Molecular cloning and biochemical characterization of oligo-1,6-glucosidases from Bacillus subtilis and Bacillus licheniformis

Abstract

Oligo-1,6-glucosidase (O-1,6-G, EC 3.2.1.10) is an enzyme hydrolyzing α-l,6-glucosidic linkages of isomalto-oligosaccharides isomaltooligosaccharides (IMOs). Two oligo-1,6-glucosidases from Bacillus subtilis and B. licheniformis were cloned and expressed in Pichia pastoris GS115. At the shake-flask fermentation level, the activities of these two recombinant enzymes were 1085 and 1037 U/mL. The respective optimal temperatures for BsOG and BlOG were 40 and 45 °C, and the pH optima were 7.0 and 6.5, respectively. BsOG and BlOG were stable over pH ranges of 6.5–8.0 and 6.0–7.0. These enzymes can hydrolyze isomaltulose, isomaltose, isomaltotriose, panose, sucrose, amylopectin, maltodextrin and other natural substrates and had higher affinity for isomaltose, but they exhibited weak activity toward amylose. Moreover, they converted isomaltotriose and panose in IMOs into glucose and oligosaccharides. Our results have provided a foundation for exploiting oligo-1,6-glucosidases with desired biochemical properties from various microorganisms.