NOVELTY - An electrochemical bioreactor system comprising a first compartment containing first electrode, second electrode, electrically conductive material connecting the electrodes, electrolyte for providing ionic conductivity between electrodes, and biocatalyst in first compartment or associated with first electrode, which comprises graphite felt and at least one electron mediator, is new.    USE - The electrochemical bioreactor system is used to produce electricity using electrical energy as a source of reducing power in fermentation or enzymatic reactions and using electron mediators and biocatalyst, such as cells or enzymes. The electrochemical bioreactor system has an improved electrode that has use as an enzymatic fuel cell, as a sensor for succinate detection, and as an engineered catalyst for the synthesis of fumarate or succinate. It can be used as either an enrichment device for electrophilic microorganisms, i.e. those which use an electrode as an electron acceptor, or electron donor for energy conservation.    ADVANTAGE - The electrochemical bioreactor system has improved electrode that enhances the rate of electron transfer from cells, that has use as an enzymatic fuel cell, that has use as a sensor for succinate detection or as engineered catalyst for the synthesis of fumarate or succinate. The electrode has an enzyme immobilization protocol to link nicotinamide adenine dinucleotide (NAD+), neutral red, and fumarate reductase to the electrode.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for :    (1) electrically recycling nicotinamide adenine dinucleotide (NADH), nicotinamide adenine dinucleotide phosphatase (NADPH), or adenosine triphosphate (ATP) during cellular metabolism and biochemicals production in an electrochemical bioreactor system comprising using neutral red with resting cells in the electrochemical bioreactor system; and    (2) producing electricity comprising using neutral red or Mn4+ with resting or growing cells in an electrochemical bioreactor system during microbial degradation.