Development of a submerged culture method for high production of acid-stable α-amylase and glucoamylase using Aspergillus kawachii without glucose concentration control

Abstract

It is commonly accepted that maintaining a low glucose concentration in a culture is an important condition for high level of production of acid-stable α-amylase (ASAAase) and glucoamylase (GAase) in submerged culture using Aspergillus kawachii. Raw materials with hard husks, such as barley, are able to control the release of glucose from the raw material and maintain a low glucose concentration, thereby enabling a high production of enzymes. On the other hand, it is difficult to produce large quantities of enzymes by controlling glucose release using raw materials without hard skins. This study evaluated a culture method for high enzyme production using raw materials without hard skins, such as a sweet potato, and found that this was possible using a moderately high concentration of sweet potato. Maximum ASAAase and GAase activities were 51 units/mL and 188 units/mL, respectively, both values being sufficiently high for potential industrial use. Glucose concentration remained high over time in the culture, suggesting that other mechanisms may be mediating the increase in enzyme production, despite the impact of medium glucose concentration on enzyme production.