Whole mean gas hold-up epsilon(g), liquid recirculation velocity U-ld and mixing time t(m) were measured in a 0.12 m(3) airlift reactor, with an external recirculation loop (ALR-EL), which was used for the production of the exopolysaccharide, scleroglucan, by cultivation of the filamentous fungus, Scleroticum glucanicum. Under identical fermentation conditions, the effects of air flowrate and the viscosity of the culture fluid on epsilon(g), U-ld and t(m) were investigated. In the range studied, empirical correlations for epsilon(g), U-ld, and t(m) with both superficial velocity U-gr and consistency coefficient K were obtained and expressed separately.