Entrapment of enzymes using organo-functionalized polysiloxane copolymers.

The present study expands previous work [(1984) Biochim. Biophys. Acta. 797, 343-347] by showing that organo-functionalized polysiloxane copolymers could entrap two of the most frequently immobilized enzymes, i.e. urease and invertase with retention of biological activity. Urease was solidly entrapped in the polymer formed from a 1:3 mixture of 3-aminopropyltriethoxysilane and tetraethylorthosilicate. The entrapment yield and the activity of the entrapped enzyme are significantly greater than with other techniques reported to date. Significantly, the entrapped enzyme possessed greater activity than its solution counterpart (36% at higher amounts of enzyme entrapped). The entrapment process also rendered the enzyme more stable toward pH and temperature, and less susceptible toward the action of urea at high concentrations. In addition, the entrapment process significantly increased the stability, both operational and storage, of the urease enzyme. When invertase was entrapped in the same copolymer, it retained two thirds of its solution activity, but the entrapment yield was lower than that of urease. Results obtained during this study also suggested that the protein may be influencing polymer development in these systems and that the resultant polymer in turn may be affecting the enzyme's activity (see following paper for further discussion).