Experiments were conducted to determine the mechanisms of interaction with chromium of Aspergillus niger var tubingensis strain Ed8 in batch culture and in bioreactor experiments. Results obtained in this work showed that the interaction of A. niger var tubingensis Ed8 with Cr(VI) is based mainly in a reduction process and also, secondly, in a sorption process. Using electron microscopy techniques the ultrathin sections obtained from the mycelium biomass produced by the fungus in batch cultures showed the ability to incorporate Cr intracellulary, into low electron-dense inclusions, but not extracellularly. On the other hand, cultures without Cr(VI) of A. niger var tubingensis Ed8, grown in a bubble column bioreactor, reduced Cr(VI) immediately after repeated addition of this oxyanion; after six loads, 460 mg Cr(VI) was reduced to Cr(III) in 60 h, corresponding to a reduction rate of 2.62 mg Cr(VI) g(-1) dry biomass h(-1). (C) 2014 Elsevier Ltd. All rights reserved.