Synthesis of isomaltooligosaccharides using 4-O-α-d-isomaltooligosaccharylmaltooligosaccharide 1,4-α-isomaltooligosaccharohydrolase.

Isomaltooligosaccharides (IMOs), including isomaltose, are valuable oligosaccharides, and the development of methods to synthesize high-purity IMOs has long been underway. We recently discovered a novel enzyme, 4-O-α-d-isomaltooligosaccharylmaltooligosaccharide 1,4-α-isomaltooligosaccharohydrolase (IMM-4IH), that showed promise for improving the synthesis process. In this study, we establish methods for synthesizing isomaltose and IMOs consisting of a variety of degrees of polymerization from starch using IMM-4IH. With 5% substrate, by combining IMM-4IH with 1,4-α-glucan 6-α-glucosyltransferase from Bacillus globisporus N75, the yield of isomaltose was 63.0%; incorporating isoamylase and cyclomaltodextrin glucanotransferase increased the yield to 75.3%. On the other hand, by combining IMM-4IH with 1,4-α-glucan 6-α-glucosyltransferase from Paenibacillus sp. PP710, IMOs were synthesized. The inclusion of isoamylase and α-amylase led to the 136 mM IMOs, consisting of oligosaccharides from isomaltose to isomaltodecaose, from 10% starch. The development of these efficient methods will be an important contribution to the industrial production of IMOs.