IMPROVED ACTIVITY RETENTION OF ENZYMES DEPOSITED ON SOLID SUPPORTS

Enzymes deposited on solid support usually show good stability when operated in organic solvents. Decreased stability of the enzyme preparations was noticed when low enzyme loadings were used (e.g., with Celite as support; less than 1 mg enzyme/g). It was possible to avoid the activity loss by the addition of an additive which protects the enzyme during the immobilization. Proteins (such as albumin, gelatin, and casein) and poly(ethylene glycol) were effective additives whereas amino acids, monomeric carbohydrates, and polysaccharides had no effect. The amount of additive needed for stabilization was shown to depend on the structure of the support, more additive being required for a support with high porosity. The stabilizing effect was investigated in a series of glyceryl-controlled-pore glass (CPG) with varying specific surface areas (9.5-180 m2/g). The minimum addition of albumin, giving full stabilization, on the different supports correlated to a monolayer coverage of the surface, approximately 2-3 mg protein/m2. The effect of the additive was less pronounced when increasing amounts of enzyme were immobilized (5-40 mg enzyme/g Celite). The effect of the additives was studied using mandelonitrile lyase, but alpha-chymotrypsin and lipase P were also shown to be stabilized.