Bioreactive Membranes through Layer-by-Layer Assembly

Immobilizing enzymes within membrane pores is advantageous because immobilized enzymes exhibit greater stability than free enzymes, and it provides a means of directing the biocatalytic reaction. Two common methods of enzyme immobilization are through covalent bonding and electrostatic bonding. Enzymes attached electrostatically exhibit higher activities than those covalently attached because the active sites are not obstructed. The layer-by-layer (LBL) adsorption technique is a method for assembling a film of layered polyelectrolytes. An advantage of the LBL technique is that the properties of the assembled film such as its thickness and overall surface charge can be controlled. Thus, for a membrane functionalized with the LBL technique, the permeability and selectivity of the membrane can be controlled. In this study, glucose oxidase enzymes are immobilized with a layer-by-layer assembled membrane. Glucose oxidase is a dimeric protein with a molecular weight of 160 kDa and a pI of 4.2. Glucose oxidase catalyzes the reaction of b-D-glucose to hydrogen peroxide and D-glucono 1,5 lactone, which is then hydrolyzed into gluconic acid. The effects of the residence time, substrate concentration, and pH on the activity of the immobilized enzyme were considered in this study. Also, studies were conducted to prove that the enzyme could be detached from the membrane while maintaining its activity and fresh enzyme can be reattached to the same assembly.

This research was sponsored by the REU/NSF Program and NIEHS.