Some factors affecting the stability of glucoamylase immobilized on hornblende and on other inorganic supports

Glucoamylase from four different companies was studied: three had similar stability (half‐life at 50°C about 140 hr); the fourth was less stable (half‐life at 50°C about 20 hr). The immobilized enzymes were all less stable than their soluble counterparts: immobilized enzyme stability depended on the soluble enzyme used, the support, and method of immobilization. Thus enzyme bound to Enzacryl‐TIO was less stable than enzyme bound to hornblende (metal‐link method); this, in turn, was less stable than enzyme bound to hornblende by a silane–glutaraldehyde process. Bound enzyme stability was also improved by the presence of substrate or product (starch maltose or glucose). After 110 hr at 50°C in the presence of maltose (10% (w/v)) one preparation (a more stable soluble enzyme boul1d to hornblende by a silane–glutaraldehyde process) retained over 95% of its activity: activity loss was too low to permit the estimation of a half‐life.