One-pot synthesis of cycloamyloses from sucrose by dual enzyme treatment: combined reaction of amylosucrase and 4-α-glucanotransferase.

Amylose-like α-(1,4)-glucan known as the most favorable substrate for the enzymatic production of cycloamyloses (CAs) using 4-α-glucanotransferase has a solubility issue, which requires an additional solubilization process. In our study, two glucosyltransferases, Synechocystis 4-α-glucanotransferase and Neisseria amylosucrase, were adopted to develop an efficient biocatalytic production process of CAs directly from sucrose. From one-pot synthesis, the maximum CA yield (9.6%, w/w) with 0.3 M sucrose was achieved with 10 units/mL of amylosucrase and 0.1 unit/mL of 4-α-glucanotransferase at 40 °C for a 3 h reaction in a simultaneous dual enzyme reaction mode. The size of linear α-(1,4)-glucan was positively related to the CA productivity by 4-α-glucanotransferase in a hyperbolic manner. Using our innovative bioprocess, there was no practical limitation on the initial sucrose concentration and no use of insoluble linear α-(1,4)-glucan substrate. Consequently, the concomitant dual enzyme reaction converted sucrose directly to CAs via in situ transient linear α-(1,4)-glucan as an soluble intermediate.