PRESERVATION OF SHELF-LIFE OF ENZYME-BASED ANALYTICAL SYSTEMS USING A COMBINATION OF SUGARS, SUGAR ALCOHOLS AND CATIONIC POLYMERS OF ZINC IONS

The shelf life of enzyme based analytical systems to measure ethanol and hydrogen peroxide has been enhanced using neutral dextrans and combinations of cationic polymers or zinc ions and a sugar or sugar alcohol. Dry enzyme preparations of alcohol oxidase with these stabilisers retained 80-100% enzyme activity over periods of up to 2 months when thermally stressed at 37-degrees-C whilst controls in the absence of stabilisers lost 74% of the initial activity over 7 days at 37-degrees-C. The sugar alcohol, lactitol and the cyclic polyalcohol, inositol gave the highest stabilisation effect in conjunction with the cationic polymers diethylaminoethyl (DEAE)-dextran and Gafquat 755N. A combination of zinc ions and lactitol, has also been used to stabilise horseradish peroxidase at very low enzyme concentrations. Full activity was retained for 10 days at 37-degrees-C in the presence of stabiliser whilst unstabilised enzyme lost 64% of the initial activity under the same conditions. The use of the stabiliser combinations has found application in promotion of the shelf life of diagnostic alcohol kits and neutral, unsubstituted dextrans have been tested in the production of an ethanol kit based on alcohol oxidase.