Abstract:In order to obtain lactic acid bacteria within food safety level, which is needed for preparing gamma-aminobutyric acid (GABA)-rich yogurt from dairy-based substrates, 171 lactic acid bacterial strains were isolated from fermented food in domestic market as tested strains. Species identification of these strains was conducted by 16S rDNA sequence analysis, and GABA yield after-fermentation was determined by improved HPLC. After primary screening in broth medium and rescreening in dairy-based medium, one strain of Lactococcus Lactis subsp. lactis (No.4043) was obtained, which had high-yield potential of GABA in dairy-based medium. Inoculated into 10% (W/V) skimmed reconstituted milk with sodium L-glutamate of 2 g/L, the yield of GABA was about 0.39 g/L after fermenting by single strain at 30 ℃ for 48 h, which ranked relatively high level at present. 18 kinds of sugars such as glucose, galactose, etc., couldbe metabolizedby strain No.4043.Inoculated intoM17 medium at 30 ℃, the logarithmic growth period was 2~8 h. The strain No.4043 was weak in continuous acid-producing capacity, showed good acid tolerance in the environment with pH 3~5.5, good in auto-aggregation but poor in bile salt tolerance.Surface hydrophobicity and adhesion of the strain No.4043 were weak, leading to difficulties in adhering and colonizing in human intestinal effectively, which was not suitable to be probiotics in gastrointestinal tract. The strain No.4043 could be used as a starter for producing yoghurt rich in GABA by mixed fermentation of multiple strains.
