Isolation and Characterization of Levilactobacillus brevis FBL-3 from Godeulppaegi Kimchi and Screening of Medium Components for γ-Aminobutyric Acid Production.

γ-Aminobutyric acid (GABA) is an amino acid with a variety of biological functions and is now becoming an essential food ingredient. In this work, a GABA-producing lactic acid bacterium was isolated from godeulppaegi kimchi and characterized by phenotypic, biochemical and molecular parameters. The isolate was identified as FBL-3, which produced acid colonies in MRS agar containing CaCO3 and L-glutamic acid, was Gram positive, catalase-negative and rod-shaped, and had 99.1% similarity to Levilactobacillus brevis by API 50 CHL analysis and 100% 16S rRNA gene sequence similarity to Lvb. brevis ATCC 14869. Further, sequence analysis of 16S rRNA gene confirmed that it was Lvb. brevis FBL-3. The effects of carbon source, nitrogen source, and L-glutamic acid concentration on cell growth and TLC-densitometrically estimated GABA production were evaluated sequentially using a one-factor-at-a-time approach. Of the carbon sources tested, xylose had the highest GABA production (12.2 ± 2.34 g/L) and dry cell weight (0.75 ± 0.00 g/L) and 10 g/L xylose was selected as a good concentration for GABA production. Yeast extract was the most promising for nitrogen sources producing 4.65 ± 0.45 g/L GABA, and 20 g/L yeast extract was selected as a practical concentration since it produced 9.12 ± 1.48 g/L GABA with lower nitrogen input than 50 g/L yeast extract. L-Glutamic acid was a necessary precursor to GABA production. Although the highest GABA titer in the L-glutamic acid concentration experiment was found for 50 g/L L-glutamic acid (19.6 ± 1.03 g/L), 10 g/L L-glutamic acid supported the highest cell growth and was considered as a more balanced precursor.