Comparison And Functional Analysis Of Small Molecular Protein Peptides In Breast Milk And Milk

Breast milk has always been considered as an ideal food, and whey protein is one of the most important ingredients in breast milk. It could be digested into active peptides in the gastrointestinal tract of the human body. The special nature of breast milk meets the need of the baby’s growth. Therefore, we should be more in-depth understanding of the composition of breast milk, to make the dairy more close to the level of breast milk. Studying on small molecule protein peptides provided a useful exploration for the development of functional food and medicinal value of nutrient factors, and could increase the utilization rate of milk. It made dairy more close to the level of breast milk, and provided a theoretical basis for the study of breast milk products.This test used breast milk and milk as raw material and The effect of gradient pressure, time, temperature and pH on ultrafiltration was investigated by using membrane flux as index, and optimized the preparation process of small molecule peptides; Small molecular peptides were isolated and purified by ultrafiltration; Study on the stability,anti-digestion, antioxidation and antibacterial activity of small molecule protein peptides; Small molecule peptides from breast milk and milk were isolated and identified by ultrafiltration technology, Tricine-SDS-PAGE and mass spectrometry. The main results were as follows:(1) The optimal separation conditions of small molecular peptides from milk were: operating temperature of 25℃, pressure of 0.25MPa, time of 30min, pH value of 7. The membrane flux could reach 14.24 L/m2·h. Through the comparative analysis, 1KDa ultra filtration method is the best purification method. The purification of small molecular protein peptides content was 1.32±0.06mg/mL. The small molecular protein peptide content was 2.37+0.11 mg/mL.(2) Amino acids of small molecular protein peptides in breast milk and milk were 14. The content of hydrophobic amino acid in milk was high, and the mass percentage was 24.26%; The essential amino acid content of breast milk protein peptide high, and the mass percentage was 21.08%.Two small molecular peptides have better heat and pH stability, and have better anti-digestion through the simulation of the human gastrointestinal tract environment analysis.(3) Small molecular peptides in breast milk (lOmg/mL) for reducing power, hydroxyl radical, superoxide radical and DPPH· scavenging rate were 69.00%,67.91%,47.86%and 60.28%, and respectively was VC 0.85,0.82,0.76 and 0.72 times, showing a strong antioxidant capacity; In contrast, small molecular peptides in milk (10mg/mL) for reducing power, hydroxyl radical, superoxide radical and DPPH· scavenging rate were 55.00%, 56.32%,38.95%and 51.63%, and were less than breast milk.Antibacterial effect of small molecule protein peptides by Oxford cup method measures were as follows:small molecule peptides in breast milk on Escherichia coli and Staphylococcus aureus had better inhibition effect. At the concentration of 10mg/mL, the inhibition zone diameter were 15.02±0.13mm and 14.29±0.46mm respectively; The antimicrobial effect of small molecule peptides in milk on two kinds of pathogenic bacteria was poor. At the concentration of lOmg/mL, the diameter of inhibition zone were 9.42± 0.19mm and 10.34±0.45mm respectively.(4) In this study, ultrafiltration and Tricine-SDS-PAGE were used to separate the small molecular protein peptides from breast milk and milk, and mass spectrometry was used for identifying. The results were as follows:It showed that there were 28 kinds of proteins in breast milk,24 kinds of proteins in milk, and 18 kinds of the same expression proteins. Breast milk contains 10 kinds of different protein peptides, for example Glutathione S-transferase P、DRB1 transplantation antigen、 Haptoglobin、Metallothionein. Milk contains 6 kinds of different protein peptides, for example Secretoglobin family 3A member 1、 Secretoglobin family 1D member 2、 CSN1S1.It also found that the function of breast milk small molecular protein peptides in the process of biological process was higher than milk’s, especially in immune system, through the functional analysis of Gene Ontology (GO); In the molecular function, the two main functions of small molecular protein peptides were the combination, and the function of breast milk small molecular protein peptides was more stronger. The milk’s involved in the molecule function of transport activity was greater than that of breast milk; In the cell, both were involved in the composition of the cell and cell membrane.Through Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, it showed that breast milk small molecular protein peptides involved in tyrosine metabolic pathway and antigen processing and presentation pathway, and milk small molecule protein peptides involved in Systemic lupus erythematosus pathway.