Development of a photoelectrochemical sensor for monitoring algal biomass (Chlorella vulgaris)

Herein, we present a novel photoelectrochemical sensor system for the rapid enumeration of algal biomass. The photosynthesis-based reducing action of algal cells on the electrochemical mediator 2-hydroxyl-1,4-naphthoquinone (HNQ) was used as the basis of an amperometric sensor system. By using a simple LED (Light-Emitting Diode) installed three-electrode cell, the mediator that was reduced by algal metabolic activity was reoxidized at a platinum-working electrode and held at a positive potential. In the presence of CO2 as an electron donor, and LED illumination as an energy source for the algal cells, the reoxidation current and its rate of increase were found to depend on the concentration of algal biomass. Regression analyses plotting the initial rate of current (μA min−1) against algal biomass concentrations (g L−1) produced a reasonable correlation coefficient (r2 = 0.9938). The sensor system exhibited a high sensitivity to algal biomass at a concentration as low as 0.065 g L−1and a rapid response time, which is promising for further applications of the sensor system in algal-related industries.