Sulphate reducing bacteria - electroactive biofilm formation

The formation of biofims from a pure strain of sulphate reducing bacteria (SRB), Desulfovibrio desulfuricans 27774, on different materials, namely, stainless steel and graphite, on polarised and non-polarised surfaces were studied. Different times and polarisation conditions were attempted. A value of -0.4 V vs SCE was observed to be the most effective concerning the formation of an electroactive biofilm and cathodic currents due to biofilm growth were observed with a maximum intensity of -270 mA m^-2. These cathodic currents remained stable for several days using graphite electrodes. Anodic polarisation was not successfully observed using this bacterial strain. The SRB biofilm present electrocatalytic activity towards hydrogen and oxygen reduction reactions and it was observed that the electrode polarisation conditions have a selective effect on the catalytic activity. Hydrogenase activity in SRB was invoked to explain the electroactivity of these SRB biofilms.