Pullulanase immobilization on natural and synthetic polymers

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Abstract
This work describes the immobilization of pullulanase onto two different polymers; agarose activated with epichlorohydrin and trichlorotriazine and casein activated with epichlorohydrin, in addition to a synthetic copolymer, butylacrylate–acrylic acid (BuA/AAc). Immobilization by covalent binding yields stable enzyme activity. The operational stability of the free and immobilized enzymes showed that the enzyme immobilized by a crosslinking technique using glutaric dialdehyde (GA) showed poor durability and the relative activity decreased sharply due to leakage after repeated washing, while the enzymes immobilized by covalent bonds resulted in a slight decrease in most cases in the relative activity (around 20%) after being used 10 times. Storage for 4–6 months showed that the free enzyme lost most of its activity, while the immobilized enzyme showed the opposite behavior. Subjecting the immobilized enzymes to doses of γ‐radiation (0.5–10 Mrad) resulted in complete loss in the activity of the free enzyme at a dose of 5 Mrad, while the immobilized enzymes showed relatively high resistance to γ‐radiation up to a dose of 5 Mrad. Nuclear Magnetic Resonance (1H NMR) and FTIR measurements were carried out to confirm the structure of the polymer as well as the immobilization process of the enzyme onto the polymeric carrier. The unique biochemical characteristics, mode of action and utility of the environmentally compatible pullulanase in starch conversion are well known. Using pullulanase with β‐amylase in starch saccharification processes can increase maltose yield by 20–25%.© 2001 Society of Chemical Industry