Production of γ-aminobutyric acid (GABA) by lactic acid bacteria strains isolated from traditional, starter-free dairy products made of raw milk

VALENZUELA JOSE ; FLOREZ ANA; VAZQUEZ LUCIA; VASEK, OLGA M.; MAYO BALTASAR

Beneficial Microbes

Wageningen Academic Publishers

Año: 2019

γ-Aminobutyric acid (GABA), an amino acid not used in protein synthesis, intervenes in several physiological functions and has both diuretic and calming effects in humans. Lactic acid bacteria (LAB) strains that produce GABA could be exploited for the manufacture of health-promoting GABA-enriched dairy products. In this study, 262 LAB strains isolated from traditional dairy products made from raw milk without starter cultures were screened for GABA production in culture media supplemented with 1% monosodium glutamate (MSG) using an enzymatic (GABase) method. About half of the strains (123) were found to be GABA producers. Of these, 24, among which were 16 Lactococcus lactis subsp. lactis and three Streptococcus thermophilus strains, produced >1 mM (range 1.01-2.81 mM) of GABA and were selected for further characterization. GABA production was confirmed in most strains by culturing in 5 mM MSG followed by HPLC quantification, although lower production levels were recorded by the latter method. Using species-specific primers, the gene encoding glutamate decarboxylase(GAD) was PCR-amplified in all but one of 21 of the GABA producers analysed. Amplicons sequences were compared to one another and to those held in databases. Except for one Lactobacillus brevis strain, none of the 24 GABA producers investigated produced toxic biogenic amines, such as tyramine, histamine or cadaverine. They were therefore considered safe. Either alone, in mixtures, or in combination with industrial starter and adjunct cultures, these strains might be useful in the development of health-orientated dairy products.