Microbial-enzymatic-hybrid biological fuel cell with optimized growth conditions for Shewanella oneidensis DSP-10.

In this work we present a biological fuel cell fabricated by combining a Shewanella oneidensis microbial anode and a laccase-modified air-breathing cathode. This concept is devised as an extension to traditional biochemical methods by incorporating diverse biological catalysts with the aim of powering small devices. In preparing the biological fuel cell anode, novel hierarchical-structured architectures and biofilm configurations were investigated.

Facile fabrication of scalable, hierarchically structured polymer/carbon architectures for bioelectrodes.

This research introduces a method for fabrication of conductive electrode materials with hierarchical structure from porous polymer/carbon composite materials. We describe the fabrication of (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) scaffolds doped with carbon materials that provide a conductive three-dimensional architecture that was demonstrated for application in microbial fuel cell (MFC) anodes. Composite electrodes from PHBV were fabricated to defined dimensions by solvent casting and particulate leaching of a size-specific porogen (in this case, sucrose).

Fabrication of macroporous chitosan scaffolds doped with carbon nanotubes and their characterization in microbial fuel cell operation.

Chitosan (CHIT) scaffolds doped with multi-walled carbon nanotubes (CNT) were fabricated and evaluated for their utility as a microbial fuel cell (MFC) anodic material. High resolution microscopy verified the ability of Shewanella oneidensis MR-1 to directly colonize CHIT-CNT scaffolds. Cross-linking agents 1-ethyl-3-[3-dimethylaminopropyl] carbodimide hydrochloride (EDC), glutaraldehyde and glyoxal were independently studied for their ability to strengthen the CHIT-CNT matrix without disrupting the final pore structure.

Engineering of glucose oxidase for direct electron transfer via site-specific gold nanoparticle conjugation.

Optimizing the electrical communication between enzymes and electrodes is critical in the development of biosensors, enzymatic biofuel cells, and other bioelectrocatalytic applications. One approach to address this limitation is the attachment of redox mediators or relays to the enzymes. Here we report a simple genetic modification of a glucose oxidase enzyme to display a free thiol group near its active site.

Enzymatic fuel cells: integrating flow-through anode and air-breathing cathode into a membrane-less biofuel cell design.

One of the key goals of enzymatic biofuel cells research has been the development of a fully enzymatic biofuel cell that operates under a continuous flow-through regime. Here, we present our work on achieving this task. Two NAD(+)-dependent dehydrogenase enzymes; malate dehydrogenase (MDH) and alcohol dehydrogenase (ADH) were independently coupled with poly-methylene green (poly-MG) catalyst for biofuel cell anode fabrication.

Engineering of a redox protein for DNA-directed assembly.

Engineered enzyme conjugate of the small laccase enzyme from Streptomyces coelicolor and zinc finger DNA binding domain from Zif268 is demonstrated to bind double stranded DNA in a site specific manner while retaining enzymatic activity.

Standardized microbial fuel cell anodes of silica-immobilized Shewanella oneidensis.

Populations of metabolically active bacteria were associated at an electrode surface via vapor-deposition of silica to facilitate in situ characterization of bacterial physiology and bio-electrocatalytic activity in microbial fuel cells.

Fluorescence analysis of chemical microenvironments and their impact upon performance of immobilized enzyme.

In this work the shift in fluorescence emission spectra of acrylodan, a polar sensitive fluorophore, has been used to characterize the polarity immediately surrounding cytoplasmic (cMDH) and mitochondrial malate dehydrogenase (mMDH) enzyme immobilized within three-dimensional macroporous chitosan scaffolds. The scaffolds were fabricated from solutions of fluorescently tagged enzymes mixed with deacetylated and hydrophobically modified chitosan polymer. Each solution was frozen and then freeze-dried through the process of thermally induced phase separation (TIPS).

Conductive macroporous composite chitosan-carbon nanotube scaffolds.

Multiwalled carbon nanotubes (MWCNTs) were used as doping material for three-dimensional chitosan scaffolds to develop a highly conductive, porous, and biocompatible composite material. The porous and interconnected structures were formed by the process of thermally induced phase separation followed by freeze-drying applied to an aqueous solution of 1 wt % chitosan acetic acid. The porosity was characterized to be 97% by both mercury intrusion porosimetry measurements and SEM image analysis.

Improved specificity of reagentless amperometric PQQ-sGDH glucose biosensors by using indirectly heated electrodes.

Indirectly heated electrodes operating in a non-isothermal mode have been used as transducers for reagentless glucose biosensors. Pyrroloquinoline quinone-dependent soluble glucose dehydrogenase (PQQ-sGDH) was entrapped on the electrode surface within a redox hydrogel layer. Localized polymer film precipitation was invoked by electrochemically modulating the pH-value in the diffusion zone in front of the electrode.

Application of heated electrodes operating in a non-isothermal mode for interference elimination with amperometric biosensors.

Heated electrodes were applied for the non-isothermal operation of amperometric glucose biosensors based on glucose oxidase immobilised on the electrode surface by entrapment within a polymer layer. The localised deposition of the polymer film under simultaneous entrapment of the enzyme was achieved by an electrochemically induced pH-modulation in the diffusion zone in front of the electrode, thus altering the solubility of the polymer chains. This non-manual sensor preparation protocol could be successfully used for the modification of a novel indirectly heated electrode.