关键词: 液态发酵, 荞麦, 多酚, 多肽, 抗氧化

Abstract: The composition and structure of phenolics produced during the liquid-state fermentation of buckwheat using Bacillus subtilis natto were identified by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). In addition, antioxidant peptides were isolated from the fermentation broth by ultrafiltration, alcohol fractionation, and macroporous resin column chromatography. The peptide profile was identified by UPLC-MS/MS. Eight phenolic compounds including caffeic acid, protocatechuic acid, syringic acid, chlorogenic acid, catechin, rutin, vitexin and hyperin were identified. The elution fraction rich in antioxidant peptides with protein content of 66.51% and oxygen radical absorbance capacity of 1 731.52 μmol/g was obtained by ultrafiltration, ethanol fractionation and chromatography on XAD-16 macroporous resin. Twenty seven peptides were identified from the fermentation products. Twenty three peptides longer than 7 amino acids were obtained through database search against Swissprot using Mascot, which have not been reported in the BIOPEP database. All these peptides contained hydrophobic amino acids and eleven of them contained at least one amino acid with strong antioxidant activity. The IY dipeptide fragment in GDKIYNVF, the LY dipeptide fragment in CRNLLLYPAGA, the PW dipeptide fragment in PWFFTST, and the GPP tripeptide fragment in QGSGGPPIV were reported as antioxidants according to the BIOPEP database. The identified phenolics and peptides contributed largely to the antioxidant activity of the fermentation product.

Key words: liquid-state fermentation, buckwheat, phenolics, peptides, antioxidant