Gamma-aminobutyric acid (GABA) is a non-protein amino acid playing a significant role in the central nervous system and the gut–brain axis. This study investigated the potential to produce GABA by lactic acid bacteria (LAB) isolated from different varieties of organic tomatoes. The isolated LAB were taxonomically identified by 16S rRNA gene sequencing, the presence of the gadB gene (glutamate decarboxylase) was detected, and GABA production was quantified using HPLC. Levilactobacillus brevis CRAI showed the highest GABA production under optimised fermentation conditions with 4% monosodium glutamate (MSG). The genome sequencing of L. brevis CRAI revealed the presence of gadA and gadB isoforms and assessed the strain’s safety profile. The gene expression analysis revealed that the gadA and gadB genes were upregulated in the presence of 4% MSG. The probiotic potential of L. brevis CRAI was also assessed by functional assays. The strain showed strong antimicrobial activity against representative enteropathogens, i.e., Escherichia coli ETEC, Salmonella choleraesuis, and Yersinia enterocolitica, and anti-inflammatory effect, reducing nitric oxide production in LPS-stimulated RAW264.7 macrophages. In addition, its ability to adhere to intestinal epithelial Caco-2 cells was demonstrated. These results highlight L. brevis CRAI as a promising candidate for the development of GABA-enriched functional foods or probiotic supplements with the perspective to modulate the gut-brain axis.

Background/Objectives: Due to the high frequency and severity of upper respiratory bacterial infections, probiotics could offer a new medical approach. We explored the antibacterial and anti-inflammatory properties of the new strain Lactiplantibacillus plantarum BIA and formulated a nasal spray. Methods: L. plantarum BIA was isolated from orange peel and taxonomically identified through 16S rRNA gene sequencing. Its antibacterial activity was tested against Pseudomonas aeruginosa, Streptococcus pyogenes, Bacillus subtilis, Escherichia coli, and Staphylococcus aureus, while anti-inflammatory potential was evaluated by Griess assay. BIA genome was fully sequenced and analyzed to assess its safety. BIA was formulated in a freeze-dried matrix, containing prebiotics and cryoprotectants, to be reconstituted with a polymer solution. Solutions containing two types of hydroxypropyl methylcellulose (HPMC) and hyaluronic acid were evaluated as resuspending media and compared in terms of pH, viscosity, and mucoadhesion ability. The biological activity of BIA formulated as nasal spray was verified together with the stability of the selected formulations. Results: L. plantarum BIA inhibited human pathogens’ growth and showed anti-inflammatory activity and a safe profile. In the best-performing formulation, the probiotic is lyophilized in 10% fructooligosaccharides, 0.1% ascorbic acid, and 0.5% lactose and reconstituted with HPMC high viscosity 1% w/v. This composition ensured the probiotic’s viability for up to six months in its dried form and one week after reconstitution. It also allowed interaction with the nasal mucosa, preserving its antimicrobial and anti-inflammatory activities. Conclusion: The developed nasal spray could become a promising formulation in the field of nasal infectious and inflammatory diseases.