Penicillium janthinellum strain isolated from leaf litters of oak trees from montane alpine forests of Shivalik hills (India) produced high levels of beta-glucosidase both during solid-state fermentation (796 units/gds) and shake flask cultures (65.3 units/ml). The peptide mass fingerprinting of the secretome showed a variety of glycosyl hydrolases. beta-Glucosidase was purified and characterized to be a GH3 family member that had a molecular weight (M (r)) of 101 kDa and pI of 4.5. beta-Glucosidase was optimally active at 60 A degrees C at pH 5.0 but showed appreciable activity and thermostability under alkaline conditions (pH 9.0) also. beta-Glucosidase activity was positively modulated in the presence of Mn2+ ions. The enzyme preferentially catalyzed the hydrolysis of p-nitrophenol-beta-d-glucopyranoside (pNPG) but also recognized cellobiose as substrates. K (m) and V (max) for the hydrolysis of pNPG by beta-glucosidase were calculated as 3.3 mM and 444 mu mol min(-1) mg protein(-1). Purified beta-glucosidase showed transglycosylation activity in the presence of methanol as an acceptor molecule.