Switchgrass was milled to 3 different particle sizes i.e. 0.5-1mm, 1-2mm and 2-10mm and pretreated with 15% ammonia hydroxide compared with non-pretreated switchgrass. Shaker flask studies  were conducted using Trichoderma reesei Rut C-30 for production of cellulases for the selection of particle size. Scaleup tests were then tested using 2%, 5% and 10% switchgrass loading in a 5 liter fermenter. Corresponding mass transfer coefficient (K_La) were determined and enzyme activity were analyzed using HPLC and DNS methods