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

The shelf life of enzyme based analytical systems to measure ethanol a nd hydrogen peroxide has been enhanced using neutral dextrans and comb inations of cationic polymers or zinc ions and a sugar or sugar alcoho l. Dry enzyme preparations of alcohol oxidase with these stabilisers r etained 80-100% enzyme activity over periods of up to 2 months when th ermally stressed at 37-degrees-C whilst controls in the absence of sta bilisers 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 pol ymers diethylaminoethyl (DEAE)-dextran and Gafquat 755N. A combination of zinc ions and lactitol, has also been used to stabilise horseradis h peroxidase at very low enzyme concentrations. Full activity was reta ined for 10 days at 37-degrees-C in the presence of stabiliser whilst unstabilised enzyme lost 64% of the initial activity under the same co nditions. 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 etha nol kit based on alcohol oxidase.