Isolation of γ-aminobutyric acid-producing bacteria and optimization of fermentative medium

Ten gamma-aminobutyric acid (GABA)-producing lactic acid bacteria (LAB) strains were isolated from kimchi and yoghurt. The strain B, isolated from kimchi showed the highest GABA-producing ability (3-68g/L) in MRS broth with 1% monosodium glutannate (MSG). Strain B was identified as Lactococcus lactis subsp. lactis. The GABA-producing ability of L. lactisBwas investigated using brown ricejuice, germinated soybean juice and enzymolyzed skim milkas medium cornpositions.The D-optimal mixture design was applied to optimize theratioofthe threekinds ofcomponents in themedia.The resultsshowed thatwhen the mixing ratio of brown rice juice, germinated soybean juice and enzymolyzed skim milk was 33:58:9 (v:v:v), the maximum GABA yield of L. lactis B was 6.41 g/L. (c) 2008 Elsevier B.V. All rights reserved.