Synthesis of photo-crosslinkable hydrogel membranes for entrapment of lactase enzyme

Polyvinyl alcohol (PVA) cinnamate ester derivative (PVCN) was prepared by partial esterification of PVA using cinnamoyl chloride with various extents and then was examined using different instrumental and spectral techniques that confirm the chemical structure of the photo-active product. The obtained PVCN derivatives were casted in membranes that were able to cross-link when exposed to a strong UV light via 27 pi + 27 pi cycloaddition reaction, which was traced by UV-vis light spectra. The textures of the obtained membranes were then observed by SEM after freeze-drying to evaluate the effect of esterification degree on the cross-linking density. The PVCN membranes were also utilized as carrier support to immobilize the lactase enzyme by entrapment method and the immobilized lactase kept around 76% of its activity and presented remarkable thermal stability and resistance toward the environmental pH disturbances compared to the soluble lactase. Moreover, the kinetic parameters obtained from the kinetic experiments demonstrated an observed decrease in the vmax values from 40.35 to 27.62 U mg-(1) along with an increase in the Km values from 0.203 to 0.432 mM upon the lactase entrapment, which implies a depressed affinity between the lactase and its substrate. However, after 8 reuse cycles, the entrapped lactase still maintained around 85% of its activity revealing promising economic feasibility of the utilized entrapment technique.