Submitted to: Protein Engineering
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/26/2001
Publication Date: N/A
Citation: Interpretive Summary: The maximal production of fermentable sugars from the starch contained in cereal seeds can only be obtained by using enzymes that are stable at the temperatures used during industrial processing of the seeds. Only one of the necessary enzymes present in barley seeds has sufficient stability to significantly contribute throughout the duration of the industrial process. The remaining three necessary enzymes only contribute during the initial stages of the process when the temperatures are cooler. We increased the stability of one of these three enzymes by changing one of its amino acids. It can contribute to the industrial process for a significantly longer period of time, thereby increasing the output of fermentable sugars.
Technical Abstract: The thermal stability of alpha-glucosidase is important because the conversion of seed starch to fermentable sugars during industrial production of ethanol (e.g. brewing, fuel ethanol production) typically takes place at temperatures of 65-73C. Unfortunately, the enzyme purified from barley is not stable at these temperatures. In this study, we investigate the thermostability of alpha-glucosidases from other organisms compare their deduced amino acid sequences and change selected amino acids in the barley alpha-glucosidase in an attempt to increase its thermostability. One mutation resulted in an enzyme with significantly enhanced thermostability. The effects of temperature and pH upon the enzymatic activity of this mutated alpha-glucosidase are documented in this manuscript and are compared to those characteristics of the original (wild type) enzyme.