In the present study, the effect of carbon nanotubes (CNTs) either single walled (SWCNT) or multi walled (MWCNT) on sugar oxidation by Corynascus thermophilus cellobiose dehydrogenase (CtCDH) is investigated. The current observed for the direct electron transfer (DET) communication between the enzyme and the electrode is compared to that of the mediated electron transfer (MET) obtained from CtCDH/CNT/Os-polymer modified electrodes. The CNTs provide a high surface area for the immobilization of CtCDH and the Os-polymer and increases the amount of both on the electrode surface. The amperometric current density measured for 50 mM glucose at pH 7.4 and an applied potential of 290 mV vs. SHE in DET mode is 6.90 mu A cm(-2), which is further improved to about 8.73 mu A cm(-2) when a cross-linker is applied, whereas a 14-folds increase to 97.6 mu A cm(-2) is observed for MET when CtCDH is immobilized in the Os-polymer and cross-linked. The current densities extracted from CVs at 150 mV vs. SHE using 20 mM glucose for CtCDH immobilized with the Os-polymer, MWCNT/Os-polymer and SWCNT/Os-polymer are 139.7, 180.3 and 328.2 mu A cm(-2), respectively so a remarkable increase is observed when using SWCNT for electrode modification. The bioanode also exhibits a good stability and it retains more than 50% of its activity in multicycle CV scan after five days. Thus the bioanode based on SWCNT/CtCDH/Os-polymer/cross-linker could be a promising electrode for application as anode in enzymatic biofuel cells. (C) 2018 Elsevier Ltd. All rights reserved.