Selection of GABA-Producing Lactic Acid Bacteria Strains by Polymerase Chain Reaction Using Novel gadB and gadC Multispecies Primers for the Development of New Functional Foods

Gamma-aminobutyric acid (GABA) has been attributed to health-promoting properties and has received attention from the food industry as an attractive bioactive compound for the development of functional foods. Some lactic acid bacteria (LAB) produce GABA through a glutamate decarboxylase encoded by <i>gad</i>B and a glutamate/GABA antiporter encoded by <i>gad</i>C. In this study, we develop a molecular screening method based on a polymerase chain reaction able to detect those genes in different LAB species through the use of novel multispecies primers. PCR was performed in 92 LAB strains of six different species. The primer pair designed for <i>gad</i>B allowed its identification in <i>Lactiplantibacillus plantarum</i>, <i>Lactococcus cremoris</i>, <i>Lactococcus lactis</i>, <i>Levilactobacillus brevis</i>, <i>Limosilactobacillus fermentum</i>, and <i>Limosilactobacillus reuteri</i> strains. For <i>gad</i>C, two different primer pairs were designed for its detection in different species. Glutamate decarboxylase activity (GAD assay) and GABase enzymatic quantification were also assessed. Among those strains showing glutamate decarboxylase activity, 93.2% harbored the <i>gad</i>B gene, and those showing GABA production had the <i>gad</i>B gene and exhibited glutamate decarboxylase activity. PCR detection of <i>gad</i>B correlates strongly with GABA production and constitutes a good strategy for the selection of LAB with high yields (>18 mM) that could be used for the development of GABA-enriched functional foods.