Proteomic analysis of goat milk kefir: Profiling the fermentation-time dependent protein digestion and identification of potential peptides with biological activity

Abstract

Kefir is a fermented dairy product, associated to health benefits because of being a probiotic and due to the presence of molecules with biological activity. In this work, we have profiled the peptide composition of goat milk kefir at three different fermentation times using a peptidomics approach, in order to study changes in peptide concentrations and patterns of protein digestion throughout the fermentation time. We identified 2328 unique peptides corresponding to 22 protein annotations, with a maximum of peptides found after 24 h fermentation. We established different digestion patterns according to the nature of the proteins, and quantified the changes in the peptides appearing in all the fermentation times. We also identified 11 peptides that matched exactly to sequences with biological activity in databases, almost all of them belonging to caseins. This is the most comprehensive proteomic analysis of goat milk kefir to date. Highlights  A comprehensive peptidomic analysis of goat milk kefir at different fermentation times.  Establishment of protein digestion patterns throughout the milk fermentation.  Quantification of occurring peptides along the fermentation process.  Identification of peptides with potential biological activity in goat milk kefir.

Antimicrobial activity of goat’s milk fermented by single strain of kefir grain microflora

“…The highest quantitative reduction of indicator microorganisms in the case of fermented whey was found in the fermented whey by Lactobacillus parakefiri. The study conducted by Izquierdo-González et al [14] indicated that 24 h fermentation of goat's milk by kefir microflora maximizes the variety of peptides with potential biological activity. Lactobacillus kefiranofaciens subsp.…”

“…There are few data describing the functional properties of bioactive compounds released during the fermentation of goat's milk with kefir grain microflora. Kefir grain microflora consisting of bacteria of the genus Lactobacillus, Lactococcus and yeast of the genus Kluvermyces and Saccharomyces connected extruded exopolysaccharide matrix-kefiran produced by Lactobacillus kefiranofaciens [14]. The aim of the study was to evaluate the antibacterial properties of biologically active compounds released during the fermentation of goat's milk by selected bacterial strains that are part of the kefir grain microflora.…”

A comprehensive review on bioactive peptides derived from milk and milk products of minor dairy species

“…Different bioactivities of kefir were reported in literature, however, identification and characterization of such peptides is limited. Izquierdo-González et al (2019) profiled the bioactive peptides in goat milk kefir after 12, 24 and 36 h of fermentation using peptidomics approach. In total, 11 bioactive peptides (Table 4) were identified after different fermentation time; however, maximum concentration was obtained after 24 h which decreased thereafter.…”

Bioactive peptides from food fermentation: A comprehensive review of their sources, bioactivities, applications, and future development

“…Although LAB assimilate the resultant peptides for growth, a large number of peptides are still remained and accumulated during fermentation. By far, the commonest BPs found in the fermented milk are the angiotensin‐converting enzyme inhibitory (ACE‐I) peptides (Chen et al., 2015; Izquierdo‐González et al., 2019; Rai et al., 2017). As shown in Table 1, the main trend reflects a general penchant for using LAB in animal's milk fermentation.…”

“…Recently, Izquierdo‐González et al. (2019) produced kefir by fermenting goat's milk for different period of time (0, 12, 24, and 36 hr) at 25 °C under aerobic condition with 5% (w/v) kefir grains. The LC–MS/MS analysis revealed that 2,004 peptides were discovered, among which 11 peptides were identified with bioactivities (antibacterial, antioxidative, dipeptidyl peptidase IV [DPP‐IV] inhibitor, ACE‐I, and antithrombotic properties) after 24 hr of fermentation.…”