Mini-hydrocyclones were used to effect differential separation of a leached slurry of sulphidic ore from a continuous bioleaching process. Separations of the sulphidic ore, other non-biological solids as well as free and attached bacteria were studied. The volumetric flow split was found to be a power law function of the ratio of the spigot to vortex finder diameters. The mass recovery was shown to be a function of the outlet diameters individually, when treating a feed of the same size distribution. The recovery of bacterial activity was directly related to the mass recovery, except at high solids concentrations in the underflow stream. Following passage through a two-stage circuit of mini-hydrocyclones, it was shown that a significant upgrading of the solids concentration could be attained, enhancing downstream processing such as cyanidation. In addition, the preferential upgrading of one stream with respect to bacterial activity (measured in terms of oxygen utilisation rate) was demonstrated. This holds potential in the recycling of bacteria to the continuous bioleaching tanks to retain a higher biomass concentration and improve process robustness. By recycle of a low volume stream with reduced solids concentration, plant capacity may be improved.