The Study Of Antibacterial Peptides From Milk Protein

In this study, we detect the bioactive effect of antibacterial peptides in milk. We chose trypsin and pepsin, established the method to produce the antibacterial peptides hydrolisated from milk protein. We seperated the hydrolysate by gel filtration chromatography and ion exchange chromatography, acquired two antibacterial peptides, then studied the antibacterial activity and thermal stability of these two antibacterial peptides.The study established the method to produce the antibacterial peptides from milk protein by trypsin and pepsin on the basis of the good hydrolyzing degree and the best effect of antibacterial activity. The optimum conditions of two kinds of enzymes hydrolyze milk protein were determined by orthogonal design test and antibacterial activity experiment. The research showed that the best condition of trypsin hydrolyze milk protein was: concentration of milk protein 10%, [E]/[S] 2.5%, temperature 50°C, pH 8.0 and reaction time 3h. The best condition of pepsin hydrolyze milk protein was: concentration of milk protein 10%, [E]/[S] 14%, temperature 37°C, pH 1.5 and reaction time 3h. The study seperated the hydrolysates by Sephadex G-75 and Sephadex G-15 gel filtrate chromatography first, then chose SP-Sepharose Fast Flow to purify the collected antibacterial activity fractions. In conclusion, two antibacterial activity fractions were achieved.In order to detect the antibacterial activity of two antibacterial fractions, the study mensurate Minimal Inhibitory Concentration of two antibacterial activity fractions against S.aureus (ATCC25923), E.coli (ATCC25922), Streptococcus, Bacilli subtilis, Pasteuralla and Salmonella by Micro-dilution. The results indicated that two antibacterial fractions both have antibacterial activity against these Gram postive and negative bacterias. And the antibacteria peptides from milk protein have broad-spectrum antibacterial activity.The experiment of thermal stability of these two antibacterial peptides indicated that the antibacterial peptides from milk protein were heat-resistant.