Glucose Metabolism in a Microbial Fuel Cell. Stoichiometry of Product Formation in a Thionine-mediated Proteus vulgaris Fuel Cell and its Relation to Coulombic Yields

Abstract

The pattern of glucose metabolism was studied in a thionine-mediated Proteus culgaris fuel cell by using lT-labelled glucose. Added glucose was rapidly taken up by the bacteria and converted to CO', acetate, lactate and a fourth product, tentatively identified as propionate. When the glucose-dependent electric current from the fuel cells had been completely discharged, about 50% of glucose carbon was found in C 0 2 , 30% in acetate, 10% incorporated in the bacteria, and the residual 10% distributed as small amounts in various soluble products. Thus, although there was transient accumulation of lactate and 'propionate', these were largely reutilized. Coulombic yield from glucose oxidation was about 50% and correlated with the amount of CO, produced. Glucose metabolism in the fuel cell was intermediate between conventional aerobic and anaerobic conditions. Under anaerobic (conventional) conditions acetate, lactate and 'propionate' were produced and not reutilized. Under aerobic conditions, acetate and lactate were only transiently produced and the rate of glucose uptake was lower. The major limitation on coulombic yield from glucose oxidation was the production of acetate.

Electricity Generation in Microbial Fuel Cells Using Neutral Red as an Electronophore

“…Previous investigations (2,20) have shown that in microbial fuel cells in which thionin is the electron mediator, the levels of both current and potential decrease when the resting cells are depleted of glucose (i.e., fuel). We performed fuel cell experiments with NR to determine the maximal electrical productivities and stabilities that could be generated by E. coli resting cells in the presence of different glucose concentrations.…”

“…In previous studies (2,5,7,16,20) of microbial fuel cells the workers did not examine the impact of NADH oxidation via generation of electricity on cellular physiology (i.e., the impact on growth and end product formation). In resting cell studies it was assumed that generation of electricity as a consequence of NADH oxidation would result in lower levels of reduced metabolic products and higher levels of oxidized products.…”

“…Previous investigators (2,5,7,16,20) have reported that metabolic reducing power produced by Proteus vulgaris or Escherichia coli can be converted to electricity by using electron mediators, such as thionin or 2-hydroxy-1,4-naphthoquinone (HNQ) Tanaka et al (17,18) reported that light energy can be converted to electricity by Anabaena variabilis when HNQ is used as the electron mediator. Park et al (13) confirmed that viologen dyes (10,11) cross-linked with carbon polymers and absorbed on Desulfovibro desulfuricans cytoplasmic membranes can mediate electron transfer from bacterial cells to electrodes or from electrodes to bacterial cells.…”

Modelling microbial fuel cells with suspended cells and added electron transfer mediator

“…This modelling study is based on the detailed experimental observations by Bennetto's group in the 1980s [5,21,24] and Kim's work in the late 1990s [11]. For convenience, their experimental setup is briefly described here.…”

“…In this model we describe in detail only the dynamic behaviour of the anodic compartment, having in mind that a description of the cathodic chamber can follow the same approach. The model will be used to interpret experimental data obtained by Bennetto's group on MFCs with added soluble mediator (thionine) and suspended Proteus cells [5,21,24]. Such a model is also useful because it points to parameters that still need to be measured.…”