2.10. Sulphite oxidase-containing tissues
Sulphite is widely used as an additive in food and beverages to prevent oxidation and bacterial growth. However, sulphite content is strictly limited due to the reported harmful effects on hypersensitive people. Malva vulgaris has been used as sulphite oxidase source for the development of an electrochemical sulphite biosensor (Sezgintürk and Dinçkaya, 2005). This enzyme catalyses the final reaction in oxidative degradation of the sulphur-containing amino acids cysteine and methionine, producing hydrogen peroxide. The oxygen consumed was monitored by amperometry, and the signal related to the sulphite concentration. Although the tissue-based biosensor presented a limit of detection (0.2mM)lower than the conventional pure enzyme-based biosensors, immobilisation protocols were easier and costs lower.