High-yield gamma-aminobutyric acid synthesis by wild-type Levilactobacillus brevis strains isolated from traditional Iranian Kashk.

aimsGamma-aminobutyric acid (GABA) is a principal inhibitory neurotransmitter involved in neuronal excitability, relaxation, anxiety modulation, and gut-brain axis regulation. Lactic acid bacteria (LAB), as prolific microbial producers of GABA, are prime candidates for developing psychobiotic and functional foods due to their generally recognized as safe (GRAS) status and health-promoting properties. This study aimed to isolate and identify novel wild-type, high GABA-producing LAB from the traditional Iranian fermented dairy product Kashk. METHODS AND

resultsA total of 33 Kashk samples, comprising 28 indigenous/artisanal and 5 commercial samples, were collected from Isfahan province. From the 28 indigenous/artisanal samples, 33 Gram-positive, catalase-negative LAB isolates were recovered. GABA production was quantified in a medium containing 5% monosodium glutamate using paper chromatography coupled with spectrophotometry. Eight isolates exhibiting GABA yields above 10 g/L (11.2-26.6 g/L) were selected for further study. 16 S rRNA gene sequencing identified all eight isolates (K-Isf 2, 8, 11, 12, 16, 25, 27, and 28) as Levilactobacillus brevis, exhibiting notable intraspecies variation in GABA biosynthesis. Phylogenetic analysis placed most isolates within a cohesive Levilactobacillus brevis cluster, whereas isolate 28 represented a divergent lineage. All high-performing isolates originated from cow's milk Kashk.

conclusionsThe identified thermotolerant Levilactobacillus brevis strains exhibit high intrinsic GABA biosynthetic capacity and significant intraspecies variability, making them valuable candidates for biotechnological exploitation. IMPACT STATEMENT: These novel Levilactobacillus brevis strains from traditional Kashk underline the potential of native Iranian fermented foods as reservoirs of psychobiotic microorganisms. Their strong GABA-producing performance positions them as promising functional starter cultures for developing antihypertensive and anti-stress fermented products.