HYDROLYSIS OF SUCROSE BY IMMOBILIZED Saccharomyces cerevisiae INVERTASE

Abstract

Invertase from Saccharomyces cerevisiae was immobilized by entrapment in carrageenan gel beads and used for sucrose hydrolysis. The immobilization efficiency was 88% when the concentration of the added enzyme was 100 unit/ml of gel and dropped to 49% upon increasing the added enzyme concentration to 500 U/ml. The immobilized enzyme remained fully active after 12 weeks of storage at 4°C. The hydrolytic activity of the enzyme was found to be influenced by temperature and pH. The preferred hydrolysis temperature was 55 °C for both the free and immobilized forms. The optimum pH was 4.5 for the free enzyme and was 4.5 – 5.5 for the immobilized enzyme. Km values for the free and immobilized invertase were 63.4 and 87.8 mM, respectively. Vmax values for free and immobilized invertase were calculated as 31.4 and 24 mM.min-1, respectively indicating lower affinity by the immobilized enzyme for its substrate and lower reaction velocity. In a continuous process using packed bed column, hydrolysis percentages of 84, 29 and 18% were obtained by using flow rates of 0.25, 1 and 2 bv/hr, respectively. On the contrary, the specific productivity was enhanced by increasing the flow rate in the column.