Numerous foodstuffs have been developed for lactose intolerant individuals. However, current methods to reduce lactose require excessive enzyme and are not viable for small producers. A novel solution proposed to overcome these problems is the immobilization of lactase to standard food-contact packaging materials. The ability of these packages to convert lactose is dependent on the quantity and specific activity of the enzyme after immobilization. In this study, the material interface of polyethylene (PE) films was modified with polyethylene glycol (PEG) tethers of 1 kDa, 2 kDa, 5 kDa, and 10 kDa containing epoxy, acrylate, aldehyde, and succinimdyl ester end-group functionality. The results showed that a 5 kDa tether enabled maximum absolute activity of 0.49 x 10-2 ALU/cm2 when compared to tethers of different sizes with identical functionalization. Compared to succinimdyl, epoxide, and acrylate functionalized PEG tethers, an aldehyde end-group resulted in films with the highest absolute immobilized enzyme activity of 0.67 x 10-2 ALU/cm2. Regardless of tether size or chemistry, the activity retention of lactase was less than 15% compared to the soluble enzyme after immobilization to PEG-functionalized PE films. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013