Studies On Screening For Mucor Strain Of Bean Curd Milt And Producing Soybean Peptides With Multifarious Enzymes

The problem of producing flavorful polypeptides from soybean residue was discussed in this research. The routine methods such as acid, alkali and common enzymatic hydrolysate were discarded while the cooperation of self-selected protein enzyme from microbe with papain and typsin was used to produce soybean polypeptides with high degree of hydrolysis and excellent flavor.A strain of fungus that could produce protein enzyme with certain ability to decompound soybean proteins and dispel the distasteful flavor given off by the hydrolyzation of endopeptidase was selected from the traditional fermented food beancurd cheese and was named MY10. Elementary identification of MY10 showed that it belonged to mucor. The research of the relationship between growth of and enzyme production showed that the the fungus reach the maximum point when cultured in medium for 84h. The pH of medium kept dropping during the 0-48 h after cultured. At the point of 48 h, the pH was 4.2 and then pH began to ascend. After 84 h it overcame 7.0. The measurement of protease showed that the activity of enzyme derived from the fungus reached the maximum point. The rough enzyme was purified. It was first ascertained to precipitate the solution with 60%saturated (NH4)2SO4. Then the solution was made to past Sephadex G75.Through measuring enzyme activity showed that the neutral protease and alkling protease were probably existent. Enzymatic analysis showed that the optimum pH of the target enzyme system was 9.2. The optimum temperature of neutrah alkling protease were 60 ℃, 50 ℃ separately. The protein enzyme activity of the enzyme system was not very high. In order to improve the degree of hydrolysis and to get soybean polypeptides, papain and typsin were used in this research to hydrolyze soybean dregs. The soybean dregs were first hydrolyzed by single enzyme and the optimum conditions were decided. Then the optimum conditions to hydrolyzing soybean dregs by double enzymes were determined as follows: papain was first put in with the condition of55 ℃, pH 7.0, E/S=2%, concentration of substrate: 12%. After hydrolyzing for 3 h, the reaction system was quickly put into boiling water(100℃) for 15 min to denaturalize the enzyme. Then the conditions was adapted as follows: hydrolyzing temperature:50℃, pH:8.0, 1% typsin being put in. After hydrolyzing for 3 h, the reaction system was quickly put into boiling water(100℃) for 15min to denaturalize the enzyme. Under this condition, the solubility of soybean protein was 31.8% and the color of liquor was bright yellow with a heavy bitter taste. Product of rough enzyme solution from MY10 hydrolyzed by papain and typsin was used as material. The intensity of bitterness was used as guideline. Temperature, pH, time and quantity of enzyme were used as factors with 3 levels each. L9 (34) was used to arrange the experiment. It was identified that the optimum condition to wipe off the bitterness was as follows: temperature of 45 ℃, reaction time of 5 h or 6 h, pH8.0, enzyme 15 ml. Soybean polypeptides derived under this condition had no taste of bitterness but faint scent. Nutrition ingredient analysis of soybean dregs before and after enzymatic hydrolyzing showed that the concentration of amino acid after enzymatic hydrolyzing improved for 36.6647%. In addition to that, antinutrition factors such as urease, soybean agglutinin were wiped off commendably.