Preparation Of Immobilized Flavourzyme And Application In Production Of Soybean Peptide

Our country is abundant in soybean resource and now it has been the biggest country of soybean consumption in the world. Protein levels in soybean as high as 38%, of which 80% to 88% is soluble in water. The water-soluble protein is taken advantage of in processing of soybean products. Soybean protein isolation(SPI) that is rich in nutrition and no cholesterol can replace animal protein absolutely because it contains nearly twenty kinds of amino acids, especially containing the eight essential amino acids necessary for the body. The biological activity and physicochemical processing characteristics of SPI was favorable enough, which suggested that the SPI was suitable for the wide applications in industry. However, as a result of larger molecular weight, more complex molecular structure, worse solubility and indigestion after eating, SPI was further hydrolyzed into soybean peptide of small molecular weight and easier to digest, which has become a research hotspot in recent years.Chemical hydrolysis is more serious damage to the amino acids, and corrodes production equipment. Because of the mild reaction conditions and not producing toxic substances, enzymatic hydrolysis is widely applied to the production of soybean peptide. Free enzyme is unstable, easy to denaturalize and deactivate, cannot be recycled and lost in fermentation liquid, and it is difficult to separate and purify from the production, which results in lower efficient of utilization. These disadvantages limited its wide application in industrial production. In order to solve the above disadvantages and to meet the needs of industrial production, the technology of immobilization on the free enzyme can bring about good results in industrial applications. Immobilized enzyme maintains the efficient, loyal and gentle enzymatic properties of free enzyme, its stability is greatly improved, the reaction process can be controlled and facilitate continuous and automated operations, which improved the production efficiency. Above all, immobilized enzyme can be recycled reused and reduce the production cost.The preparation and properties of immobilized flavourzyme on globular cross-linked chitosan, with glutaraldehyde as crosslinking agent, were investigated. The optimal concentration of chitosan, NaOH and glutaraldehyde was 2.5%, 3% and 0.5%, respectively, and the optimal crosslinking time was 6h. The optimal flavourzyme dosage was 40mg/g carrier, and the optimal immobilizing reaction temperature, pH and time was 35℃, pH5.5 and 10 h, respectively. After immobilized, the optimal reaction temperature of flavourzyme was improved from 50℃ to 70℃, the optimal pH value was improved from 7.0 to 8.0, and the range of both temperature and pH value for keeping higher enzyme activity had been extended. The stability of storage and operation of the immobilized flavourzyme was good enough to be reused for many times, which suggested that the immobilized flavourzyme was suitable for the wide applications in industry.With the method of compound enzyme hydrolysis, produce soybean peptides from soy protein for lower production costs and higher degree of hydrolysis. Alkali protease hydrolyzed soybean protein into soluble peptide and peptone first, and after the filter residue immobilized flavourzyme was applied to hydrolyze the soluble peptide and peptone. So, substrate can diffuse into the inner of immobilized carrier to improve the rate of hydrolysis. The results showed that the degree of hydrolysis reached 17.72% when soy protein was hydrolyzed by immobilized flavourzyme at the optimum conditions: hydrolysis temperature of 65℃, pH8.0, enzyme dosage of 5%, hydrolysis time of 7h. The immobilized flavourzyme was stable enough to be reused for 7 times, and the relative activity still remained 79.1%. Therefore, there was the technical and economic feasibility to produce soybean peptides with high degree of hydrolysis using immobilized flavourzyme.