A study of enzyme and protein microencapsulation--some factors affecting the low apparent enzymic activity yields

Microencapsulation of aqueous solutions of enzymes, alpha-chymotrypsin (EC 3.4.21.1) and histidase (EC 4.3.1.3), with semipermeable polyamide membranes resulted in a loss of enzymic activity. The low yields (less than 40%) found with both enzymes were typical of others reported in the literature. The activity of broken histidase-containing microcapsules was greater than that of the microcapsules before breaking, and this was interpreted as being due to a simple diffusional restriction on the substrate and product. The maximum of the apparent pH-activity curve of alpha-chymotrypsin was found to be shifted one unit to more alkaline pH when the enzyme was encapsulated. This phenomenon was explained in terms of the hydrogen ion concentration in the microenvironment surrounding the enzyme being different from that in the bulk solution. Microencapsulation of aqueous solutions of enzymes is accomplished by in situ polymerization reactions at the interface of a water-in-oil emulsion. 125I-labelled proteins (albumin and fibrinogen) were encapsulated under similar conditions to determine the efficiency of the microencapsulation process. About one third of these proteins was lost during the overall preparation procedure and a further fraction was attached to the membranes of the microcapsules.