Molecular cloning, characterization, and application of a novel thermostable α-glucosidase from the hyperthermophilic archaeon Pyrobaculum aerophilum strain IM2

A novel hyperthermostable α-glucosidase from the hyperthermophilic archaeon Pyrobaculum aerophilum str. IM2 (PAE1968) was successfully expressed in Escherichia coli and characterized. Recombinant PAE1968 was purified using Ni-NTA affinity chromatography to reveal a glycosidase with a predicted molecular weight (Mw) of 76 kDa. PAE1968 liberated glucose from the non-reducing ends of oligosaccharides. Multiple sequence alignment confirmed that the enzyme belonged to glycoside hydrolase (GH) family 31, and a kinetic study showed that the enzyme had a substrate preference for maltose (G2), indicating a Type-II α-glucosidase. The optimum operating conditions for the enzyme were 90°C and pH 6.0, while the enzyme retained at least 80% of maximal activity at pH 4.5–7.5. Transglycosylation and reversion reactions of PAE1968 were of a lower magnitude than for a commercial saccharification enzyme, indicating that this enzyme can be used for glucose production in the starch industry.