Study On The Process Of Producing Compound Enzymes From Freshwater Fish Viscera

Thesis study on preparing high value-added and high biological activity of the fish compound enzyme product from freshwater fish viscera, to make full use of freshwater fish viscera resources and increase a high-quality enzyme source for bio-industry in our internal organs.The main contents include the basic components of freshwater fish offal, pretreatment on fish offal, optimization of process parameters on extracting crude enzyme using sodium citrate buffer solution, the determination on ammonium sulfate precipitation conditions, the choice of membrane and research on the technology of impurity and enrichment, and the determination on freeze-drying process parameters.The main results are as follows:1. The main components and contents of freshwater fish viscera are 12%~20% content of crude protein, 6%~10% content of the enzyme protein, 25%~35% content of fat, about 0.5% content of ash, about 25% of moisture.2. The best conditions of the extraction crude enzyme liquid, the temperature of extraction is 18℃, liquid ratio is 1:5, the pH and the concentration of sodium citrate buffer are 6.2 and 0.08mol/L, the time of extraction is 15min. The activity of total crude enzyme is 551764U, the content of enzyme protein is 5296mg.The saturation of the ammonium sulfate precipitation is 30%~70% to remove part of the hybrid protein, the enzyme activity obtained total activity is 93.82%.3. The purification and concentration are done through the ultrafiltration and nanofiltration membrane in the experiment, enzyme activity, enzyme activity recovery and purification factor of the final concentrate reach 58659.4U/mL, 63.9% and 1280.8 times. The membrane is cleaned by using compound agent and citric acid, which are sodium dodecyl sulfate and sodium polyphosphate of surfactant and EDTA of chelate complex, the water flux can return to 96% of the original flux. By using SDS-PAGE, the molecular weight distribution of target enzyme is 24.3~38.7 kD.4. The optimum conditions of freeze-drying process are 80℃of the heating temperature, 60Pa of the vacuum, 10mm of the material thickness. Freeze-drying efficiency can reach to 143.1 g×h-1×m-2 or so. After drying, the fish enzyme product is light yellow powder, enzyme activity reach to 9764.2U/g, the water content is less than 3%, with good solubility and no insoluble crystals, that the process parameters are designed rationally, the degree of drying is handled appropriately. The results show that drying nanofiltration concentrate solution by freeze-drying technique is feasible entirely.