Stabilized bacteria-based potentiometric electrode for pyruvate

Abstract A bacteria-based potentiometric electrode is described which demostrates a strategy for adapting an unstable enzyme system for use as a practical biocatalyst. Streptococcus faecium (ATCC 9790), containing the pyruvate dehydrogenase multienzyme complex, serves to convert pyruvate to carbon dioxide, which is detected by a gas-sensing electrode. The probe has an average slope of 41 m V per concentration decade over a range from 2.2 × 10 −4 to 3.2 × 10 −2 M pyruvate, and a lowe limit of detection of 1.3 × 10 −4 M pyruvate. Response times varied from 6–9 min for a new electrode to a maximum of 8—12 min during the probe lifetime of two weeks. Electode storage at 4°C in pH 5.5 buffer containing phosphate anions was critical optimal probe response characteristics. The Streptococcu faecium electrode is compared and contrasted with other potentiometric pyruvate electrodes reported employing isolated enzyme, dual enzyme—cofactor, or plant tissue biocatalysts.