The fungus Metarhizium anisopliae is commonly cultivated on rice, and the extraction of its spores remains a critical step with room for optimization in biofactories. Rotary drums are emerging as a promising technology. This study evaluated the effect of drum rotation speed (30 and 60 rpm) and particle moisture content (0.250; 0.111; and 0.053 kg-w/kg-ds) on the collision forces and frequencies of rice particles during the extraction process. To this end, the Discrete Element Method (DEM) was applied to simulate particle motion and collisions. The simulations were carried out using a rotary drum with a diameter of 20 cm and a length of 33 cm, equipped with two straight lifters. Spherical particles with structural and material properties referring to conidiated rice particles of different moisture contents were used. The DEM input parameters, restitution as well as static and rolling friction coefficients for particle-particle and particle-wall contacts, were experimentally determined. The experiments indicated that the moisture content of the particles predominantly affects the sliding friction coefficient, while the softness resulting from the cooking of the rice mainly influences the coefficient of restitution. The rolling friction coefficient, in turn, was primarily impacted by the sphericity of the particles. Additionally, the reduction in moisture content, by decreasing the drum's filling degree, promoted the expansion of the active layer, the region associated with more intense particle collisions. The results indicated that, despite the higher collision velocities observed at 60 rpm, the frequency of impacts with sufficient energy to overcome adhesive forces did not significantly increase compared to the 30 rpm condition. As a major outcome, DEM simulations clearly revealed that the reduction of particle size, associated with decreasing moisture content, resulted in a considerable drop of the filling degree, yielding an expansion of the active layer and therefore enhanced particle mobility. This is an important finding with great interest for the scale-up of continuous spore extraction in rotary drums.