Metabolome analysis of milk fermented by γ-aminobutyric acid–producing Lactococcus lactis

Abstract

γ-Aminobutyric acid (GABA) is one of the most important functional components in fermented foods because of its physiological functions, such as neurotransmission and antihypertensive activities. However, little is known about components other than GABA in GABA-rich fermented foods. A metabolomic approach offers an opportunity to discover bioactive and flavor components in fermented food. To find specific components in milk fermented with GABA-producing Lactococcus lactis 01-7, we compared the components found in GABA-rich fermented milk with those found in control milk fermented without GABA production using capillary electrophoresis time-of-flight mass spectrometry. A principal component analysis score plot showed a clear differentiation between the control milk fermented with L. lactis 01-1, which does not produce GABA, and GABA-rich milk fermented with a combination of L. lactis strains 01-1 and 01-7. As expected, the amount of GABA in GABA-rich fermented milk was much higher (1,216-fold) than that of the control milk. Interestingly, the amount of Orn was also much higher (27-fold) than that of the control milk. Peptide analysis showed that levels of 6 putative angiotensin-I-converting enzyme (ACE)-inhibitory peptides were also higher in the GABA-rich fermented milk. Furthermore, ACE-inhibitory activity of GABA-rich fermented milk tended to be higher than that of the control milk. These results indicate that the GABA-producing strain 01-7 provides fermented milk with other functional components in addition to GABA.

Characterization of unique metabolites in γ‐aminobutyric acid‐rich cheese by metabolome analysis using liquid chromatography‐mass spectrometry

“…The amount of glutamate in the GABA‐rich cheese was 0.143‐fold lower than that in the control cheese. This is because glutamate is converted to GABA by the glutamate decarboxylase enzyme (Hagi et al, ). In addition, the amount of arginine in the GABA‐rich cheese (247.87 nmol/g) was also 0.42‐fold lower than that in the control cheese (591.47 nmol/g).…”

“…lactis subsp. cremoris 01‐1 strains which were also used in our previous study (Hagi et al, ). Both strains were grown at 30°C for 48 hr in 300 ml of skim milk.…”

“…The angiotensin‐converting enzyme (ACE) inhibitory activity of peptides derived from yogurt (fermented milk) and cheese has been frequently investigated (Gómez‐Ruiz, Ramos, & Recio, ; Hagi, Kobayashi, & Nomura, ). In addition, peptides with antioxidative, anti‐inflammatory, and anxiolytic activities derived from milk protein have been reported (Conway, Gauthier, & Pouliot, ; Marcone, Haughton, Simpson, Belton, & Fitzgerald, ; Mizushige, Sawashi, Yamada, Kanamoto, & Ohinata, ; Sánchez‐Rivera, Recio, Ramos, & Gómez‐Ruiz, ).…”

“…Our previous report showed that several antihypertensive peptides are present in γ‐aminobutyric acid (GABA)‐rich fermented milk produced by Lactococcus lactis subsp. lactis biovar diacetylactis 01‐7 (Hagi et al, ). Our results suggest that unique functional peptides produced by the 01‐7 strain are found only in GABA‐rich cheese.…”

Food Metabolomics: A New Frontier in Food Analysis and its Application to Understanding Fermented Foods

“…Other similar studies on the food metabolomics studies of fermented foods that have been reported in the literature include foods from milk [58,59] soybean [27,28,65] and cereals [61,63,64] (Table 1). Others include kimchi [62], myeolchi-aekjeot [66] and saeu-jeot [67].…”