Immobilization of amyloglucosidase using two forms of polyurethane polymer

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Abstract
Amyloglucosidase was covalently immobilized using two hydrophilic prepolymers: Hypol® FHP 2002 (creates foams) and Hypol® FHP 8190H (creates gels). The foamable prepolymer was superior as a support for enzyme immobilization. The percent activity immobilized in the polyurethane foams was 25 ± 1.5%. Large substrates (> 200,000 daltons in mol wt) were hydrolyzed as effectively as smaller ones by the immobilized enzyme. TheK m value of the foam-immobilized enzyme increased from 0.76 mg/mL (free) to 0.86 mg/mL (immobilized), whereas the Vmax dropped from 90.9 (free) to 12.4 nmol glucose/min/ mL (immobilized). The long-term (2 mo) storage stability of amyloglucosidase was enhanced by immobilization in foams (70% activity retained; free enzyme only retained 50%). Immobilization also improved the enzyme stability to various denaturing agents (sodium chloride, urea, and ethanol). The immobilized enzyme exhibited increased stability compared to the free enzyme at high temperatures (95°C). Both glycogen and starch could be utilized by the immobilized enzyme, indicating that this technique could prove useful for starch hydrolysis.