Background and objective: Lactic acid bacteria (LAB) is of interest in food fermentation studies. Gamma Amino Butyric Acid (GABA) is one of bioactive metabolites produced by LAB that pose significant impact on human health. At this study, we isolated the probiotic bacteria from Iranian traditional dairy products, identified them, and evaluated their potential in GABA production.
Materials and methods: In this research, 30 isolates of bacteria from traditional dairies (yogurt, dough, cheese and butter) were studied. To diagnose probiotic species, initial tests including gram staining, oxidase and catalase were performed. Additional verification studies on the approved isolated bacteria in the last step were included to acid, bile and pepsin and trypsin resistance, hemolysis inactivity and L-arginine hydrolysis. Probiotic bacteria were characterized by 16SrDNA PCR approach. In addition, GABA concentration was detected by HPLC equipped with C18 column (150 mm× 4.6 mm × 0.5 µm) at 25°C and UV-VIS detector (λ = 338 nm). The mobile phases of sodium dihydroxy phosphate and acetonitrile/ methanol/water were used in gradient mode.

Results and conclusion: Among all isolated bacteria, six strains were gram-positive, catalase-negative and oxidase-negative that initially known as LAB. Two out of six LAB isolates with acceptable probiotic characteristics were selected based on supplementary tests. Accordingly, Lactobacillus lactis ssp. Lactis and Lactobacillus delbrueckii ssp. Bulgaricus isolated from cheese and butter, respectively, showed the most significant probiotic properties. However, Lactobacillus delbrueckii ssp. Bulgaricus produced higher GABA than another (377.54 vs. 301.09 mg l^-1). As conclusion, traditional dairies in Iran are good reservoir of indigenous healthy microorganisms that can be used as starter or adjuvant culture with several helpful impacts on consumers.