Bioactive peptides are short amino acid sequences that lie dormant within the parent proteins of everyday foods. They do nothing while locked inside the protein chain, but once the protein is broken down by digestive enzymes, laboratory hydrolysis, or microbial fermentation, these fragments are released and can exert measurable physiological effects, from scavenging free radicals to lowering blood pressure and modulating the immune system. Whey, the liquid left over from cheese production, is a particularly attractive source because it makes up 15 to 20 percent of milk protein and is packed with essential amino acids such as leucine and cysteine, the latter serving as a building block of the antioxidant glutathione.

There is a catch, however. Whey proteins are highly hydrophobic and notoriously resistant to enzymatic hydrolysis, meaning that conventional commercial enzymes often fail to cut them at the right places to liberate their embedded bioactive sequences. The research team at Dankook University, led by Cheolhyun Kim, turned to an alternative strategy: fermentation with lactic acid bacteria strains that carry their own powerful proteolytic enzyme systems. Because these bacteria evolved to digest milk proteins as a nitrogen source, their enzyme cocktails can slice whey proteins in ways that commercial enzymes cannot, generating novel peptides at low production cost.

The researchers isolated ten bacterial strains from homemade dongchimi samples collected across South Korea. Using 16S rRNA gene sequencing, they identified eight strains of Leuconostoc mesenteroides, one strain of Pediococcus pentosaceus, and one strain of Latilactobacillus sakei, which they designated DC10. Dongchimi-derived strains were deliberately chosen because kimchi bacteria used in dairy fermentation can sometimes impart undesirable flavors, so the team pre-screened for strains with both probiotic potential and technological compatibility with dairy products. All ten isolates proved Gram-positive and survived artificial gastric juice at pH values between 1.5 and 3.0 as well as 24 hours of exposure to 0.3 percent oxgall bile, a robustness profile considered essential for probiotic applications.

When the strains were tested for proteolytic activity on skim milk agar, L. sakei DC10 stood out, producing a clear digestion zone wider than 23 millimeters, the largest among all ten isolates. The team then inoculated DC10, along with two L. mesenteroides strains, into a 10 percent whey protein concentrate solution and fermented it at 37 degrees Celsius for 20 hours. Using the TNBS colorimetric method to track free amino groups, they observed that the degree of hydrolysis climbed rapidly during the first four hours and plateaued after about 16 hours, confirming that the bacteria were actively cleaving peptide bonds throughout the fermentation.

Sodium dodecyl sulfate polyacrylamide gel electrophoresis provided a visual confirmation of the protein breakdown. Bands corresponding to the major whey components, including lactoferrin, bovine serum albumin, immunoglobulins, beta-lactoglobulin, and alpha-lactalbumin, appeared between 14 and 100 kilodaltons in the unfermented sample. After 16 hours of fermentation with DC10, the higher molecular weight proteins had largely disappeared, degraded into smaller fragments. The fermented solution was then passed through a preparative gel filtration column to separate the resulting peptides into distinct fractions by molecular weight.

Fraction 3 emerged as the star of the study. In calcium solubilization assays, it achieved roughly 85 percent calcium solubility, below the 93.67 percent of casein phosphopeptides, the industry-standard calcium carrier, but well above unhydrolyzed whey protein. Because casein phosphopeptides are relatively expensive, the researchers argue that whey-derived calcium-binding peptides could serve as a cost-effective alternative for calcium-fortified foods and nutraceuticals. Peptides typically chelate calcium through electron pairs on their amino and carboxyl groups, with side chains of leucine, aspartic acid, and glutamic acid stabilizing the complex, and amino acid profiling of Fraction 3 revealed high levels of branched-chain amino acids, which previous work links to enhanced calcium absorption and vitamin D receptor expression.

The antioxidant results were equally striking. In the ABTS radical scavenging assay, most fractions outperformed non-fermented whey protein, with Fraction 3 posting the highest value. Fractions 2 and 3 matched casein phosphopeptides in DPPH radical scavenging, and Fraction 3 actually exceeded the commercial standard in the FRAP iron-reduction assay, which measures the capacity to donate electrons and break free radical chain reactions. Mass spectrometry of Fraction 3 identified four fully sequenced peptides with molecular masses between 658 and 905 daltons, including TVQVTSTAV and SLVYPFPGPIHNSLPQ, sequences previously reported in the literature as antioxidative, antimicrobial, and immunomodulatory.

To probe anti-inflammatory activity, the team treated RAW 264.7 mouse macrophage cells with the peptide fractions and then provoked inflammation with lipopolysaccharide. MTT assays confirmed that all fractions preserved more than 80 percent cell viability, ruling out cytotoxicity as a confounding factor. The fractions inhibited nitric oxide production in a concentration-dependent manner, and enzyme-linked immunosorbent assays showed significant suppression of the pro-inflammatory cytokines IL-1 alpha, IL-6, and TNF-alpha compared with LPS-stimulated controls. Because TNF-alpha drives the activation of other inflammatory mediators, damping its expression may cascade into a broader reduction of the inflammatory response.

The authors caution that their findings rest on in vitro experiments, and they call for future studies to clarify the underlying molecular mechanisms, assess bioavailability in living organisms, and explore clinical applications. Even so, the work illustrates an elegant convergence of traditional food heritage and modern protein chemistry: bacteria from a centuries-old Korean radish ferment, selected for dairy compatibility, unlocking health-promoting fragments from a cheese-industry byproduct. If subsequent animal and human studies bear out the calcium, antioxidant, and immune benefits observed in the laboratory, dongchimi-derived fermentation could offer the food industry a low-cost route to multifunctional whey ingredients that simultaneously support bone health, oxidative balance, and immune regulation.

Subject of Research: Bioactive peptide production from whey protein fermented with lactic acid bacteria isolated from Korean dongchimi

Article Title: Functional characteristics of peptides from whey proteins fermented with lactic acid bacteria isolated from Dongchimi

Article References: Yoo, J., Lee, S., Song, S., & Kim, C. (2026). Functional characteristics of peptides from whey proteins fermented with lactic acid bacteria isolated from Dongchimi. Food Science of Animal Resources, 46(1), Article 50. https://doi.org/10.1007/s44463-025-00053-6

Image Credits: AI Generated

DOI: 10.1007/s44463-025-00053-6

Keywords: bioactive peptides, whey protein, lactic acid bacteria, dongchimi, fermentation, antioxidant activity, anti-inflammatory, calcium solubilization, Latilactobacillus sakei, functional foods, probiotics, food science