The proof-of-concept for enzymatic electrosynthesis with simultaneous energy production has been demonstrated by using the regioselective conversion of D-sorbitol to D-fructose by D-sorbitol dehydrogenase as a model reaction. The bioreactor was composed of two electrodes, a carbon felt bioanode modified by multi-walled carbon nanotubes (MWCNT) containing D-sorbitol dehydrogenase immobilized in a silica matrix and an oxygen gas-flow cathode. The electrochemical regeneration of the NAD(+) cofactor at the bioanode was achieved by using a poly(methylene green) mediator electrodeposited on the carbon felt/MWCNT electrode. The conversion rate was 1.18 mg day(-1) cm(-3) and an energy power output up to 14.6 mu W cm(-3) at 0.1 V was reached. (C) 2016 Elsevier Ltd. All rights reserved.