In order to analyze the influence of the contact mechanism in the bioleaching process, bacterial attachment on the Printed Circuit Boards (PCB) surface was avoided using a partition system. The partition system was obtained with a semi-permeable membrane of 12-14 kDa MWCO. A PCB sample of 500-1000 mu m particle size was placed inside a partition system for 144 h to compare the copper (Cu) extraction rate by Acidithiobacillus ferrooxidans, with the Cu extraction of a system without partition. The results demonstrated that when the contact mechanism was avoided, there was a decrease of 25% in the Cu extraction. When the contact bioleaching was enabled, 1.46 g of Cu was extracted from the initial 1.61 g of Cu (similar to 91% extraction). When the partition system was used, only 1.10 g of Cu was extracted (similar to 68% extraction). Bacterial adhesion experiments proved that within the first hour of the experiment, 4.30 x 10(7) cells were attached per gram of PCB, supporting that bacterial adhesion was responsible for the higher Cu extraction rate. The results for bacterial adhesion tests were consistent with Derjaguin-Landau-Verwey-Overbeek theory. (C) 2015 Elsevier B.V. All rights reserved.