Proučevanje fizikalno-kemijskih in funkcionalnih lastnosti proteinov sirotke in njihovih hidrolizatov

Gruden, Špela (avtor), Poklar Ulrih, Nataša (mentor)

Sirotka je glavni stranski proizvod v proizvodni sira in skute, katera zaradi negospodarnega ravnanja, predstavlja enega glavnih onesnaževalcev živilske industrije z vidika okolja. Hkrati pa sirotka predstavlja bogat vir proteinov kot so laktoferin (Lf), laktoperoksidaza (LPO) in beta-laktoglobulin (BLG), s številnimi strukturnimi in funkcionalnimi lastnostmi, kateri predstavljajo velik potencial za izrabo v živilski in farmacevtski industriji. V doktorski nalogi smo pokazali, da je temperaturna stabilnost Lf odvisna od stopnje saturacije z Fe3+ ioni, medtem ko slednja ne vpliva na pH stabilnost Lf. Z izvedbo encimske hidrolize Lf, pri uporabi različnih encimov in pogojev encimske reakcije, smo pridobili raznolike hidrolizate Lf s protibakterijsko in antioksidativno aktivnostjo. Prvič smo pokazali protibakterijsko aktivnost Lf in peptidov Lf proti Latilactobacillus sakei. Strukturna stabilnost in encimska aktivnost LPO je bila odvisna od pH, temperature, tipa in molarne koncentracije pufra, medtem ko je prisotnost 10 mM Ca2+, Mg2+ in Na+ vplivala le na strukturno stabilnost LPO. Delna odstranitev Fe3+ in Ca2+ iz LPO je vodila v nižjo temperaturno stabilnost ter nižjo encimsko aktivnost LPO. BLG kot del WPI, smo uporabili za tvorbo WPI gelov po metodi toplotne in hladne gelacije, s katerimi smo uspešno kapsulirali vitamin D3 in peptide Lf. WPI geli, tvorjeni pri različnih pogojih, so imeli zaradi strukturnih razlik različno stabilnost v simulirani želodčni tekočini. Pokazali smo, da BLG A pri različnih vrednostih pH, veže dve molekuli vitamina D3. Z raziskavami zajetimi v doktorski disertaciji smo pokazali številne pozitivne fizikalno-kemijske in funkcionalne lastnosti analiziranih proteinov, ki bi pozitivno prispevale k učinkoviti izrabi sirotke.

• Jezik: Slovenski jezik
• Ključne besede: sirotka, proteini sirotke, laktoferin, peptidi laktoferina, laktoperoksidaza, beta-laktoglobulin, protibakterijska aktivnost, antioksidativna aktivnost, strukturna stabilnost, encimska aktivnost, kaspulacija, vitamin D3
• Vrsta gradiva: Doktorsko delo/naloga
• Tipologija: 2.08 - Doktorska disertacija
• Organizacija: BF - Biotehniška fakulteta
• Založnik: [Š. Gruden]
• Leto izida: 2024
• PID: 20.500.12556/RUL-159218
• UDK: 637.344:577.112
• COBISS.SI-ID: 200635139
• Datum objave v RUL: 04.07.2024

GRUDEN, Špela, 2024, Proučevanje fizikalno-kemijskih in funkcionalnih lastnosti proteinov sirotke in njihovih hidrolizatov [na spletu]. Doktorska disertacija. Š. Gruden. [Dostopano 4 maj 2025]. Pridobljeno s: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=slv&id=159218

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Study of the physico-chemical and functional properties of whey proteins and their hydrolysates

Izvleček

Whey is the main by-product of cheese and casein manufalcture, which represents one of the main pollutants of the food industry from an environmental point of view, due to uneconomic management. However, whey is a rich source of proteins such as lactoferrin (Lf), lactoperoxidase (LPO) and beta-lactoglobulin (BLG), with many structural and functional properties, that represents great potential for use in the food and pharmaceutical industry. In a doctoral thesis we demonstrated that the temperature stability of Lf depends on the degree of saturation with Fe3+ ions, while the latter does not affect the pH stability of Lf. By carrying out enzymatic hydrolysis of Lf using different enzymes and enzymatic reaction conditions, we obtained diverse Lf hydrolysates with antibacterial and antioxidant activity. We demonstrated for the first time the antibacterial activity of Lf and Lf peptides against Latilactobacillus sakei. The structural and enzymatic activity of LPO depended on pH, temperature, type and molar concentration of the buffer, while the presence of 10 mM Ca2+, Mg2+ and Na+ only affected the structural stability of LPO. Partial removal of Fe3+ and Ca2+ from LPO resulted in lower temperature stability and lower enzymatic activity of LPO. BLG as part of WPI was used to form gels by the heat and cold gelation method, which successfully encapsulated vitamin D3 and Lf peptides. WPI gels formed under different conditions had different stability in simulated gastric fluid due to structural differences. In addition, we demonstrated that BLG A binds two vitamin D3 molecules at all different pH values that affect its quaternary structure. With the research covered in the doctoral thesis, we demonstrated many positive physico-chemical and functional properties of the analyzed proteins, that will have positive contribution to the efficient use of whey.

• Ključne besede: whey, whey proteins, lactoferrin, lactoferrin derived peptides, lactoperoxidase, beta-lactoglobulin, antibacterial activity, antioxidant activity, conformation stability, enzymatic activity, encapsulation, vitamin D3