A rotating-drum reactor with a gas-sparger of microfiltration ceramic membrane was used for arsenopyrite bioleaching by Acidithiobacillus ferrooxidans. The gas mass transport performance could be improved by adjusting the aeration rate and drum rotation speed, and high bioactivity of bacterial strains could be maintained at high pulp densities. Arsenopyrite bioleaching showed that higher pulp density could be allowed in the rotating-drum reactor, which was favorable to the reactor used in the bioleaching of sulfide minerals. (C) 2012 Elsevier Ltd. All rights reserved.