The influence of substrate composition on extracellular protein production was evaluated in media containing glucose, lodgepole pine or aspen as carbon sources. Common to all media, basal salts contained, per liter, 2g NH4NO3, 2g KH2, 0.5 g MgSO4·7H2O, 0.1 g CaCl2·2H2O, 1 mg thiamine hydrochloride and 1 mL trace element solution (Teknova, T1001). Aspen and pine were added to 5 g per liter, while the glucose cultures received 2.5 g per liter. All cultures contained 100 mL media in 500 ml Erlenmeyer flasks and, following inoculation with macerated mycelium, incubated on a rotary shaker (100 RPM) at 24°C. Aspen (Populus grandidentata) and lodgepole pine (Pinus contorta) were Wiley milled and sieved to one mm mesh prior to inoculation. Triplicate cultures were harvested after 5 and 10 days.