Enzyme-based microtiter plate assay for γ-aminobutyric acid:: Application to the screening of γ-aminobutyric acid-producing lactic acid bacteria

An enzyme-based microliter plate assay for gamma-aminobutyric acid (GABA) was developed. GABA was quantified using gamma-aminobutyrate glutamate aminotransferase and succinic semialdehyde dehydrogenase in the presence of NADP(+) and a-ketoglutarate. The NADPH produced by the series of enzymatic reactions was measured spectrophotometrically at 340 nm. A linear relationship between absorbance and the concentration of GABA was obtained in the ranges from 5.0 x 10(-4) to 1.0 x 10(-2) M. The relative standard deviation for 10 successive measurements was 0.9% at the 10 mM GABA level. This analytical method was applied to the screening of GABA-producing lactic acid bacteria in de Man-Rogosa-Sharpe (MRS) medium. The proposed method enables one to assay 96 samples for an hour without the pre-treatment of samples. The method is by far superior to the traditional HPLC method from the point of view of rapidity and simplicity. (c) 2005 Elsevier B.V. All rights reserved.