|Muslin, Elizabeth - UNIV WISCONSIN-MADISON|
|Clark, Suzanne - UNIV WISCONSIN-MADISON|
Submitted to: Brewers Digest
Publication Type: Abstract Only
Publication Acceptance Date: June 25, 2001
Publication Date: N/A
Technical Abstract: The thermal stability of alpha-glucosidase is important because the conversion of barley starch to fermentable sugars during industrial production of ethanol (e.g. brewing, fuel ethanol production) typically takes place at temperatures of 65-73 degrees Celsius. We investigated the thermostability of alpha-glucosidases from four plant species, compared their deduced amino acid sequences, and tested the contribution of proline residues to the thermostability of alpha-glucosidase. The alpha- glucosidase from barley (Hordeum vulgare) was significantly less thermostable than the other three alpha-glucosidases. A comparison of the published deduced amino acid sequences of these four alpha-glucosidases revealed conserved proline residues in the three most thermostable alpha- glucosidases that were not found in the barley enzyme. Site-directed mutagenesis was done on recombinant barley alpha-glucosidase to create proteins with prolines at these conserved positions. The thermostability (T50) of one of these mutant enzymes was 10 degrees Celsius higher than the non-mutated enzyme.