Bioelectrochemical systems BESs

Pant, D., Singh, A., Van Bogaert, G., Gallego, YA., Diels, L, and Vanbroekhoven, K. (2011) An introduction to the life cyde assessment (LCA) of bioelectrochemical systems (BES) for sustainable energy and product generation relevance and key... 

The development of microbial bioelectrochemical systems (BES) has recently achieved an impressive progress [33]. The elegance of microbial bioelectrochemical systems is based on the possibility to directly link the metabolic activity of living microorganisms with electrodes - for a direct conversion of chemical into electric energy... 

The combination of the advantages of biological components (e.g., reaction specificities or selfreplication) and electrochemical processes to bioelectrochemical systems offers the opportunity to develop efficient and sustainable processes. In bioelectrochemical systems (BES), at least one electrode reaction is catalyzed by living microorganisms or isolated compounds. 

A bioelectrochemical system (BES) is an electrochemical device used to convert electrical energy into chemical energy and vice versa. A BES consists of an anode and a cathode compartment, often separated by an ion-selective membrane. The anode is the site of the oxidation reaction which liberates electrons to the electrode and protons to the electrolyte the cathode is the site of the reduction reaction, which consumes the electrons to reduce a final electron acceptor. To maintain electroneutrality of the system, protons (or other cations) need to migrate to the cathode through the ion-selective membrane. Depending on the half-cell potentials of the electrodes, a BES can be operated either as a microbial fuel cell (MFC), in which electric energy is generated, or as a microbial... 

The goal of this chapter is to present the present concepts and the present status in the field of electroenzymatic redox reactions for the synthesis of complex organic compounds. The large field of analytical applications of bioelectrochemical systems for example in biosensors will not be covered. However, it should be pointed out that analytical studies and applications present very useful information in the search for synthetic developments. 

Experimental approaches to bioelectrochemical systems include other techniques which introduce new environments for interfacial bioelectrochemical function. Introduction of single-crystal, atomically planar electrode surfaces has opened a basis for the use of the scanning probe microscopies, STM and AFM, also for biological macromolecules. Importantly this extends to the electrochemical STM mode where electrochemical surfaces, adsorbate molecules, and now also biological macromolecules can be mapped directly in their natural aqueous environment, with full electrochemical potential control in situ STM and... 

Development of bioelectrochemical systems permitting various inexpensive substances of organic nature to be used as fuel. 

Collectively, MFCs and the newer biologically catalyzed electrochemical cells have come to be known as bioelectrochemical systems (BBSs) [48-52]. As BES research becomes more sophisticated, it appears that BBSs can provide new insights into the fundamental mechanisms of electron transfer between microorganisms and... 

Logan BE. Scaling up microbial fuel cells and other bioelectrochemical systems. Appl Microbiol Biotechnol 2010 85 1665-1671. 

The successful application of microbial fuel cells (MFCs) and bioelectrochemical systems (BBSs) requires an understanding, and ultimately the optimization, of microbial activities associated with the bioelectrocatalytic conversion of chemical and electrical inputs. Researchers must always consider that MFC/BES reactors utilize living microorganisms to drive catalytic activity, and these microbes will respond to system changes in different ways than abiotic catalysts. 

Microsensors and CV can be coupled to assess ORR in cathodic biofilms operating in aerobic environments and to investigate cathodic reaction mechanisms operating in biocathodes in SMFCs and other bioelectrochemical systems. 

The main focus of this article is on the electrochemical removal of nitrogen and phosphorus from source-separated urine. Bioelectrochemical systems for urine treatment will not be discussed, because the research is still at an early stage. Some possible applications of bioelectrochemical systems for urine treatment have been presented in Udert et al. [3]. 

Electrode materials and scalable reactors - in different bioelectrochemical systems expensive electrode materials such as carbon nanotubes or precious metal electrodes are used. These materials are unconsolidated for large-scale MES. In terms of maximizing productivity and minimizing costs, cheap and reusable three-dimensional electrodes are needed. In a technical electrochemical reactor, the use of an expensive separator such as a membrane should be avoided. During the lab stage, the scalability of the reactor concept should receive attention as important parameter. 

Two other specific areas must be mentioned in this introduction the emerging fields of microbial fuel cells and microfluidic fuel cells. In some ways these two new fields can be considered embodiments of low-temperature fuel cells operating at the extreme size scales - microbial fuel cells have their genesis in the exploration of wastewater treatment in electrochemical and bioelectrochemical systems. These proposed applications are by their nature enormous in size, with reactor volumes measured in the tens of cubic meters (many orders of magnitude larger than the conventional low-temperature fuel cells). 

Schroder, U. and Harnisch, F. (2010) Electrochemical losses defining BES performance, in Bioelectrochemical Systems From Extracellular Electron Tranter to Biotechnological Application (eds K. Rabaey, L. Angenent, U. Schroder, and J. Keller), IWA Publishing, London. 

New supramolecular compounds mimicking biological cofactors have been proposed which have high redox potentials and, further, can be Hnked covalently onto supports in biotransformation systems [52]. Bioelectrochemical methods available for regeneration of nicotinamide- and flavin-dependent systems are comprehensively reviewed by Kohhnan et al. [53]. 

Enzyme-linked electrochemical techniques can be carried out in two basic ways. The first approach is to use a hydrodynamic technique, such as flow injection analysis (FIAEC) or liquid chromatography (LCEC), with the enzyme reaction being either off-line or on-line in a reactor prior to the amperometric detector. In the second approach, the enzyme is immobilized at the electrode. Hydrodynamic techniques provide a convenient and efficient method for transporting and mixing the substrate and enzyme, subsequent transport of the substrate to the electrode, and rapid sample turnaround. The kinetics of the enzyme system can also be readily studied using hydrodynamic techniques. Immobilizing the enzyme at the electrode provides a simple system that is amenable to in vivo analysis. Alternatively, the transport of enzyme product from the enzyme active site to the electrode surface is greatly enhanced when the enzyme is very near the electrode. Enzyme electrodes are an extremely important area of bioelectrochemical analysis, and many reviews are available in the literature. ... 

As noted above hpid bilayer films supported on electrodes represent an interesting bioelectrochemical interface where the potentials are of the same order as those of physiological systems, and can be readily modulated. Nevertheless, this area remains less studied except in the case of enzyme complexes such CcO where the hydrophobic environment of the lipids is necessary to maintain the integrity ofthe enzyme when immobilizing it on electrodes [304, 314]. Studies of the interaction of drugs with hpid membranes are important from many points of view, particularly considering the fact that nearly 50% of drug molecules have mem-... 

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