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Development and Characterization of Branching Enzymes for Improving Industrial Starches

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Title: Development and Characterization of Branching Enzymes for Improving Industrial Starches
Author: White, Jessica Kristyn Victoria
Department: Department of Molecular and Cellular Biology
Program: Molecular and Cellular Biology
Advisor: Tetlow, Ian J.
Abstract: Starch is a plant-based polyglucan made of branched amylopectin and linear amylose, and is used in many food and non-food applications. The linear component forms undesirable gels during industrial processing at temperatures below 100 degree Celsius. This thesis describes the development and characterization of branching enzymes with potential to minimize gelling by branching starch. Site-directed mutants of Deinococcus radiodurans glycogen branching enzyme (DrGBE) were made (Gln205His, Ala310Gln, Ala310Gly, Ala312Thr). Relative to wild-type, Ala312Thr exhibited increased activity with amylopectin and increased substrate-affinity for amylose and amylopectin, whereas the other mutants exhibited decreased activity with amylose and amylopectin, and Gln205His and Ala310Gln exhibited increased substrate-affinity for amylopectin. An attempt to study DrGBE activity with amylose and amylopectin within starch was unsuccessful, because changes in amylopectin masked changes in amylose. Unsuccessful attempts were made to improve activities of chimeric enzymes previously made with Zea mays and Thermus thermophilus branching enzyme domains by modifying protein expression/purification/refolding.
Date: 2018-04
Rights: Attribution-NonCommercial-NoDerivs 2.5 Canada
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Attribution-NonCommercial-NoDerivs 2.5 Canada Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivs 2.5 Canada