VIEW ARTICLE    DOI: 10.1094/ASBCJ-61-0142

The Impact of Thermostable alpha-Glucosidase on the Production of Fermentable Sugars During Mashing. Elizabeth H. Muslin, Charles B. Karpelenia, and Cynthia A. Henson (1,2), USDA-ARS Cereal Crops Research Unit, 1575 Linden Drive, Madison, WI 53706. (1) Corresponding author. Phone: 608/262-0377; Fax: 608/264-5242; E-mail: <cahenson@facstaff.wisc.edu> (2) Mention of a proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other suitable products. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. American Society of Brewing Chemists, Inc., 2003. J. Am. Soc. Brew. Chem. 61(3):142-145, 2003. Accepted March 4, 2003.

alpha-Glucosidase is one of the four carbohydrases present in malted barley that degrade starch. The thermostability of these carbohydrases is important because the industrial processes that convert starch to fermentable sugars typically take place at temperatures of 65-73°C. After exposures as short as 10 min to these temperatures, alpha-glucosidase has less than 5% of the activity it had at 30°C. We hypothesized that a more thermostable alpha-glucosidase could result in the increased production of fermentable sugars during mashing at high temperatures. To test this hypothesis, experimental mashes were supplemented with either nonmutated recombinant alpha-glucosidase (control) or recombinant alpha-glucosidase that had been mutated to have increased thermostability. The real degree of fermentation and the identity and quantity of maltodextrins produced were compared between these two mashes. The amounts of glucose, maltose, and maltotriose and the real degree of fermentation were significantly increased in the mashes containing thermostable alpha-glucosidase. Hence, we conclude that the presence of a thermostable alpha-glucosidase during mashing does increase the efficiency of the mashing process since more fermentable sugars are produced with no increase in the amount of raw materials added to the mash. Keywords: Barley, Hordeum vulgare, Maltase, Maltodextrins, Starch degradation

La alfa-Glucosidasa es una de las cuatro carbohidrasas presentes en la cebada malteada que degradan el almidón. La termoestabilidad de estas carbohidrasas es importante porque los procesos industriales que convierten el almidón a azúcares fermentables típicamente ocurren a temperaturas de 65-73°C. Después de exposiciones tan cortas como 10 minutos a estas temperaturas, la alfa-glucosidasa tiene menos del 5% de la actividad que tenía a 30°C. Aceptamos la hipótesis que una alfa-glucosidasa más termoestable podría dar lugar a una producción mayor de azúcares fermentables durante la maceración a altas temperaturas. Para probar esta hipótesis, las maceraciones experimentales fueron suplidas con alfa-glucosidasa recombinada sin mutación (control) o alfa-glucosidasa recombinada con mutación para tener mayor termoestabilidad. El grado verdadero de fermentación y la identidad y cantidad de dextrinas de malta producidas se compararon entre las dos maceraciones. Las cantidades de glucosa, maltosa, y maltotriosa y el grado verdadero de fermentación aumentaron perceptiblemente en las maceraciones que contenían la alfa-glucosidasa termoestable. Por lo tanto, concluimos que la presencia de alfa-glucosidasa termoestable durante la maceración aumenta la eficiencia del proceso de maceración puesto a que se producen más azúcares fermentables sin aumento en cantidad de materias primas agregadas al macerado. Palabras claves: Cebada, Hordeum vulgare, Maltasa, Dextrinas de malta, Degradación de almidón