Characterization and immobilization on nickel-chelated Sepharose of a glutamate decarboxylase A from Lactobacillus brevis BH2 and its application for production of GABA

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.

Synthesis of versatile neuromodulatory molecules by a gut microbial glutamate decarboxylase

Dysbiosis of the microbiome correlates with many neurological disorders, yet very little is known about the chemistry that controls the production of neuromodulatory molecules by gut microbes. Here, we found that an enzyme glutamate decarboxylase (BfGAD) of a gut microbe Bacteroides fragilis forms multiple neuromodulatory molecules such as γ-aminobutyric acid (GABA), hypotaurine, taurine, homotaurine, and β-alanine. We evolved BfGAD and doubled its taurine productivity. Additionally, we increased its specificity towards the substrate L-glutamate. Here, we provide a chemical strategy via which the BfGAD activity could be fine-tuned. In future, this strategy could be used to modulate the production of neuromodulatory molecules by gut microbes.

Recent advances in microbial production of diamines, aminocarboxylic acids, and diacids as potential platform chemicals and bio-based polyamides monomers

Recently, bio-based manufacturing processes of value-added platform chemicals and polymers in biorefineries using renewable resources have extensively been developed for sustainable and carbon dioxide (CO₂) neutral-based industry. Among them, bio-based diamines, aminocarboxylic acids, and diacids have been used as monomers for the synthesis of polyamides having different carbon numbers and ubiquitous and versatile industrial polymers and also as precursors for further chemical and biological processes to afford valuable chemicals. Until now, these platform bio-chemicals have successfully been produced by biorefinery processes employing enzymes and/or microbial host strains as main catalysts. In this review, we discuss recent advances in bio-based production of diamines, aminocarboxylic acids, and diacids, which has been developed and improved by systems metabolic engineering strategies of microbial consortia and optimization of microbial conversion processes including whole cell bioconversion and direct fermentative production.

Enzyme Immobilization and Co-Immobilization: Main Framework, Advances and Some Applications

Enzymes are outstanding (bio)catalysts, not solely on account of their ability to increase reaction rates by up to several orders of magnitude but also for the high degree of substrate specificity, regiospecificity and stereospecificity. The use and development of enzymes as robust biocatalysts is one of the main challenges in biotechnology. However, despite the high specificities and turnover of enzymes, there are also drawbacks. At the industrial level, these drawbacks are typically overcome by resorting to immobilized enzymes to enhance stability. Immobilization of biocatalysts allows their reuse, increases stability, facilitates process control, eases product recovery, and enhances product yield and quality. This is especially important for expensive enzymes, for those obtained in low fermentation yield and with relatively low activity. This review provides an integrated perspective on (multi)enzyme immobilization that abridges a critical evaluation of immobilization methods and carriers, biocatalyst metrics, impact of key carrier features on biocatalyst performance, trends towards miniaturization and detailed illustrative examples that are representative of biocatalytic applications promoting sustainability.

Food-grade γ-aminobutyric acid production by immobilized glutamate decarboxylase from Lactobacillus plantarum in rice vinegar and monosodium glutamate system

OBJECTIVES

γ-amino butyric acid (GABA) is a non-protein amino acid, considered a potent bioactive compound. This study focused on biosynthesis of food-grade GABA by immobilized glutamate decarboxylase (GAD) from Lactobacillus plantarum in the rice vinegar and monosodium glutamate (MSG) reaction system.

RESULTS

The gene encoding glutamate decarboxylase (GadB) from L. plantarum has been heterologously expressed in Lactococcus lactis and biochemically characterized. Recombinant GadB existed as a homodimer, and displayed maximal activity at 40 °C and pH 5.0. The K_m value and catalytic efficiency (k_cat/K_m) of GadB for L-Glu was 22.33 mM and 62.4 mM^-1 min^-1, respectively, with a specific activity of 24.97 U/mg protein. Then, purified GadB was encapsulated in gellan gum beads. Compared to the free enzyme, immobilized GadB showed higher operational and storage stability. Finally, 9.82 to 21.48 g/L of GABA have been acquired by regulating the amounts of catalyst microspheres ranging from 0.5 to 0.8 g (wet weight) in 0.8 mL of the designed rice vinegar and MSG reaction system.

CONCLUSIONS

The method of production GABA by immobilized GadB microspheres mixed in the rice vinegar and MSG reaction system is introduced herein for the first time. Especially, the results obtained here meet the increased interest in the harnessing of biocatalyst to synthesize food-grade GABA.

Genome Sequence of Lactobacillus plantarum KB1253, a Gamma-Aminobutyric Acid (GABA) Producer Used in GABA-Enriched Tomato Juice Production

Here, we present the draft genome sequence of Lactobacillus plantarum KB1253, isolated from a traditional Japanese pickle. Its genome comprises 3,097 genes and 3,305,456 nucleotides, with an average G+C content of 44.4%.

Here, we present the draft genome sequence of Lactobacillus plantarum KB1253, isolated from a traditional Japanese pickle. Its genome comprises 3,097 genes and 3,305,456 nucleotides, with an average G+C content of 44.4%.

Biotechnological advances and perspectives of gamma-aminobutyric acid production

Gamma-aminobutyric acid (GABA) is a four-carbon non-protein amino acid that is widely distributed among various organisms. Since GABA has several well-known physiological functions, such as mediating neurotransmission and hypotensive activity, as well as having tranquilizer effects, it is commonly used as a bioactive compound in the food, pharmaceutical and feed industries. The major pathway of GABA biosynthesis is the irreversible decarboxylation of L-glutamate catalyzed by glutamate decarboxylase (GAD), which develops a safe, sustainable and environmentally friendly alternative in comparison with traditional chemical synthesis methods. To date, several microorganisms have been successfully engineered for high-level GABA biosynthesis by overexpressing exogenous GADs. However, the activity of almost all reported microbial GADs sharply decreases at physiological near-neutral pH, which in turn provokes negative effects on the application of these GADs in the recombinant strains for GABA production. Therefore, ongoing efforts in the molecular evolution of GADs, in combination with high-throughput screening and metabolic engineering of particular producer strains, offer fascinating new prospects for effective, environmentally friendly and economically viable GABA biosynthesis. In this review, we briefly introduce the applications in which GABA is used, and summarize the most important methods associated with GABA production. The major achievements and present challenges in the biotechnological synthesis of GABA, focusing on screening and enzyme engineering of GADs, as well as metabolic engineering strategy for one-step GABA biosynthesis, will be extensively discussed.

Purification and characterization of glutamate decarboxylase from Enterococcus raffinosus TCCC11660

Glutamate decarboxylase (GAD) is the sole enzyme that synthesizes γ-aminobutyric acid through the irreversible decarboxylation of L-glutamate. In this study, the purification and characterization of an unreported GAD from a novel strain of Enterococcus raffinosus TCCC11660 were investigated. The native GAD from E. raffinosus TCCC11660 was purified 32.3-fold with a recovery rate of 8.3%, using ultrafiltration and ammonium sulfate precipitation, followed by ion-exchange and size-exclusion chromatography. The apparent molecular weight of purified GAD, as determined by SDS-PAGE and size-exclusion chromatography was 55 and 110 kDa, respectively, suggesting that GAD exists as a dimer of identical subunits in solution. In the best sodium citrate buffer, metal ions of Mo⁶⁺ and Mg²⁺ had positive effects, while Cu²⁺, Fe²⁺, Zn²⁺ and Co²⁺ showed significant adverse effects on enzyme activity. The optimum pH and temperature of GAD were determined to be 4.6 and 45 °C, while the K _m and V _max values for the sole L-glutamate substrate were 5.26 and 3.45 μmol L^-1 min^-1, respectively.

Genome Sequence of Lactobacillus curieae CCTCC M 2011381T, a Novel Producer of Gamma-aminobutyric Acid

Lactobacillus curieae CCTCC M 2011381(T) is a novel species of the genus Lactobacillus and a gamma-aminobutyric acid producer that was isolated from stinky tofu brine. Here, we present a 2.19-Mb assembly of its genome, which may provide further insights into the molecular mechanisms underlying its beneficial properties.