Cooperative action of α-glucanotransferase and maltogenic amylase for an improved process of isomaltooligosaccharide (IMO) production

Maltogenic amylase and alpha-glucanotransferase (alpha-GTase) were employed in an effort to develop an efficient process for the production of isomaltooligosaccharides (IMOs). Bacillus stearothermophilus maltogenic amylase (BSMA) and alpha-GTase from Thermotoga maritima were overexpressed in Escherichia coli using overexpression vectors. An IMO mixture containing 58% of various IMOs was produced from liquefied corn syrup by the hydrolyzing and transglycosylation activities of BSMA alone. When BSMA and alpha-GTase were reacted simultaneously, the IMO content increased to 68% and contained relatively larger IMOs compared with the products obtained by the reaction without alpha-GTase. Time course analysis of the IMO production suggested that BSMA hydrolyzed maltopentaose and maltohexaose most favorably into maltose and maltotriose and transferred the resulting molecules simultaneously to acceptor molecules to form IMOs. alpha-GTase transferred donor sugar molecules to the hydrolysis products such as maltose and maltotriose to form maltopentaose, which was then rehydrolyzed by BSMA as a favorable substrate.