This work studies the influence of two substances - a polymer and a surfactant - upon the gas-liquid hydrodynamics in a bubble column contactor to analyse the effect of a surfactant in a viscous liquid to simulate biosurfactant production. These kinds of substances can have an important influence upon the gas-liquid hydrodynamics, primarily upon the bubble size which has a direct relation to the gas-liquid interfacial area used to transfer the oxygen from the gas-to-liquid phase. The present study analyses the influence of these substances, individually and combined, upon the hydrodynamic parameters (gas hold-up, bubble diameter and interfacial area) to reach conclusions on the joint effect and the possible synergic behaviours. Specifically the surfactant presence shows positive effect upon interfacial area though a viscous liquid phase is used. (C) 2012 Elsevier Ltd. All rights reserved.