| Oyster is the world's first marine aquaculture shellfish and one of China's important marine resources.In China,the oysters were still in the primary stage,and mainly used for fresh food,oyster resources are not fully explored,so the development and utilization of oysters with high value is of great significance.Zinc deficiency is still common in developing countries.People in some areas need additional zinc to maintain their health.Inorganic zinc has the disadvantages of stimulating the gastrointestinal tract and low absorption utilization rate,so looking for safe and high absorption utilization zinc-rich products has gradually become a research hotspot in recent years.In this study,oysters were used as raw materials to prepare oyster peptides by enzymatic hydrolysis,and zinc chelates of oyster peptides were prepared by chelation technology.Then the composition,structure and physicochemical properties of the oyster peptide zinc chelate were analyzed;its anti-proliferative activity was evaluated by the Hep G2 cell and its mechanism of action was discussed.Finally,it was applied to the zinc-rich culture of lactic acid bacteria to prepare zinc-rich lactic acid bacteria,which broadens its market application and lays the foundation for the development and utilization of zinc-rich products.The main results of this study are as follows:(1)The ultrasonic pretreatment process parameters of oyster peptides were determined as follows: ultrasonic power 640 W,peptide concentration 0.12 g / m L,temperature 50?,time 30 min.Then the response surface optimization analysis method was used to optimize the chelating process conditions: peptide / zinc ratio 15,p H6.53,time 80 min,peptide concentration 0.06 g / m L,and the zinc chelation rate of the oyster polypeptide zinc chelate was measured to be 72.13%.(2)The composition of the oyster polypeptide zinc chelate was determined as follows: moisture 7.09%,crude protein 40.74%,zinc 12.62mg/g.As far as its amino acid composition,the contents of aspartic acid,glutamic acid,glycine and proline are higher,which are significantly higher than those of other amino acids.The oyster peptide zinc chelate has good storage stability,the maximum water absorption rate after storage for 6 days is 14.96%,which is significantly lower than the water absorption rate of the oyster peptide before chelation(59.13%);The oyster peptide zinc chelate has good in vitro resistance oxidation activity,The highest free radical scavenging rate of ABTS radicals is 81.58%;and the zinc ions were released mainly in the stomach.(3)The oyster peptide zinc chelate has a significant anti-proliferative effect on Hep G2 cells.At a zinc ion concentration of 125 ?mol / L,the cell viability is 72%.Its mechanism of action may be increasing the activity of antioxidant enzymes(superoxide dismutase SOD,catalase CAT,glutathione peroxidase GSH-Px),blocking the S phase of the cell division cycle,and induce cells apoptosis(the highest rate of apoptosis is 59.2%).(4)Oyster polypeptide zinc chelate can be used as a safe source of zinc.Adding it to lactic acid bacteria for zinc-rich culture can improve product activity and zinc utilization.Lactobacillus bulgaricus is a potential dominant zinc-rich bacterium.By optimizing the zinc-rich culture conditions,the best zinc addition time is 10 hours after inoculation,and the zinc ion concentration is 50 ?g / m L.Zinc-rich culture can improve the antioxidant activity of the supernatant of lactic acid bacteria.Among them,the antioxidant activities of the supernatant of Lactobacillus bulgaricus cultured with oyster polypeptide zinc(ABTS free radical,DPPH free radical,superoxide anion free radical scavenging activities)are all higher than other zinc-rich lactic acid bacteria(Zinc-rich Lactobacillus fermentum,Zinc-rich Lactobacillus casei,zinc-rich Lactobacillus acidophilus).The gastrointestinal release rate of Lactobacillus bulgaricus cultured with oyster peptide zinc-chelates was 4.34%,and the bioavailability was the highest(29.78 %),which was significantly higher than that of zinc sulfate and zinc gluconaterich lactic acid bacteria. |
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