OPTIMIZATION OF BIOCATHODES: BIOCHAR AS ELECTRODE MATERIAL FOR GROWTH OF ELECTROACTIVE BACTERIA

ANTIC GORRAZZI, SOFIA; MASSAZZA, DIEGO; PEDETTA, ANDREA; BUSALMEN J.P.; BONANNI P. SEBASTIAN

Los Cocos, Cordoba

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Sociedad Argentina de Microbiología General

Cathodic electro-active microorganisms can use an electrode as electron donor to reduce, nitrates, sulfates or chlorinated compounds. In this context, the electrode acts as an inexhaustible electron source that enhances microorganisms activity, allowing numerous applications related with biocatalysis, biosynthesis and wastewater treatment. However, their application has been relegated due to the low current density they produce. The performance of bioelectrochemical systems depends mainly on the ability and efficiency of microorganisms to adhere and exchange electrons with the polarized surface. The current density obtained on biocathodes may be limited by an adverse bacterial adherence on the electrode surface caused by electrostatic repulsion between the bacteria and the electrode. Still, basic studies are required to improve the interaction between electroactive microorganisms and electrodes. Growth medium parameters such as ionic strength, presence of organic compounds, pH, flow rate, and temperature have been shown to affect adherence of bacteria to surfaces. On the other hand, material and surface properties such as hydrophobicity and electrostatic charge also play a fundamental role in the biofilm formation process. Previously, we found that biochar, a carbonaceous compound obtained through the pyrolysis of biomass, has electrochemical properties that improve bacteria-electrode interaction. Biochar electrodes obtained at relatively low temperatures (600/800ºC) enhance current density produced by G. sulfurreducens on anodes. Because the biochar has charged organic functional groups on its surface that could improve initial attachment of cathodic bacteria to electrodes, we test it as cathode material in electrochemical cells. Biochar electrodes of different temperatures (500ºC-1200ºC) were polarized at -0,3V vs SHE and growth of cathodic bacteria Thiobacillus denitrificans was followed by measuring the electric current through chronoamperometry. Scanning microscopy images were taken to analyze bacterial coverage. In agreement with previous results with anodic bacterias, higher current densities were registered when biochars obtained at 600ºC/800ºC were used as cathodes. Current densities values were comparable to those obtained with graphite, the most common electrode material used for the growth of electroactive bacteria. This results not only provided information to optimize biocathode performance, but also reinforces the evidence that biochar could be a cheap and ecofriendly electrode material, which revalues waste.