Seven choline sulfonates with buffering properties were developed. Cytochrome c solubility and redox ability were evaluated in these choline sulfonate buffers.

Ionic liquids have been attracting considerable interest in wide diverse fields, including biotechnology applications. Metalloproteins' stability in such media is still a controversial subject. Divergent reports on the metalloproteins' stability have been published, although hydrated ionic liquids seem more beneficial for achieving efficient redox transitions with the proteins' redox centers. In the present study the electrochemical behavior of Cyt c in three choline-based ionic liquids aqueous solutions, namely choline dehydrogenophosphate ([Ch][DHP]), choline 2-(N-morpholino)ethanesulfonic acid ([Ch][MES]) and choline 3-(cyclohexylamino)-1-propanesulfonic acid ([Ch] [CAPS]) was investigated. Cyt c formal potential and its temperature dependence, the diffusion coefficient and heterogeneous electron transfer rate were evaluated by cyclic voltammetry. The results show that Cyt c in aqueous solutions of [Ch][DHP] and [Ch][MES], retain its intrinsic redox properties.

Highlights Electricity production by biocathode containing MFC in long-term operation. Biocathodes shows overall advantages over abiotic cathodes. Voltammetric analysis supports a more sustainable electron transfer using biocathodes. PCR-RFLP analysis identified potential electricity producing organims.