Effect of Glycosylation on the Physicochemical Properties, Structure and Iron Bioavailability of Ferritin Extracted from Tegillarca granosa

Iron deficiency anemia (IDA) is a major global health problem. Tegillarca granosa has been considered as an excellent source of iron given its high content of iron-binding protein, ferritin. The aim of the present study was to determine the physicochemical properties, protein structures, and iron uptake of ferritin extracted from T. granosa, and to evaluate the potential impacts of chitosan glycosylation on these characteristics. Based on Box-Behnken design and response surface methodology, the optimal conditions for glycosylation included a ferritin/chitosan mass ratio of 4:1, a pH of 5.5, a reaction time of 10 min, and a reaction temperature of 50 degree celsius. Glycosylation caused decreased surface hydrophobicity and elevated water-holding capacity of ferritin due to the introduction of hydrophilic groups. Additionally, glycosylation improved antioxidant capacity of ferritin by 20.69%-189.66%, likely owing to the protons donated by saccharide moiety to terminate free radical chain reaction. The in vitro digestibility of ferritin was elevated by 22.56%-104.85% after glycosylation, which could be associated with less beta-sheet content in secondary structure that made the glycosylated protein less resistant to enzymatic digestion. The results of the iron bioavailability in Caco-2 cells revealed that ferritin (78.85-231.77ng mg(-1)) exhibited better iron bioavailability than FeSO4 (51.48-114.37 ng mg(-1)) and the values were further elevated by glycosylation with chitosan (296.23-358.20 ng mg(-1)), which may be related to the physicochemical properties of ferritin via glycosylation modification. These results provide a basis for the development of T. granosa derived ferritin and its glycosylated products, and can promote the utilization of aquatic resources.