Study On Activity And Sequence Structure Of Antioxidant Peptides In Lactobacillus Fermented Milk

Oxidative stress was a negative effect produced by free radicals in the body and was considered to be an important factor leading to aging and disease.Antioxidant peptides as natural antioxidants have been a research hotspot in the food field.Natural milk is an important source of high-quality protein and lactic acid bacteria have a complete proteolytic enzyme system.Therefore,so lactic acid bacteria can be used to ferment large-molecule proteins to produce small-molecule active peptides and amino acids in milk.It can increase the absorption rate of milk protein and increase the biological activity of fermented milk.In this study,fermented milk was prepared by using five common lactic acid bacteria-Lactobacillus bulgaricus,Streptococcus thermophiles,Lactobacillus plantarum.Lactobacillus paracase,Lactobacillus rhamnosu,either alone or in combination.Peptides in fermented milk were extracted and analyzed for their antioxidant activity.High-resolution mass spectrometry was used to analyze the structure of these peptides.The study found that the antioxidant activity of the peptides in the composite strain fermented milk was higher than that of the peptides produced by a single strain.Among them,the peptides extracted from the mixed fermented milk using the five lactic acid bacteria had the highest total antioxidant capacity.In antioxidant experimentin vitro,the DPPH radical and ABTS radical scavenging rates of these peptides were as high as 51.30±0.69%and 90.70±0.52%,respectively.Their metal ion reduction and chelating abilities were 496.5?mol/LTE and 94.22%and oxidation inhibition rate of linoleic acid oxidation system is as high as 85.84%.Caco-2 cells were used to evaluate the antioxidant capacity of the peptides produced in the compound strain fermented milk.The results showed that the peptide extracts could have anti-oxidation effect under the stimulation of H2O2 and reduce the damage of oxidative stress on cells,which was mainly achieved by reducing the intracellular ROS level.The peptides extracted from the mixed fermented milk using the five lactic acid bacteria have the highest antioxidant capacity in the cell,and its antioxidant capacity is equivalent to that of BHA and Trolox.In this study,the peptide sequence structure in the compound strain fermented milk was analyzed by LC-MS/MS.A total of 1601 peptides were identified in the eight fermented milk,of which 279 were shared by the eight compound strain fermented milk.The structure of the 42 peptides was the same as that reported in the literature.Quantitative analysis by LC-MS/MS showed that the contents of 42 polypeptide chains were different in different fermented milks,it was the highest levels of peptides in the compound fermented milk using L.bulgaricus,S.thermophilus,L.plantarum,L.rhamnosus and L.paracasei,and their antioxidant capacity was also the strongest.