In Silico Analysis of Glucose Oxidase H516r and H516d Mutations for an Enzymatic Fuel Cell

Glucose oxidase (GOx) is an oxido-reductase enzyme that catalyzes glucose into hydrogen peroxide and glucono delta-lactone (GDL). GOx has the potential to be used in the medical field. Numerous research concerning the usage of GOx to create enzymatic biofuel cells have been done, nevertheless the results obtained have not been optimal. This research aims to increase the Km values of GOx in order to increase its potential as a material for an enzymatic fuel cell. The amino acid histidine in position 516 is a residue in the active site that plays an important part in the process of glucose oxidation. In this research we mutated H516 by in silico twice resulting in the mutants R516 and D516. The mutations resulted in a change of the docking area for both mutants and in the docking affinity for H516D resulting in higher Km values. This shows that the H516 residue plays an important part in the functions of glucose oxidase and mutation into aspartate could improve glucose oxidase based enzymatic fuel cells.

A Hybrid Microbial–Enzymatic Fuel Cell Cathode Overcomes Enzyme Inactivation Limits in Biological Fuel Cells

The construction of optimized biological fuel cells requires a cathode which combines the longevity of a microbial catalyst with the current density of an enzymatic catalyst. Laccase-secreting fungi were grown directly on the cathode of a biological fuel cell to facilitate the exchange of inactive enzymes with active enzymes, with the goal of extending the lifetime of laccase cathodes. Directly incorporating the laccase-producing fungus at the cathode extends the operational lifetime of laccase cathodes while eliminating the need for frequent replenishment of the electrolyte. The hybrid microbial–enzymatic cathode addresses the issue of enzyme inactivation by using the natural ability of fungi to exchange inactive laccases at the cathode with active laccases. Finally, enzyme adsorption was increased through the use of a functionally graded coating containing an optimized ratio of titanium dioxide nanoparticles and single-walled carbon nanotubes. The hybrid microbial–enzymatic fuel cell combines the higher current density of enzymatic fuel cells with the longevity of microbial fuel cells, and demonstrates the feasibility of a self-regenerating fuel cell in which inactive laccases are continuously exchanged with active laccases.

Recent Advances in the Direct Electron Transfer-Enabled Enzymatic Fuel Cells

Direct electron transfer (DET), which requires no mediator to shuttle electrons from enzyme active site to the electrode surface, minimizes complexity caused by the mediator and can further enable miniaturization for biocompatible and implantable devices. However, because the redox cofactors are typically deeply embedded in the protein matrix of the enzymes, electrons generated from oxidation reaction cannot easily transfer to the electrode surface. In this review, methods to improve the DET rate for enhancement of enzymatic fuel cell performances are summarized, with a focus on the more recent works (past 10 years). Finally, progress on the application of DET-enabled EFC to some biomedical and implantable devices are reported.

Stability of Proton Exchange Membranes in Phosphate Buffer for Enzymatic Fuel Cell Application: Hydration, Conductivity and Mechanical Properties

Proton-conducting ionomers are widespread materials for application in electrochemical energy storage devices. However, their properties depend strongly on operating conditions. In bio-fuel cells with a separator membrane, the swelling behavior as well as the conductivity need to be optimized with regard to the use of buffer solutions for the stability of the enzyme catalyst. This work presents a study of the hydrolytic stability, conductivity and mechanical behavior of different proton exchange membranes based on sulfonated poly(ether ether ketone) (SPEEK) and sulfonated poly(phenyl sulfone) (SPPSU) ionomers in phosphate buffer solution. The results show that the membrane stability can be adapted by changing the casting solvent (DMSO, water or ethanol) and procedures, including a crosslinking heat treatment, or by blending the two ionomers. A comparison with NafionTM shows the different behavior of this ionomer versus SPEEK membranes.

A Hybrid Microbial-Enzymatic Fuel Cell Cathode Overcomes Enzyme Inactivation Limits in Biological Fuel Cells

The construction of optimized biological fuel cells requires a cathode which combines the longevity of a microbial catalyst with the power density of an enzymatic catalyst. Laccase secreting fungi were grown directly on the cathode of a biological fuel cell to facilitate the exchange of inactive enzymes with active enzymes with the goal of extending the lifetime of laccase cathodes. Additionally, a functionally graded coating was developed to increase enzyme loading at the cathode. Directly incorporating the laccase producing fungus at the cathode extends the operational lifetime of laccase cathodes while eliminating the need for frequent replenishment of the electrolyte. Additionally, the hybrid microbial-enzymatic cathode addresses the issue of enzyme inactivation by using the natural ability of fungi to exchange inactive laccases at the cathode with active laccases. Finally, enzyme adsorption was increased through the use of a functionally graded coating containing an optimized ratio of titanium dioxide nanoparticles and single walled carbon nanotubes. The hybrid microbial-enzymatic fuel cell combines the higher power density of enzymatic fuel cells with the longevity of microbial fuel cells and demonstrates the feasibility of a self-regenerating fuel cell in which inactive laccases are continuously exchanged with active laccases.

Characteristics of Glucose Oxidase Gene (GGOx) from Aspergillus niger IPBCC 08.610

Glucose oxidase is used in various industries for the development of enzymatic fuel cell. Based on prior studies, this compound is sourced from the local isolates of Aspergillus niger IPBCC 08.610, although investigations on the encoding gene have not been conducted. The purpose of this research, therefore, is to identify and characterized the gene responsible for encoding glucose oxidase, in the aspect of sequence, length, and restriction patterns. This experiment involved the amplification of genomic DNA using specific primers for gene recognition, which was followed by the restriction technique with EcoRI and PstI endonucleases. Furthermore, the gene is inserted into vector pGEM®T-Easy and transformed into competent E. coli DH5α cells, in an attempt to perform sequencing. The glucose oxidase gene from A. niger IPBCC 08.610 was confirmed to possess a size of 1848 bp, and a GC content of 57.8%, with a possibility of restriction into two fragments of size 908 bp and 980 bp, using the EcoRI restriction.

Direct Methanol Catalytic Fuel Cell, for Measuring Ethanol Contents in Pharmaceutical Tinctures

Background: In order to test real direct applicability for analytical purposes, a small and simple direct methanol (or ethanol) catalytic, enzymatic or non-enzymatic fuel cell (DMFC) was used for the analysis of ethanol-based pharmaceutical tinctures; a detailed experimental study was conducted on five different pharmaceutical tinctures available at drugstores. Results: The results obtained using both enzymatic and non-enzymatic devices were compared with those obtained by analyzing the same pharmaceutical samples with a conventional catalase biosensor. Finally, the results were compared with the nominal values provided by manufacturing firms. Conclusion: The correlations between the different experimental and nominal values considered were good in general or satisfactory and the applied statistical tests (f-test and t-test) were also very comforting. At the end of the study, the use of enzymatic DMFC proved to be better than non- enzymatic DMFC devices, because it requires shorter analysis times.