Current and voltage responses in instant photosynthetic microbial cells with Spirulina platensis

The electrical response of photosynthetic microbial cells (PMCs) containing Spirulina platensis was investigated to assess the feasibility of using these PMCs as instant-use and portable devices. The PMCs were constructed without membranes, mediators, or any additive organic substrates. Once S. platensis was attached to an anode, voltage was instantly obtained and ready for application. Since no additional substrate was required as fuel for electricity generation, these PMCs were different from typical microbial fuel cells. PMCs were examined under various operating conditions, and they performed under high open circuit voltage (OCV) with high power output in the dark, short electrode spacing (2 cm), low pH value (5.5), and high temperature (40 °C) conditions. According to Ohm's Law and the Nernst equation, the superior OCV and power output were caused by high ionic strength, low internal resistance, and high temperature. Additionally, two equal-sized PMCs were arranged in serial and parallel configurations. The former yielded higher voltage while the latter yielded higher current density.