Preparation Of Manila Clam Ruditapes Philippinarum Lectin And Its Application For Fresh Keeping Fish

Bivalve mollusks the same as other invertebrate lack antibody-based immunity and rely exclusively on their innate immune responses to recognize, resist and eliminate pathogens. Their lectins are one of significant humoral immune molecules, which have a variety of biological activities. This study took Manila clam Ruditapes philippinarum as research material, isolated Manila clam lectin and researched its antibacterial activity and effect on fish preservation, which would provide theoretical basis for the development and utilization of MCL.The crude lectin was obtained by salting out used ammonium sulfate solution. For purification of the lectin used DE52 ion exchange chromatography and Sephadex G100 gel chromatograph or DEAE-Sepharose CL-6B ion exchange chromatography and Sephacryl S-200 HR gel chromatograph. The best preparation process was: first the crude liquid was mixed with a 80% saturated ammonium sulfate to get the crude lectin and then added to DEAE-Sepharose CL-6B ion exchange chromatography and Sephacryl S-200 HR gel chromatograph to get purified MCL.Antibacterial activities of MCL were studied. The results showed that MCL inhibited the growth of Shewanella sp., which was dependent on temperature. Shewanella sp. treated with MCL was observed with scanning electron microscopy. The results showed that the cell surface was wrinkled and formed more irregular holes at 30℃ than at 4℃. In the presence of MCL, the changes of Ca2+ of Shewanella sp. were analyzed. Shewanella sp. treated with MCL showed lower intracellular calcium concentration than the control. This could be because MCL disturbed the ordered arrangement of membrane lipid and changed permeability of plasma membrane, with irregular holes appearing in the plasmalemma and Ca2+ of the cells leaking out.The effects of MCL coating on quality and shelf of Pseudosciaena crocea, Trichiurus haumela, and Scophthalmus maximus during cold storage were investigated. The results indicated that the total viable count, pH, TVB-N, TMA-N and TBA of the treated fish samples were lower than the control mostly, which showed that MCL had antisepsis to Pseudosciaena crocea, Trichiurus haumela, and Scophthalmus maximus during cold storage.