A new beta-glucosidase (DtGH) representing 40% identity with an apple seed glycosidase (ASG) was cloned from Dictyoglomus thermophilum. DtGH showed extremely high thermostability in aqueous solution, with half-lives of 533, 44, and 5 h measured at 70, 80 and 90 degrees C, respectively. Therefore it was used for direct glycosylation of n-octanol at 70 degrees C instead of 50 degrees C as usually. As a result, the glucose based conversion was increased by 27%, but the time spent to reach equilibrium was decreased from 7 d to 3 d. This enzyme also exhibited excellent stability under the reaction environment, retaining 70-80% of its initial activity after 7 d of incubation at 70 degrees C in either 1.7 M glucose solution or octanol-aqueous (85:15, v/v) system. It could retain part of synthetic activity even in boiling water. Owing to the strong glucose-tolerance and extremely high thermostability, DtGH should be promising for various glucosides synthesis. Crown Copyright (c) 2012 Published by Elsevier Ltd. All rights reserved.