Starch hydrolysis by a co-immobilized alpha-amylase and glucoamylase
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Series/Report no.:Food, Agricultural, and Biological Engineering. Graduate student poster competition, 2009
The industrial hydrolysis of starch involves several steps and several enzymes including, alpha-amylase (AA), glucoamylase (GluA), and pullulanase. Among the enzymes only GluA is used in immobilized form. There are several studies investigating immobilization of starch hydrolysis enzymes individually, however, only few studies exist on immobilization of multi-enzyme system. The objective of this study is to develop a co-immobilized enzyme system for single step hydrolysis of starch to glucose. The immobilized enzyme system comprised of entrapped GluA inside the calcium alginate beads and adsorbed AA on the surface of the beads. The arrangement will provide the hydrolysis of starch into oligosaccharides on the surface followed by saccharification into glucose by glucoamylase entrapped inside the beads. Co-immobilized enzyme system was prepared by dripping a mixture of alginate and glucoamylase into CaCl2 solution followed by bringing the GluA containing beads into contact with alpha-amylase solution for adsorption. Starch hydrolysis reaction was performed at 55oC using 5mg/ml starch solution at pH 5.5. Glucose and starch concentrations in the reaction medium were monitored during reaction. The initial reaction rate was calculated from glucose concentration-time and starch concentration-time data. The immobilization efficiencies for glucoamylase entrapment and alpha amylase adsorption were determined to be 45% and 54% respectively. Development of a co-immobilized enzyme system will improve the efficiency of starch hydrolysis process by reducing the number of steps in the process therefore reducing the enzyme and processing costs.