Research On Isolation And Purification Of Antibacterial Peptides From The Small Intestine Of Duck And Application On Chilled Pork Preservation

Antibacterial peptides are the basic materials by which animal immune defense system resists microbial invasion. It has become a hot research focus at home and abroad now. To explore the biological activities and the effects that intestinal antimicrobial peptides have on chilled pork preservation, the antibacterial peptides were extracted from duck intestinal mucosa for studying their antibacterial activities caused by various physical and chemical factors. Meanwhile, antibacterial peptides were added into chilled pork in order to explore their effects on preservation. The specific content and result are as follows:1-Isolation and purification of antibacterial peptides from the small intestine of duckThe fresh small intestines of duck were firstly grinded, lixiviated from acetic acid, and then treated by ultrafiltration and Sephadex G50gel filtration chromatography. The fractions were obtained and tested for antibacterial activities. Meanwhile, Tricine SDS-PAGE was adopted to analyze the eluted products with antibacterial activities. The molecular weight of the antibacterial peptide was estimated to be about6.5ku and the concentration was about6.458mg/mL tested by Bradford method.2. Antibacterial activities of ABPs caused by various physical and chemical factorsThe detection of the antibacterial activities of antimicrobial peptides and research on the impact of temperature and pH on the activities of antimicrobial peptides have been done, the results of which showed that both the temperature and pH have effect on the activities. Their antibacterial activities have little change at40℃-60℃for30min (p>0.05), but decrease after being treated for30min at80℃and above(p<0.05), indicating that the antimicrobial peptides have heat resistance. The antibacterial activities of antibacterial peptides from duck’s intestinal mucosa have a good sensitivity in different pH. They have strongest antibacterial activities in the environment of pH7.0, while the antibacterial activities largely decline in the environment of pH<6.0and pH>8.0.3. The single effect of antibacterial peptides of the small intestine of duck on the preservation of chilled porkThrough using double dilution method to initially filter the5-10ku-concentration preservative of antibacterial peptides from the small intestine of duck, the results showed that the concentration of the preservative should be at least0.1652%,0.3125%and0.625%respectively, in order to inhibit Escherichia coli, Salmonella and Staphylococcus aureus. Based on this conclusion, by determining sensory indicators, physical and chemical indicators and microbial indicators,5-10ku antibacterial peptides from the small intestine of duck in chilled pork preservation were evaluated. The results showed that5-10ku antibacterial peptides from the small intestine of duck had certain freshness, which could inhibit the growth and reproduction of bacteria, and the effect enhanced with the increase of the concentration of5-10ku antibacterial peptides from the small intestine of duck. Its effective preservation concentration was0.8%.4. Composite preservation of duck intestine antibacterial peptides with Natamycin and NisinBased on the single factor experiment with relevant data and predecessors’researches, an orthogonal experiment design was conducted to explore the optimum proportion of preservation. The results showed that the optimal formula of combined use of the antibacterial peptides from small intestines of ducks with Nisin and Natamycin was as follows:0.9%duck intestine antibacterial peptide,0.05%Nisin and0.03%Natamycin.