Gabase from pseudomonas fluorescens

Intracellular GABA (GABA_i) and extracellular GABA (GABA_e), were measured as previously described [17] (link), [19] (link). Cultures were grown to mid-exponential phase (OD₆₀₀ = 0.35) or stationary phase (16 h) at 37°C with aeration in BHI medium. For exponential phase GABA measurements the cultures were reduced to pH 4.0, while for stationary phase GABA measurements, the pH of the cultures was lowered to 4.0 (EGDm) or 3.5 (10403S) with 3 M HCl. Different pH reductions for each strain were necessary to ensure optimal GABA production for each strain. Extractions were made after 1 h of acid treatment. Non HCl-treated cultures were used as negative controls. GABase from Pseudomonas fluorescens (Sigma Aldrich, Steinheim, Germany) was used in the enzymatic assay and increases in OD_{340 nm} were measured using a Tecan Sunrise absorbance plate reader.