The Impact of Thermostable α-Glucosidase on the Production of Fermentable Sugars During Mashing

摘要

α-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℃. After exposures as short as 10 min to these temperatures, α-glucosidase has less than 5% of the activity it had at 30℃. We hypothesized that a more thermostable α-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 α-glucosidase (control) or recombinant α-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 α-glucosidase. Hence, we conclude that the presence of a thermostable α-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.