Optimization of γ-aminobutyric acid production with levilactobacillus brevis AK19B strain

In this study, genetic identification of Levilactobacillus brevis AK19B strain isolated from sourdough dough and identified phenotypically was made and γ-aminobutyric acid (GABA) production was optimized by examining its techno-functional properties. The strain showed good antimicrobial activity against Escherichia coli BC 1402, Salmonella typhimurium RSSK 95091 and Yersinia enterocolitica ATCC 27729 and antifungal activity against molds by spot culture method. The isolate grew very well at 25 ℃ and poorly at 45 ℃, but failed at 4 ℃. The isolate, which showed very good growth at pH 5 and pH 8, showed better growth in the medium containing 7% NaCl than in the medium containing 10% and 15% NaCl. L. brevis AK19B strain was characterized as a non-thermotolerant, hydrophilic LAB strain with phytase enzyme activity. In addition, it has been determined that it can maintain its vitality for a certain period of time and exhibit antioxidant activity in environments containing bile salt. It was determined that L. brevis AK19B did not show resistance to streptomycin, ampicillin, erythromycin, tetracycin, penicillin, kanamycin and chloramphenicol. In the study, the optimization of the monosodium glutamate concentration (MSG), NaCl concentration, temperature and pH independent variables used in GABA production according to the Box-Behnken experimental design was carried out using the Design-Expert package program. As a result of the experiments suggested by the design, models expressing the effects of independent variables on the responses were created and the suitability of the models was evaluated by analysis of variation (ANOVA). As a result of the data obtained, optimum conditions range from 4-8 for pH, incubation temperature 25-40 ℃, MSG concentration 100-300 mM and for NaCl concentration 0-4 mM. As a result of the experiments, it was determined that the independent variables had different effects on GABA production. Based on the ANOVA and RSM model statistics, it has been shown that the quadratic model is more suitable for GABA production and the model (p<0.001) is important. For maximum GABA production, optimum production conditions of pH 5.136, MSG concentration of 297, temperature of 26 and NaCl concentration of 2.82 were applied, and GABA production was estimated as 43.85 mg/mL.