in-depth analysis of the main taxonomies, gathering the documents in subcategories). The main subject addressed in patents was the starter and product preparation, while 58.8% of the scientific publications focused on sourdough starter microbiota (identification and selection of microorganisms). Most patents were granted to companies (45.9%), followed by independent inventors (26.4%) and universities (21.8%). Sourdough products are in the spotlight when the subject is the bakery market; however, a closer integration between academia and industry is needed. Such a collaboration could generate a positive impact on the sourdough market in terms of innovation, providing a bread with a better nutritional and sensory quality for all consumers. Moreover, sourdough creates a new magnitude of flavor and texture in gastronomy, providing new functional products or increasing the quality of traditional ones.

Pleurotus eryngii Chips-Chemical Characterization and Nutritional Value of an Innovative Healthy Snack

Nowadays, as the pandemic has reshaped snacking behaviors, and consumers have become more health-conscious, the need for the incorporation of "healthy snacking" in our diets has emerged. Although there is no agreed-upon definition of "healthy snacking", dietary guidelines refer to snack foods with high nutritional and biological value. The aim of this study was to chemically characterize and determine the nutritional value of an innovative UVB-irradiated and baked snack from Pleurotus eryngii mushrooms. P. eryngii is an edible mushroom native to the Mediterranean basin. We applied proximate composition, amino acids, fatty acids, vitamins, and macro and trace elements analyses. Also, we computed indices to assess the nutritional quality of food, and we evaluated the sensory characteristics of the mushroom snack. We found high nutritional, consumer, and biological values for the snack. More specifically it was low in calories, high in fibre and protein, low in lipids, without added sugars, and high in ergosterol and beta-glucans. Additionally, it had some vitamins and trace elements in significant quantities. Its NRF9.3 score was considerably high compared to most popular snacks, and the snack exhibited high hypocholesterolemic and low atherogenic and thrombogenic potentials. In conclusion, as a result of UVB-irradiation and baking of P. eryngii mushrooms, the snack's nutritional and biological value were not affected; instead, it provided a "healthy snacking" option.

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.

Gamma-Aminobutyric Acid-Producing Levilactobacillus brevis Strains as Probiotics in Litchi Juice Fermentation

Levilactobacillus brevis strains can be isolated from traditional Chinese pickles and used as the starter cultures to improve the nutritional profiles of fermented juices. Three L. brevis strains (LBG-29, LBG-24, LBD−14) that produce high levels of gamma-aminobutyric acid (GABA; >300 mg/L) were isolated from traditional Chinese pickles. The strains showed tolerance to low pH and high bile salts and exhibited safety in vitro. Litchi juice was fermented using each strain at 37 °C for 48 h. The litchi juice was determined to be a good substrate for fermentation as the process enhanced its functional profile. Overall, cell vitality increased (above 8.7 log10 CFU/mL), the antioxidant activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric ion-reducing antioxidant power (FRAP) were significantly increased, and the antioxidant capacity of the 2,2′-amino-di(3-ethyl-benzothiazoline sulphonic acid-6)ammonium salt (ABTS) was decreased. There was also a significant increase in the GABA and acetic acid content after LBG-29 and LBG-24 fermentation. It was thus determined that the LBG-29 and LBG-24 strains could be used to improve beverage functionality and aid in the development of new products. This is the first report of litchi fermentation using L. brevis as a starter culture. Further research is required to elucidate the functional benefits for the human body and the nutritional and functional properties during its shelf life.

The Potential of Rhizobacteria to Mitigate Abiotic Stress in Lessertia frutescens

Lessertia frutescens is a multipurpose medicinal plant indigenous to South Africa. The curative ability of the medicinal plant is attributed to its rich phytochemical composition, including amino acids, triterpenoids, and flavonoids. A literature review of some of the phytochemical compounds, particularly amino acids, in L. frutescens shows a steady decrease in concentration over the years. The reduction of the phytochemical compounds and diminishing biological activities may be attributed to drought and salt stress, which South Africa has been grappling with over the years. Canavanine, a phytochemical which is associated with the anticancer activity of L. frutescens, reduced slightly when the plant was subjected to salt stress. Like other legumes, L. frutescens forms a symbiotic relationship with plant-growth-promoting rhizobacteria, which facilitate plant growth and development. Studies employing commercial plant-growth-promoting rhizobacteria to enhance growth and biological activities in L. frutescens have been successfully carried out. Furthermore, alleviation of drought and salt stress in medicinal plants through inoculation with plant growth-promoting-rhizobacteria is well documented and effective. Therefore, this review seeks to highlight the potential of plant-growth-promoting rhizobacteria to alleviate the effect of salt and drought in Lessertia frutescens.

Journey of the Probiotic Bacteria: Survival of the Fittest

This review aims to bring a more general view of the technological and biological challenges regarding production and use of probiotic bacteria in promoting human health. After a brief description of the current concepts, the challenges for the production at an industrial level are presented from the physiology of the central metabolism to the ability to face the main forms of stress in the industrial process. Once produced, these cells are processed to be commercialized in suspension or dried forms or added to food matrices. At this stage, the maintenance of cell viability and vitality is of paramount for the quality of the product. Powder products requires the development of strategies that ensure the integrity of components and cellular functions that allow complete recovery of cells at the time of consumption. Finally, once consumed, probiotic cells must face a very powerful set of physicochemical mechanisms within the body, which include enzymes, antibacterial molecules and sudden changes in pH. Understanding the action of these agents and the induction of cellular tolerance mechanisms is fundamental for the selection of increasingly efficient strains in order to survive from production to colonization of the intestinal tract and to promote the desired health benefits.

Changes in the physicochemical parameters and microbial community of a new cultivar blue wheat cereal wholemeal during sourdough production

Changes in the characteristics of a new cultivar (DS8472-5) of blue wheat during wholemeal fermentation with Pediococcus acidilactici (LUHS29), Liquorilactobacillus uvarum (LUHS245), and Lactiplantibacillus plantarum (LUHS122), including acidity, microbiological and chromaticity parameters, free amino acid (FAA), gamma-aminobutyric acid (GABA), and biogenic amine (BA) contents, macro- and micro-element concentrations and fatty acid (FA) and volatile compounds (VC), were evaluated. In addition, a metagenomic analysis was performed. The lactic acid bacteria (LAB) strains used for fermentation was a significant factor in wholemeal fermentation sample pH, redness (a*) and LAB counts (p ≤ 0.05). In most of the samples, fermentation increased the FAA content in wheat wholemeal, and the highest concentration of GABA was found in DS8472-5 LUHS122 samples. Phenylethylamine (PHE) was found in all wheat wholemeal samples; however, spermidine was only detected in fermented samples and cadaverine only in DS8472-5 LUHS122. Fermented samples showed higher omega-3 and omega-6 contents and a higher number and variety of VC. Analysis of the microbial profile showed that LAB as part of the natural microbiota present in cereal grains also actively participates in fermentation processes induced by industrial bacterial cultures. Finally, all the tested LAB were suitable for DS8472-5 wheat wholemeal fermentation, and the DS8472-5 LUHS122 samples showed the lowest pH and the highest LAB viable counts (3.94, 5.80°N, and 8.92 log10 CFU/g, respectively).

The Production of γ-Aminobutyric Acid from Free and Immobilized Cells of Levilactobacillus brevis Cultivated in Anaerobic and Aerobic Conditions

γ-aminobutyric acid (GABA) has several beneficial effects on human health. GABA may be produced via chemical synthesis or through microbial metabolism, and Levilactobacillus brevis is recognized as a GABA-producing species. In this study, 11 Lvb. brevis strains were screened for GABA production, and the best producers were selected to verify the effect of aerobic (AE) and respiratory (RS) cultivations on growth parameters, biomass, and GABA accumulation. Lvb. brevis LB12 was then used to evaluate the combined effect of the incubation atmosphere (anaerobiosis vs. aerobiosis), cell protection (free vs. immobilized cells), and cell recycling (fresh vs. starved cells) on GABA production. Glutamate (GLU) consumption and GABA accumulation were detected by Thin-layer Chromatography (TLC) and RP-HPLC analyses. The ability to produce GABA was widespread among the strains. AE and RS growth improved biomass production, but oxygen availability impaired GLU to GABA conversion, and the anaerobically growing cells had the highest GABA productivity. Immobilized strains had lower efficiency in both GLU uptake and conversion compared to free cells, probably due to the poor diffusion in alginate beads. The use of resting cells allowed further GABA production without the cultivation step, but cell activity was exhausted after three cycles of reutilization. Lvb. brevis LB12 is an excellent GABA producer, and AE cultivation can be exploited to improve the final cell density; however, the conditions for boosting GLU to GABA conversion and cell regeneration need to be further investigated.