Synthesis of Yeast High F Value Oligopeptide by Ultrasonic Filtration and Multienzyme Hydrolysis

An integrated process was developed to prepare high F valued yeast oligopeptides according to the characteristics of raw materials,which could be controlled step by step and amplified. Using active dry yeast as the initial material,the most suitable enzyme was selected from several common endonucleases after ultrasonic crushing of homogenate. The crude peptides were concentrated by nanofiltration and a small amount of free amino acids were removed. The α-chymotrypsin and carboxypeptidase A were used to hydrolyze the yeast crude peptides into oligopeptides with smaller molecular weight and a large amount of aromatic amino acids were dissociated. The free aromatic amino acids could finally be removed by selective adsorption to obtain high F value oligopeptides. It was found that alkaline protease was the most suitable enzyme to extract yeast protein. The optimum conditions of yeast cell extraction were as follows:The ratio of material to liquid was 1:6,the temperature was 50℃,the amount of enzyme added to 1 g active dry yeast was 1000 U·g^-1,pH was 8.0 and the time of enzymatic hydrolysis was 6 h. The operation condition of nanofiltration was that 500 Da nanofiltration membrane was used to concentrate 3 times at 0.3 MPa.Single factor experiments were carried out on α-chymotrypsin and carboxypeptidase A and the optimum conditions for enzymatic hydrolysis of α-chymotrypsin were obtained:The amount of enzyme added to 1 g yeast crude peptide 6000 U·g^-1,temperature 40℃,pH8.0,hydrolysis time 4 h. The optimum conditions of enzymatic hydrolysis of carboxypeptidase A were as follows:The amount of enzyme was 4 U·mL^-1,the temperature was 40℃,pH was 7.5 and the time was 4 h. Activated carbon adsorption dearomatization conditions:Adsorption time 2 h,adsorption temperature 30℃,adsorption pH2.5 and adsorption carbon liquid ratio 1:10. Several batches of high F valued yeast oligopeptides with F value between 30 and 40 had been obtained successfully under this integrated process. It was proved that this integration process could produce high F valued yeast oligopeptides efficiently and stably,which had certain guiding significance for industrial production of high F value yeast oligopeptides.