Bioelectrochemical 2-Propanol Biosensors 2-Propanol biosensors for O2-detectors based on bienzyme membranes with sequentially installed catalase and alcohol oxidase are described. Measurements were performed in undiluted media up to 20 vol.-% 2-propanol according to the principle of intermediate carrier analysis by use of a micro-dialysator, an oxygenating pump and a pressure adjusting chamber. For the extension of the measuring scale in the enzyme membrane O2 is released out of hydrogen peroxide within the phosphate buffered carrierstream by catalase. Therefore, oxygen is available to the serially installed alcohol oxidase for the enzymatic substrate transformation beyond the physically soluted part of oxygen in the measuring medium. Molecular selectivities of bienzyme membranes are described for normally used moisturizing concentrates in printeries.