Thermal and pH stability
Aliquots of the immobilized and free enzyme samples were incubated at different pH values for 30 min, at 25◦C, and the remaining activity was assayed at pH 6.0, for pH stability determination. When thermal stability was assayed, aliquots of the immobilized and free enzyme were incubated at pH 6.0, at 60◦C. Periodically, samples of these suspensions or solutions were withdrawn, placed in ice baths for 30 s and the remaining activities assayed. For both studies the initial activity is regarded as 100%, and residual activity was expressed as a percentage of initial activity.