Marcelinus Christwardana

Fabrication of Mediatorless/Membraneless Glucose/Oxygen Based Biofuel Cell using Biocatalysts Including Glucose Oxidase and Laccase Enzymes

Mediatorless and membraneless enzymatic biofuel cells (EBCs) employing new catalytic structure are fabricated. Regarding anodic catalyst, structure consisting of glucose oxidase (GOx), poly(ethylenimine) (PEI) and carbon nanotube (CNT) is considered, while three cathodic catalysts consist of glutaraldehyde (GA), laccase (Lac), PEI and CNT that are stacked together in different ways. Catalytic activities of the catalysts for glucose oxidation and oxygen reduction reactions (GOR and ORR) are evaluated. As a result, it is confirmed that the catalysts work well for promotion of GOR and ORR. In EBC tests, performances of EBCs including 150 μm-thick membrane are measured as references, while those of membraneless EBCs are measured depending on parameters like glucose flow rate, glucose concentration, distance between two electrodes and electrolyte pH. With the measurements, how the parameters affect EBC performance and their optimal conditions are determined. Based on that, best maximum power density (MPD) of membraneless EBC is 102 ± 5.1 μW · cm−2 with values of 0.5 cc · min−1 (glucose flow rate), 40 mM (glucose concentration), 1 mm (distance between electrodes) and pH 3. When membrane and membraneless EBCs are compared, MPD of the membraneless EBC that is run at the similar operating condition to EBC including membrane is speculated as about 134 μW · cm−2.

Yeast and carbon nanotube based biocatalyst developed by synergetic effects of covalent bonding and hydrophobic interaction for performance enhancement of membraneless microbial fuel cell

Membraneless microbial fuel cell (MFC) employing new microbial catalyst formed as yeast cultivated from Saccharomyces cerevisiae and carbon nanotube (yeast/CNT) is suggested. To analyze its catalytic activity and performance and stability of MFC, several characterizations are performed. According to the characterizations, the catalyst shows excellent catalytic activities by facile transfer of electrons via reactions of NAD, FAD, cytochrome c and cytochrome a3, while it induces high maximum power density (MPD) (344mW·m-2). It implies that adoption of yeast induces increases in catalytic activity and MFC performance. Furthermore, MPD is maintained to 86% of initial value even after eight days, showing excellent MFC stability.

Highly sensitive glucose biosensor using new glucose oxidase based biocatalyst

Glucose, which is a primary energy source of living organisms, can induce diabetes or hypoglycemia if its concentration in blood is irregular. It is therefore important to develop glucose biosensor that reads the concentration of glucose in blood precisely. In the present work, we suggest new glucose oxidase (GOx) based catalysts that can improve the sensitivity of the glucose biosensor and make glucose measurements over a wide concentration ranges possible. For synthesizing such catalysts, a composite including pyrenecarboxaldehyde (PCA) and GOx is attached to substrate including carbon nanotube (CNT) and polyethyleneimine (PEI) (CNT/PEI/[PCA/GOx]). Catalytic activity and stability of the catalyst are then evaluated. According to the investigation, the catalyst shows excellent glucose sensitivity of 47.83 μAcm−2mM−1, low Michaelis-Menten constant of 2.2 mM, and wide glucose concentration detection, while it has good glucose selectivity against inhibitors, such as uric acid and ascorbic acid. Also, its activity is maintained to 95.7% of its initial value even after four weeks, confirming the catalyst is stable enough. The excellence of the catalyst is attributed to hydrophobic interaction, C=N bonds, and π-hydrogen interaction among GOx, PCA and PEI/CNT. The bindings play a role in facilitating electron transport between GOx and electrode.

A correlation of results measured by cyclic voltammogram and impedance spectroscopy in glucose oxidase based biocatalysts

A new biocatalyst consisting of glucose oxidase (GOx) and polyethylenimine (PEI) immobilized on carbon nanotube (CNT) (CNT/PEI/GOx) was developed, while cyclic voltammogram (CV) behaviors of several related catalysts including the CNT/PEI/GOx were analyzed in terms of charge transfer resistances (Rcts) obtained by measuring Nyquist plots using electrochemical impedance spectroscopy (EIS). A qualitative correlation between the flavin adenine dinucleotide (FAD) redox reactivity measured by the CV and Rct was established. As factors affecting both the FAD reactivity and Rct, concentrations of GOx, glucose, and phosphate buffer solution, electrolyte pH and ambient condition were considered and evaluations of the catalysts using the CV curves and Nyquist plots confirmed that a pattern in the FAD reactivity was closely linked to that in the Rct, implying that FAD reactivities of the catalysts are predicted by the measurements of their Rcts. Even regarding performance of the enzymatic biofeul cells (EBCs) using the reacted catalysts, a pattern of the Rcts is compatible with that in the maximum power densities (MPDs) of the EBCs.

Combination of physico-chemical entrapment and crosslinking of low activity laccase-based biocathode on carboxylated carbon nanotube for increasing biofuel cell performance

New laccase-based catalysts to improve oxygen reduction reactions (ORR) are described, and enzymatic biofuel cells (EBCs) adopting these catalysts were developed. These new catalysts are synthesized by combining laccase, poly(ethylenimine) and carbon nanotubes, with attachment of selected elements using the crosslinker, glutaraldehyde (GA). Several characterization approaches are implemented to evaluate catalytic electron transfer in both the absence and presence of mediators and their effects on glucose/O2 biofuel cell performance. [CNT/Lac/PEI/Lac]/GA shows that the best electron transfer rate constants (ks) achieved, in the presence as well as the absence of a mediator, are 8.6 and 1.8s-1. Additionally, [CNT/Lac/PEI/Lac]/GA results in high performance of Maximum Power Density with a value of 0.2mWcm-2. Its relative stability can be maintained up to 83.76% with relative efficiency up to 84.73%, while CNT/Lac gives the lowest performance levels. This indicates that GA induces an improvement in catalytic activity by (i) increasing the amount of immobilized laccase and (ii) strengthening interaction between laccase and PEI. Therefore, it induces excellent redox reactivity, promoting the ORR, and glucose/O2 biofuel cell performance. The effect of pH on catalytic activity is also measured, with pH 5 being optimal.