Acta Agrophysica, 2007, 9(1), 233-244 ENHANCEMENT OF THERMAL STABILITY OF ASPERGILLUS ORYZAE ALPHA-AMYLASE USING STABILIZING ADDITIVES

Ab s t r a c t . The thermal degradation of Aspergillus oryzae α-amylase in the presence of sugars (sucrose, trehalose) and polyols (sorbitol, glycerol) as stabilization additives was investigated. The aim of the study was to test whether it is possible to estimate the heat stability of the enzyme based on the amount of hydroxyl groups provided in a buffer solution from different sources. The thermal inactivation experiments were performed at 68°C. Every additive tested showed a protective effect on the enzyme heat stability, the effect being strongly dependent on the added compound concentration. Among all the stabilizing compounds investigated, sucrose exhibited the greatest protective effect. The decimal reduction time of α-amylase activity increased 33.9 times when 420 mg/ml of sucrose was added to the environment. When the same concentration of trehalose was used, the D-value increased 6.4 times compared to the value in the buffer system. The number of hydroxyl groups provided in the enzyme solution could not be related to the D-values for the enzyme thermal inactivation, meaning that the enzyme heat stability was not dependent on the number of hydroxyl (OH) groups. K e y wo r d s : α-amylase, inactivation, kinetics, stabilization, protective effect