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Introduction: Bioactive peptides can have various positive effects, such as the prevention of diseases or the modulation of physiological systems. For our research, we selected four peptides identified in kombucha-treated milk extracts that have been shown to have a strong antihypertensive effect, as well as two histatins (Hst5 and Hst8) that have an antimicrobial effect. Their interactions with Cu(II) metal ions were investigated using isothermal titration microcalorimetry (ITC) and UV-Vis techniques. In addition, the antimicrobial activity of these peptides against C. albicans, S.aureus and E. coli, an opportunistic human pathogens, was investigated. C. albicans causes mucosal and systemic infections in susceptible individuals and E. coli is involved in various intestinal and extra-intestinal infections. Aim: The aim of our work was to investigate the interactions of peptides with potential biological activity with Cu(II) ions and their influence on C. albicans S. aureus and E. coli growth. Material and methods: The affinity of the metal-peptide interaction and the changes in enthalpy and entropy were studied using the ITC technique. The UV-Vis technique was used to characterize the formation of Cu (II) complexes wiTheach of the peptides studied. All these experiments were performed at a pH around 6 to mimic the pH of human skin. The microbiological studies were performed using the dilution susceptibility testing method in Sabouraud Dextrose liquid medium and Mueller-Hinton medium (MH). Results: All peptides: AVPQEVLNENLLR, YLQGSNLVVPLTDD, KFKGFVEPFPAVE, FVAPEPFVFGKEK, DSHAKRHHGYKRKFHEKHHSHRGY, KFHEKHHSHRGY (named by us Pep1-Pep4, Hst5 and Hst8 respectively) bind Cu (II) ions with quite high affinity (Kd in the range of 35-92 μM). All reactions were endothermic and entropy-driven. A microbiological assay showed that Pep3 and Pep4 have an inhibitory effect on E. coli by binding Cu(II) ions. Pep4 also has inhibit influence of S. aureus growth. In addition, Hst5 and Hst8 with the addition of Cu(II) inhibit the growth of C. albicans and E. coli to a small extent. Conclusions: Peptides 3 and 4 as well as histatin 8 have potential, as they have a slightly inhibitory effect on the microorganisms C. albicans, S. aureus and E. coli. They therefore represent material for planning further research with them and their analogues designed by us in the future. [ABSTRACT FROM AUTHOR]