Identification and characterization of bioactive peptides produced by selected strains of lactic acid bacteria

Bioaktivni peptidi podrijetlom iz kazeina i proteina sirutke najbrojnija su skupina bioaktivnih tvari prisutnih u mliječnim proizvodima. To su proteinski fragmenti koji nastaju tijekom probave u humanom organizmu ili tijekom procesa prerade mlijeka metabolizamskom aktivnošću prisutnih bakterija mliječne kiseline. Cilj ovog rada bio je izolacija, pročišćavanje i razdjeljivanje bioaktivnih peptida iz uzoraka svježih sušenih sireva i sirutki kromatografijom ionske izmjene, tekućinskom kromatografijom isključivanja po veličini i spektrometrijom masa na MALDI-TOF/TOF uređaju. Ispitano je antimikrobno i antioksidativno djelovanje izoliranih bioaktivnih peptida. Također, provedena je neciljana analiza i identifikacija proteina iz uzoraka sira i sirutke u svrhu karakterizacije peptida s bioaktivnim djelovanjem. Rezultati provedenih metoda ne pokazuju antimikrobno i antioksidativno djelovanje izoliranih bioaktivnih peptida. Međutim, neciljanom analizom proteina identificirani su bioaktivni peptidi čije aminokiselinske sekvence odgovaraju bioaktivnim peptidima iz baze podataka, a za koje je ranije utvrđeno i u literaturi opisano: ACE-inhibitorno, imunomodulatorno, antitrombotično, antioksidativno i antimikrobno djelovanje.Bioactive peptides originated from casein and whey proteins are the most numerous group of bioactive substances present in dairy products. They are protein fragments that are synetised in the food digestion process in human body or during milk processing by the metabolic activity of the lactic acid bacteria. The aim of this study was to isolate, purify, and separate bioactive peptides from samples of fresh dried cheeses and whey by ion-exchange chromatography, size-exclusion chromatography, and MALDI-TOF/TOF mass spectrometry. The antimicrobial and antioxidant activities of isolated bioactive peptides were tested. Also, non-targeted analysis and identification of proteins from cheese and whey were performed to characterize peptides with bioactive activity. The results of the implemented methods do not show the antimicrobial and antioxidant activity of isolated bioactive peptides. However, non-targeted protein analysis identified bioactive peptides whose amino acid sequences correspond to bioactive peptides from the database. As previously identified, their activities were described in the literature as ACE-inhibitory, immunomodulatory, antithrombotic, antioxidant, and antimicrobial activity