Gamma-aminobutyric acid-producing abilities of lactococcal strains isolated from old-style cheese starters

A previous study showed the ability of old-style cheese starters to produce large amounts of γ-aminobutyric acid (GABA). This work reports the identification of GABA-producing strains and the effect of the main cheese matrix parameters (NaCl, glutamic acid, pH, oxygen) having an influence on GABA production. Out of a total of 50 individual bacterial strains contained in two old-style cheese starters, nine were able to produce GABA and were identified as either Lactococcus lactis ssp. lactis or L. lactis ssp. lactis biovar diacetylactis. Strains ULAAC-A13 and ULAAC-A23 were able to produce up to 500 mg of GABA per 100 mL of fermented milk containing 2% NaCl and 367 mg per 100 mL of glutamate. Moreover, the low residual glutamate concentration indicates the almost total conversion of glutamate into GABA. GABA was also detected in four commercial cheeses at concentrations varying from 10 to 97 mg of GABA per 30 g of cheese and at a concentration of 29 mg of GABA per 30 g of a cheese slurry ripened with ULAAC-A old-style starter. In that cheese slurry, GABA concentrations were above the levels previously proven to be effective for lowering blood pressure in humans. Both individual GABA-producing strains or the old-style starters containing the GABA strains seem to be promising for GABA production in hard or semi-hard cheeses with prevailing conditions for GABA production.