Stabilization of analytical enzymes using a novel polymer–carbohydrate system and the production of a stabilized, single reagent for alcohol analysis
A number of analytical enzymes including galactose oxidase, malate dehydrogenase and alcohol oxidase (from the methylotrophic yeast, Hansenula polymorpha) have been stabilized in a dry form by use of a novel, patented polymer–carbohydrate system. The enzymes were dried under vaccum at ambient temperature in the presence of a positively charged (cationic), soluble polymer such as diethylaminoethyl (DEAE)-dextran, and a carbohydrate sugar alcohol, lactitol. The dried enzymes retained high activity under conditions of thermal stress at 37 °C. Long term stability testing of alcohol oxidase indicated that 100% of the enzyme activity was retained for up to 2 months incubation at 37 °C in the presence of the stabilizers. In comparison, unstabilized enzyme, which was dried in phosphate buffer alone, retained only 26% activity after 7 d of incubation at 37 °C. Stabilized alcohol oxidase preparations have been used to produce an alcohol assay reagent kit, having a shelf life of over 2 years when stored at 4 °C. Activity loss during the drying step was also reduced in the presence of the stabilizers. This type of stabilization system has application in the long term storage of active enzymes, enzyme products and in the area of enzyme-based analytical reagents and biosensors.