Direct and Indirect Solar Energy Utilization in Bioelectrochemical Cells

The Effect of glucose addition on the current outputs of the electrochemical cells using Synechocystis sp. PCC6714 was investigated under the conditions with or without light. The current outputs increased with higher concentrations of HNQ and glucose. The current under illumination was lower than that in the dark even in the presence of 5 mM HNQ and 1 g 1⁻¹ glucose, or 1 mM HNQ and 10 g 1⁻¹ glucose. However, the coulombic output obtained from integration of the current was higher under illumination than in the dark under the conditions with 5 mM HNQ and 10 g 1⁻¹ glucose. A main organic acid produced during discharge was acetic acid. The amount of acetic acid decreased, when the current outputs increased. Therefore, the current output production might compete with the production of acetic acid. Efficient system could be established by supplying both solar energy and chemical energy simultaneously.