Amperometric determination of acetic acid with a trienzyme/poly(dimethylsiloxane)-bilayer-based sensor

A trienzyme sensor for the amperometric determination of acetic acid was pr epared by immobilizing acetate kinase (AK), pyruvate kinase (PK), and pyruv ate oxidase (PyOx) on a poly(dimethylsiloxane) (PDMS)-coated electrode. AK catalyzes the phospho-transferring reaction between acetic acid and ATP to form ADP; PK, the phospho-transferring reaction between ADP and phosphoenol pyruvate to form pyruvic acid; and PyOx, the oxidation of pyruvic acid with oxygen. The oxygen consumption could be monitored by using the PDMS-coated electrode without interference from the PyOx reaction product, hydrogen pe roxide. Thus, the concentration of acetic acid (5 muM-0.5 mM) could be dete rmined from the decrease in the cathodic current at -0.4 V vs Ag/AgCl. This is the first example of a biosensor that can be used for the determination of acetic acid in ethanol-containing food samples. The acetate-sensing ele ctrode could be used for more than one month.