This article focuses on the role of interfaces on lysozyme inactivation and aggregation process in stirred reactor. The first order inactivation constant of this process has found to be proportional not only to the power imparted by the impeller but also to the area of glass-liquid, air-liquid and PTFE-liquid interfaces in three reactors. Bath area and type of interfaces act on inactivation: PTFE and air are four more efficient than glass to promote lysozyme inactivation because of their hydrophobicity. As well as physical interfaces, molecular surfaces of inactivated enzymes -more hydrophobic than native enzymes- enhance lysozyme inactivation and aggregation. This enhancement has been found to be correlated with the properties of aggregates of inactivated enzymes, especially their number. Then, under mechanical stirring, inactivation-aggregation process is induced by physical interfaces and self-catalyzed by increasing hydrophobic surfaces of inactivated enzymes.