Immobilized cyanobacteria on the cathode as oxygen source for microbial fuel cell

Oxygen is commonly used as the electron acceptor for the cathode reaction in microbial fuel cells (MFCs). This study demonstrates how to generate oxygen via photosynthesis by means of Synechocystis AICB 51 cyanobacteria immobilized on the cathode. The advantage of using cyanobacteria immobilized on the cathode was demonstrated using two geometries: two-chamber and membrane-less MFCs. The anode chamber was filled with sludge collected from the wastewater treatment plant from Cluj-Napoca, Romania. The oxygen concentration in the cathode space of two-chamber cells rises from about 1mg [l.sup.-1] at 130 lux to 11 mg [l.sup.-1] at 2500 lux of incident illumination. In the case of membrane-less cells, the oxygen concentration varies from 0.2mg [l.sup.-1] to 4.5 mg [l.sup.-1] for the same conditions of illumination. In the case of membrane-less MFCs, the power generated with the immobilized cyanobacteria on the cathode is up to 20 of times greater than the power generated with the standard plain graphite cathode during illumination. In both cases there is a strong correlation between power and dissolved oxygen concentration. Keywords: immobilized Synechocystis cyanobacteria, microbial fuel cell, photosynthetic oxygen, dissolved oxygen, power density