Separate immobilization of glucose oxidase and trehalase, and optimization of enzyme-carbon nanotube layers for the anode of enzymatic fuel cells utilizing trehalose

Abstract

Insect cyborgs can be used as search robots in disaster areas and as environmental monitoring robots. In this study, we aimed to develop an anode for compact enzymatic fuel cells (EFCs) utilizing trehalose to power electronic devices implanted in such insects. Conventional trehalose-EFCs are fabricated by coimmobilization of glucose oxidase (GOx) and trehalase (TREH) on the surface of the anode. Here, we showed that current generation can be enhanced by separate immobilization of GOx and TREH using agarose. The effects of GOx-redox mediator layers, TREH loading, and the incorporation of single-walled carbon nanotubes (SWCNTs) on the performance of GOx-TREH anodes were investigated. The optimal arrangement of GOx-redox mediator layers with or without SWCNTs was determined. The highest oxidation current density (494 mu A/cm(2)) was obtained at an electrode composed of three GOx-redox mediator layers and three GOx-redox mediator-SWCNTs layers, and agarose containing TREH. The bilirubin oxidase (BOD)-redox mediator layers and SWCNTs also influenced the performance of cathode. The highest reduction current intensity was obtained for the cathode with six BOD-redox mediator-SWCNTs layers. EFCs with the optimized anode and cathode showed a power density of ca. 15 mu W/cm(2) at a cell voltage of 0.3 V under a discharge current density of 50 mu A/cm(2) . (C) 2021 Elsevier Ltd. All rights reserved.