The Antarctic Krill, Euphausia Superba) Bacteriostatic Preliminary Purification Of Active Peptide And Its Mechanism Of Action Research

Antarctic Krill is the key species of ecosystem in South Pole. It is rich not only in resoures but also in nutritional value with high protein and low lipid. Thus the high-value utilization of Antarctic Krill is of great significance.Antimicrobial activity of protein hydrolysate from Antarctic Krill, optimal enzymatic hydrolysis condition, preliminary purification using ultra-filtration, cation exchange chromatography and antimicrobial mechanism were studied in this paper. The main experimental results were as follows:l.The polypeptides from Antarctic Krill could inhibit the growth of Staphylococcus aureus.The optimum enzymatic hydrolysis conditions were as follows: the hydrolysis was carried out with neutral protease and trypsin at pH7.5and52.5℃for3hours. The enzyme dosage ratio between neutral protease and trypsin was2:5(w:w), and the total enzyme activity was3000U/g substrate.2.The polypeptides obtained were purified sequentially by ultra-filtration and cation exchange chromatography. The molecular weight range of antimicrobial polypeptide (named CMCC-1) was among254-709D detected by high performance liquid chromatography. The minimum inhibition concentration (MIC) against Staphylococcus aureus was5mg/mL.3.The antimicrobial mechanism of CMCC-1was studied with Staphylococcus aureus as indicator bacteria. The result showed that CMCC-1could inhibit cell division at logarithmic phase. Compared with control group, the results of the experimental group in which Staphylococcus aureus was treated with CMCC-1were as follows:①CMCC-1could inhibit cell division at logarithmic phase.②The protein and reducing sugar content, and the conductivity of culture medium increased, and the activity of alkaline phosphatase and β-galactosidase could be detected in the culture medium, which indicated that maybe the cell wall and membrane of Staphylococcus aureus were destroyed and thus led to the increasement of cell permeability and the leaking-out of substance inside cell.③Observation under scanning electron microscope revealed that somatic morphology became irregular and then somatic surface became coarse. The cell became much smaller, and most somatic cells gathered. The boundary among cells became dim and finally fused as a whole.④Observation under transmission electron microscope showed that the surface of Staphylococcus aureus became rough and the reproducing ability was restrained.The cell wall became thin and cytoplasm shrinked. Substance inside cell leaked out and then caused the cells death.⑤SDS-PAGE analysis result showed that some banes disappeared, and residual banes became dim.⑥The genomic DNA electrophoresis results showed that the genomic DNA bands of Staphylococcus aureus was not diffusion-like but its brightness significantly reduced.Therefore, it is supposed that CMCC-1from Antarctic Krill could destroy the cell wall and membrane, increase the cell membrane permeability and the leaking-out of intracellular substances, and thus cause the death of Staphylococcus aureu.