Investigation of baker’s yeast Saccharomyces cerevisiae- and mediator-based carbon paste electrodes as amperometric biosensors for lactic acid

Carbon paste electrodes modified with baker’s yeast (a source of cytochrome b2) and various mediators (Nile blue, methylene blue, toluidine blue, Meldola blue, p-hydroquinone and Prussian Blue) were tested for the sensitivity to lactic acid. Electrochemical activity of mediators increased when baker’s yeast was added to the paste. Only Meldola blue and Prussian Blue-modified electrodes responded to lactic acid. The operating potentials were +0.1 and +0.3 V (versus saturated Ag/AgCl), respectively. A linear range in the dependence of the current response upon the concentration of lactic acid was up to 1 mM. Electrode sensitivity and apparent Michaelis constants (KM′) decreased with aging of the yeast.