Stabilization and optimization of purified diamine oxidase by immobilization onto activated PVC membrane

ABSTRACT The covalent immobilization of enzymes is required for most biocatalytic processes as it can broaden their applicability in various workflows. Diamine oxidase (DAO) has found important utility in food and allied industries for protection of food freshness and safety. In this study, an activated PVC strip was developed, covalently immobilized to purified DAO from pea seedlings. A comparative investigation was done on the parameters affecting catalytic activity of the free and immobilized enzyme, such as pH, temperature, and enzyme concentration. The immobilization preserved 81% of the initial enzyme activity against the substrate, putrescine dihydrochloride. The optimal pH levels of free and immobilized DAO were 7.0 and 6.5, respectively. The highest activity of the immobilized DAO was observed at 40°C while 34°C for the free enzyme. Moreover, the immobilized DAO retained about 52% of its initial activity after 10 repetitive uses and the activity was maintained after 30 days at 4°C. Therefore, this strategy may provide an excellent support for enzyme immobilization having better catalytic ability and operational stability than its free counterpart. Eventually, the results observed can be used further for various applications such as in food industry, to evaluate the freshness of real samples, and in biotechnological field to fabricate specific biosensors to detect biogenic amines content for evaluating food hygienic quality. Thus, the prepared enzyme catalyst presents a new approach for successful industrial applications.