To prevent fouling of ultrafiltration membranes during processing of protein solutions, a high degree of turbulence should be introduced in the feed solution, keeping the energy consumption as low as possible. For this purpose, the application of fluidised beds at the upstream side of the membrane can be very attractive. In this study, the effect of fluidised particles is investigated under non-fouling and fouling conditions. In both systems, mass transfer is increased considerably by addition of fluidised particles. The main mechanism of fouling reduction is by an increased diffusion of rejected solutes from the membrane interface back to the bulk solution. Improvement of mass transfer is only a weak function of particle size and density. Therefore, the particles can be chosen as light and small as possible. This greatly reduces the energy consumption in the system and the risk of membrane damage, which may be a problem. Application of fluidised bed systems can be especially attractive in highly viscous systems in which energy consumption can be a problem.