Growth kinetics of Chlorella vulgaris and its use as a cathodic half cell

The kinetics of growth of the algal species Chlorella vulgaris has been investigated using CO2 as the growth substrate. The growth rate was found to increase as the dissolved CO2 increased to 150 mg/L, but fell dramatically at higher concentrations. Increasing the radiant flux also increased growth rate. With a radiant flux of 32.3 mW falling directly on the 500 mL culture media, the growth rate reached up to 3.6 mg of cells/L-h. Both pH variation (5.5–7.0) and mass transfer rate of CO2 (KLa between 6 h−1 and 17 h−1) had little effect on growth rate. Growing on glucose, the yeast Saccharomyces cerevisiae produced a stable 160 mV potential difference when acting as a microbial fuel cell anode with ferricyanide reduction at the cathode. The algal culture was observed to be a workable electron acceptor in a cathodic half cell. Using an optimum methylene blue mediator concentration, a net potential difference of 70 mV could be achieved between the growing C. vulgaris culture acting as a cathode and a 0.02 M potassium ferrocyanide anodic half cell. Surge current and power levels of 1.0 μA/mg of cell dry weight and 2.7 mW/m2 of cathode surface area were measured between these two half cells.