An l-amino acid electrode for monitoring beer fermentation

A membrane covered amperometric l-amino acid electrode is described, employing l-amino acid oxidase immobilized on a Pt disc electrode with rabbit albumin and glutaraldehyde. The electrode response to a range of l-amino acids and a theoretical treatment for the rate determining step are presented. Results are also given for the application of the electrode in monitoring beer fermentations. Appropriate amino acid utilisation is vital for both yeast cell growth and beer flavour development.List of symbols A electrode area - D diffusion coefficient - e reduced enzyme concentration - e total enzyme concentration - F Faraday constant - i electrode current - i_D l/A - I l/k_ME - j flux - L thickness of the electrolyte layer - L _M thickness of the membrane - k_cat rate constant for enzyme/substrate reaction - k rate constant for electrode reaction - k_ME electrochemical rate constant for the enzyme reaction - k_S mass transfer rate constant for substrate in membrane - K membrane constant - K _s partition coefficient of substrate in membrane - K_M Michaelis constant - n number of electrons S substrate - Ii_D/S] - y (^–1 – 1)/S]