Bacterial membrane electrode for l-cysteine

Potentiometric response to L-cysteine is obtained by coupling bacteria of the type Proteus morganii to a modified version of a hydrogen sulfide gas-sensing membrane electrode. The resulting electrode system shows good response to cysteine in the millimolar concentration range with moderate selectivity over related sulfur-containing amino acids. The practical applicability of the electrode is limited by the poor discrimination of the internal gas sensor between hydrogen sulfide and carbon dioxide.