In this study, we immobilize glucose oxidase (GOx) using two different enzyme immobilization techniques. First, nanoscale enzyme reactors (NERs) of GOx in conductive mesoporous carbons were prepared in a two-step process of enzyme adsorption and follow-up enzyme crosslinking. MSU-F-C, a mesoprous carbon, has a bottleneck pore structure with mesocellular pores of 26 nm connected with window mesopores of 17 nm. This structure enables the ship-in-a-bottle mechanism of NERs, which effectively prevents the crosslinked enzymes in mesocellular pores from leaching through the smaller window mesopores. Secondly, highly stable enzyme precipitate coatings (EPCs) on carbon nanotubes (CNTs) were prepared by precipitating GOx molecules in the presence of ammonium sulfate, then cross-linking the precipitated GOx aggregates on covalently attached enzyme molecules on the surface of CNTs. We used these NERs and EPCs of GOx as the enzyme electrode for both biosensor and biofuel cell applications. In this paper, their electrochemical performances and stability will be tested in terms of their sensitivity for detecting GOx and power density output for converting GOx into electrical power.