CANDIDA-RUGOSA LIPASE STABILITY DURING ACYLGLYCEROL SYNTHESIS

For the enzymatic synthesis of esters, enzyme stability in alcohol-water mixtures is of great importance. When the activity of an enzyme is monitored with time in such a solution, often two inactivation regions can be distinguished. This paper presents a model to describe both inactivation regions for Candida rugosa lipase. The inactivation can be described with a two-step model, assuming the native enzyme reversibly alters its conformation to a form having a lower activity. The reversibility is experimentally verified. Both forms do inactivate at the same irreversible rate to a completely inactive form. Inactivation rates are related to the glycerol concentration. During inactivation, aggregate formation occurs. The activity of immobilized enzyme is reduced to the same level of activity as is found for free lipase. Based on the inactivation model, the initial activity of an esterifying system is calculated. It is shown that the esterification rate approximates the hydrolysis rate.