Studies On The Preparation And Metal-binding Mechanism Of Antarctic Krill Peptides

Recently, using marine organisms as raw materials develop functional foods hasgain more attention. Antarctic krill (E. superba) is recognized as a target forcommercial fishing and a novel food material. It has a large biomass and is composedof high quality protein based on its amino acid composition and bioavailability. Onthe other hand, mineral deficiency is very common in many countries, which ininduced by insufficient intake and low bioavailability. Research shows that metalbinding peptides can improve the solubility and stability of metal ions, so as toincrease the absorption rate. The present study focused on preparing peptides fromAntarctic krill (E. superba) employing enzymatic hydrolysis with trypsin, neutral andalkaline proteases, and determining their affinities to metal ions (Zn2+, Ca2+, and Fe2+)and their interaction mechanisms.(1) This study confirmed that defatted Antarctic krill had the potential to be usedas a starting material for the production of bioactive peptides with metal (Ca2+, Zn2+,Fe2+) binding activities. The krill peptides contained little ash, large protein and lessthan15ppm fluorine contents. Krill peptides by different proteases exhibited distinctmetal binding activities and those by trypsin showed the best affinity towards metalions, which related to the high acidic amino acid content and molecular weightdistribution.(2) Using protein content and calcium binding activity of hydrolysates asevaluation index, the optimum enzymatic hydrolysis preparation of krill peptides wasstudies using response surface methodology (RSM). The results showed that when thehydrolysis time was3h, solid-liquid ratio of11.3:1, enzyme was3%, the enzymeworks best. Under this condition, using10g krill enzyme powder, the total amount of3.96g protein can be obtained, soluble calcium/protein is8.86mmol/g. Validation experiments show that the response surface of methodology is useful for guidingoptimum enzymatic hydrolysis preparation of krill peptides.(3) The self-assemble property of krill peptides, a flexible secondary structureand alterable three-dimensional conformation, contributed to their metal-bindingactivities. The metal complex capacity of krill peptides by trypsin increased in theorder Ca2+＜Fe2+＜Zn2+, while the complex specificity of krill peptides increased inthe order Ca2+＜Zn2+＜Fe2+. The differing binding activities of krill peptides weredue to the specific interactions (Fe2+-peptide and Zn2+-peptide) and non-specificinteractions (Ca2+-peptide) between metal ions and krill peptides.