| The acid urease could resolve urea and prevent the formation of urethane, which is a kind of cancerogenic substance. The bacterial strain which can produce acid urease was fermented. In the seven litres fermentor, the bacteria increased rapidly in the first sixteen hours, after 24 hours, the maximum activities reach 1.75U/mL. In the twenty-five litre fermenter, the bacteria increased rapidly in the first sixteen hours too, after 22 hours, the maximum activities reach 2.23U/mL.Comparison of cell disruption:a small amount of enzyme extracted in the laboratory appropriateness of using ultrasonic crushing, enzymes in the large-scale preparation, the choice for high-pressure cell disruption breaking better.Immobilization of acid urease optimum alginate concentration, calcium chloride concentration and chitosan concentration was 2.0 g/100mL,5.0 g/100mL and 0.3g/100mL respectively, the optimal immobilization time was 2.5 hours. The appropriate concentration of glutaraldehyde was 0.1%, the crosslinking time was 3h, and the rate of enzyme immobilization was 82.3%.Immobilized acid urease wine optimum temperature is 40℃, the optimum pH is 4.0, half-life is 74 days, the immobilized acid urease in wine between 25-55℃has better thermal stability of enzymes, the relative enzyme activity is more than 80%, the pH stability range of 3-6.5, and free acid urease optimum temperature is 35℃, the optimum pH is 5.5, half-life is 28 days.Immobilized acid urease can reuse 13 times, the total removal of urea reaches 60%.Because of the penetration and steric effect, the influence of friction bits of metal ions and organic acid immobilized enzyme effect less than free acid urease.The concentration of alcohol has little effect on the enzyme activity.The effect of remove urea in rice wine during continuous use of immobilized acid urease, as shown below:the 150g immobilized acid urease make 34.2mg/L decreased to 13.6mg/L of the urea concentration in four litre rice wine,the removal of urea was 60%. The flavor of rice wine has not changed basically in the content and little change in content of several substances.the content of ethylcarbamate was decreased.According to the amount of 0.05U/mL acid urease add to the rice wine with crude enzyme urease powder, liquid enzymes and the cell acid urease powder respectively; the cell acid urease powder was still undissolved completely after 72 hours, the effect of removal of urea less than liquid enzyme and enzyme powder. The removal of urea respectively was 63% and 59% the liquid enzyme and enzyme powder. Added the acid urease 0.05U/mL,0.08U/mL and 0.12U/mL to rice wine respectively to the 8L new rice wine which was not fried in the rice wine production, in the first day of rice wine with high enzyme adding, the urea content is slightly low, the third day, different enzyme concentration of urea removal or less. Fried rice wine on the 85℃, after half an hour, the formation of ethylcarbamate was significantly lower in rice wine which urea was removed in the previous experiments.
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