Feasibility Study On Antiacterial Protein From Endophyte Strain In Oxya Chinensis As A Preservative

Currently, the natural micro-organisms antimicrobial preservatives which is produced with microbial metabolites as raw material by extraction, enzymatic conversion and fermentation such as technologies, which is meet the safe and efficient development trends of the food, and which is an important direction and focus of the preservation market. The bacterial strain of SDLH has been isolated from the foregut of Oxya chinensis through experiments, and has been finally identified to as the Serratia marcescens of Enterobacteriaceae, Serratia Bizio by the 16s rDNA analysis. The leavened substance has a strong antibacterial activity to Staphylococcus aureus. This thesis aims to isolate and purify the substance that has the antibacterial activities and get the antibacterial proteins, and have a rearch on its physical and chemical properties and toxicity, and its feasibility analysis used in food preservatives, which is to lay the foundation for the further development and application.The PEG 6000 method is used to extract the crude antibacterial proteins, and the purification of the proteins is by the DEAE-32 chromatography and Sephadex G-50 chromatography, then used the inhibition zone method to determinate the antibacterial activity, Bradford to determinate the contents of the proteins, and SDS-PAGE to determinate the purity. Finally the electrophoresis pure inhibitory protein that the molecular weight of about 17.0 KD is obtained.The physical and chemical properties of the inhibitory protein are preliminary studied, Temperature and pH affect the stability of inhibitory protein, Determination of the antibacterial spectrum and the minimum inhibitory concentration and the contents of Amino Acids of the inhibitory protein.The MTT method is used to detect the Cytotoxicity of the SDLH antimicrobial proteins. The toxicity of the Inhibitory protein was determined to the rat hepatocytes and human liver cancer cells, the conclusion drawns when the concentration of the SDLH inhibitory protein up to 200μg/ml, the rat hepatocytes and human liver cancer cell are cultured after 48h, the average cell survival rates were respectively 58.1% and 65.3%, indicating SDLH inhibitory protein has no significant cytotoxicity.The corrosion experiments of the SDLH inhibitory protein instead of chemical preservatives such as potassium sorbate were studied in the low-temperature minced pork. By counted the total number of bacteria and evaluated the quality of the minced pork during low temperature storage, the result show that the SDLH inhibitory protein is better than the potassium sorbate in the preservativing, indicating that the SDLH inhibitory protein which could be partiy instead of potassium sorbate can be used in preservative in meat products.