title: 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.
authors.affiliation: Animal Products Research Division, NARO Institute of Livestock and Grassland Science, Ibaraki, Japan 305-0901. Electronic address: thagi@affrc.go.jp.
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Hagi
authors.affiliation: Animal Products Research Division, NARO Institute of Livestock and Grassland Science, Ibaraki, Japan 305-0901.
authors.forename: Miho
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Animal Products Research Division, NARO Institute of Livestock and Grassland Science, Ibaraki, Japan 305-0901.
authors.forename: Masaru
authors.initials: M
authors.lastname: Nomura
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000032:analysis; D000818:Animals; D000959:Antihypertensive Agents / Q000032:analysis; D005285:Fermentation; D013294:Lactococcus lactis / Q000378:metabolism*; D055432:Metabolomics; D008892:Milk / Q000737:chemistry* / Q000378:metabolism; D010455:Peptides / Q000032:analysis; D005680:gamma-Aminobutyric Acid / Q000032:analysis / Q000096:biosynthesis*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D000959:Antihypertensive Agents; D010455:Peptides; D005680:gamma-Aminobutyric Acid
keywords: Lactococcus lactis; fermented milk; metabolome; γ-aminobutyric acid (GABA)