A novel ethanol biosensor based on the bulk incorporation of alcohol dehydrogenase (ADH) into a colloidal gold (Au-coll)-multiwalled carbon nanotubes (MWCNTs) composite electrode using Teflon as binding material is reported. The composite Au-coll-MWCNTs-Teflon electrode exhibited significantly improved electrooxidation of NADH when compared with other carbon composite electrodes, including those based on carbon nanotubes. Amperometric measurements for NADH at +0.3 V showed significant differences in sensitivity between Au-coll-MWCNTs-Teflon and MWCNTs-Teflon composite electrodes. Incorporation of ADH into the bulk electrode material allowed the construction of a mediatorless ethanol biosensor. Both the enzyme loading and the NAD(+) concentration in solution were optimized. The ADH-Au-coll-MWCNTs-Teflon biosensor allowed a limit of detection for ethanol of 4.7 mu mol l(-1), which is remarkably better than those reported for other CNTs-based ADH biosensors. The apparent Michaelis-Menten constant was 4.95 mmol l(-1), which is much lower than that reported by immobilization of ADH onto a gold electrode. Both repeatability of the ethanol amperometric measurements, reproducibility with different biosensors, lifetime and storage ability can be, in general, advantageously compared with other ADH-CNTs biosensors. The biosensor was applied for the rapid determination of ethanol in commercial and certified beer samples. (C) 2007 Elsevier Ltd. All rights reserved.