A novel beta-glucosidase gene, bgl1G5, was cloned from Phialophora sp. G5 and successfully expressed in Pichia pastoris. Sequence analysis indicated that the gene consists of a 1,431-bp open reading frame encoding a protein of 476 amino acids. The deduced amino acid sequence of bgl1G5 showed a high identity of 85 % with a characterized beta-glucosidase from Humicola grisea of glycoside hydrolase family 1. Compared with other fungal counterparts, Bgl1G5 showed similar optimal activity at pH 6.0 and 50 A degrees C and was stable at pH 5.0-9.0. Moreover, Bgl1G5 exhibited good thermostability at 50 A degrees C (6 h half-life) and higher specific activity (54.9 U mg(-1)). The K (m) and V (max) values towards p-nitrophenyl beta-d-glucopyranoside (pNPG) were 0.33 mM and 103.1 mu mol min(-1) mg(-1), respectively. The substrate specificity assay showed that Bgl1G5 was highly active against pNPG, weak on p-nitrophenyl beta-d-cellobioside (pNPC) and p-nitrophenyl-beta-d-galactopyranoside (ONPG), and had no activity on cellobiose. This result indicated Bgl1G5 was a typical aryl beta-glucosidase.