Cellobiose dehydrogenase hosted in lipidic cubic phase to improve catalytic activity and stability

Lipidic cubic phase systems (LCPs) are excellent carriers for immobilized enzymes due to their biocompatibility and well-defined nanoporous structure. Lipidic cubic phases act as a convenient matrix to incorporate enzymes and hold them in the vicinity of electrode surfaces in their fully active forms. Corynascus thermophilus cellobiose dehydrogenase (CtCDH) was trapped in a monoolein cubic phase, which increased not only its stability, but also its catalytic performance with both enhanced mediated and direct electron transfer with electrodes. For studies of mediated electron transfer, three mediators with different formal potentials (E°') were employed: horse-heart cytochrome c (cyt c), electron acceptor active with the cytochrome domain of CtCDH, and 2,6-dichlorophenolindophenol (DCPIP) as well as hexaammineruthenium(II) chloride [Ru(NH₃)Cl₂] both electron acceptors with the dehydrogenase domain. Ru(NH₃)Cl₂, having the most negative E°' of -0.138V vs. Ag|AgCl at pH7.5, gave a catalytic current for lactose oxidation of 32.10μAcm^-2 in MOPS buffer at pH7.5. The process carried out in the same solution but under direct electron conditions transfer resulted in a catalytic current of 9.22μAcm^-2. Electrodes covered with CtCDH in a LCP film retained their catalytic activity after 28days showing a slightly increased current density after 6days.