Altar Laver (porphyra Haitanensis) In The Separation, Preliminary Purification Bacteriostatic Activity Of The Peptides And Its Mechanism Of Action Research

In this article the antibacterial activity of protein hydrolysate from Porphyra haitanensis was screened and the antibacterial peptides in the protein hydrolysate were preliminarily purified, followed by the research on the antibacterial mechanism. The results indicated:The water-soluble protein hydrolysate by pepsin has the inhibitory activity to Staphyloccocus aureu, so Staphyloccocus aureu is determined to be the indicative strain. The hydrolysate was purified sequentially by ultra-filtration, Bio-Gel P-10and DEAE Sephadex A-50chromatography. The molecular weight range (42.9KD-80.7KD) of antibacterial polypeptides (named DSA-1) was detected by SDS-PAGE. Further research showed that the antagonistic effects were observed in all combinations of DSA-1+high temperature, DSA-1+long storage time, DSA-1+alkaline environment or DSA-1+VE, and the synergistic effects were observed in all combinations of DSA-1+EDTA, DSA-1+citric acid, DSA-1+Vc or DSA-1+DMSO, and ultraviolet and common metal ion (K+、Na+、Ga2+、Mg2+、Fe2+)had no effect on DSA-1’s antibacterial activity. Results of study on the growth curve and colony morphology of Staphyloccocus aureu indicated that DSA-1could restrain logarithmic split period of Staphyloccocus aureu and affect its colonial morphology. In the culture solution of Staphyloccocus aureu treated by DSA-1, alkaline phosphatase, B-galactosidase and ultraviolet absorption objects could be detected and the conductivity value was increased. The results revealed that DSA-1may damage the somatic cell wall and cytoplasmic membrane of Staphyloccocus aureu, thus cause the increasing of cytoplasmic membrane permeability and large intracellular material let out. When Staphyloccocus aureu was treated by DSA-1, somatic cell morphology became irregular, somatic cell surface became coarse, every somatic cell was scattered distribution, and most somatic cell gathered lumpy ultimately by Scanning Electron Microscope. By Transmission Electron Microscope, when Staphyloccocus aureu was treated with DSA-1, somatic cell wall and cytoplasmic membrane were damaged, cytoplasm disintegrated and pyknosis, intracellular cavity became large, and somatic cell became broken ultimately. By SDS-PAGE, the result showed that some protein bands disappeared from somatic cell all protein bands, and some protein bands became dim, when Staphyloccocus aureu was treated by DSA-1. So it can be inferred that the antibacterial mechanism of DSA-1to Staphyloccocus aureu is as follows:DSA-1can damage somatic cell wall and cytoplasmic membrane, increase permeability of cytoplasmic membrane, and thus cause large intracellular material let out. At the same time, DSA-1may enter into somatic cell, restrain some protein synthesis, or cause some protein’s degradation.