Activity of enzymes immobilized on plasma treated polyester

The aim of this study was to investigate the effect of 3 different surface plasma treatments on the immobilization of β-galactosidase on a fibrous PET nonwoven membrane. Two methods 1. Entrapment in a thin calcium alginate coating and 2. Direct sorption, were used to immobilize the enzyme. The three different plasma treatments for surface activation of PET nonwovens were: 1. Air atmospheric DBD plasma, 2. Cold remote plasma-CRP with 100% N₂ and 3.- CRP with a mixture of N₂/O₂ gases. Plasma treatment of the PET fiber surface increased the quantity of immobilized enzyme using the entrapment method, and the degree of alginate film cross-linking highly influenced the enzyme activity. Highest enzyme activity was reached for the PET treated with air atmospheric plasma and cross-linked with 0.25 g/l of CaCl₂. With the direct sorption method, greater amounts of enzyme were immobilized as compared to the entrapment method, but a considerable proportion of enzyme lost their catalytic activity. Only with the CRP N₂/O₂ plasma treatment, up to 90% of sorbed enzyme maintained their activity. Reusability study showed that for the optimized entrapment method, a progressive decrease in activity was observed after each use cycle. With the optimized sorption method using N₂/O₂ CRP plasma, no decrease in enzyme activity was detected, and the immobilized enzyme could be used over more than 15 cycles.