Fig. 2

Microbial GABA production and glutamate utilization by Levilactobacillus brevis strains. GABA and glutamate are measured from cell free culture supernatants by liquid chromatography–mass spectrometry and are expressed in units of μg/mL. Limit of detection (LOD) for quantitation of GABA is 50 μg/mL and for glutamate is 100 μg/mL. Symbols are further explain un-der each graph type. A–C GABA (teal and l-glutamic acid (blue) measured in the culture supernatants (right y-axis) at each of the timepoints (x-axis) during growth (OD at 600 nm on the right hand y-axis) of the L. brevis strains Lbr-6108 (B), Lbr-35 (C) and ATCC 14869 (D) in MRS media without (dotted lines and open symbols) and with 10,000 μg/mL monosodium glutamate (MSG) (solid lines and closed symbols). D Growth curve of all L. brevis strains in MRS media with and without 10,000 μg/mL MSG for comparison. E GABA production over time when Lbr-6108 was grown in MRS media supplemented with 10,000 μg/mL, 30,000 μg/mL or 90,000 μg/mL of MSG. The bar graph represents GABA production (left y-axis) in µg/mL of GABA produced, while the black diamonds shows the percent of yield (calculated as GABA μg/mL/glutamate utilization μg/mL) (right y-axis). Error bars may be obscured by symbols and boxes