A mathematical model of oxidative deamination of amino acid catalyzed by two D-amino acid oxidases and influence of aeration on enzyme stability.

Two D-amino acid oxidases (DAAO) from different sources (Arthrobacter protophormiae and porcine kidney) were used to oxidatively deaminate D-methionine in the batch reactor. A mathematical model of the process was developed and validated by the experiments carried out without and with oxygen supply by aeration. Kinetic parameters of the model were estimated from the initial reaction rate experiments. Aeration increased the reaction rate in the initial part of the reaction and reduced the time necessary to achieve the final substrate conversion. However, it had a negative influence on the operational stability of enzymes. Operational stability decay rate constants estimated from the experimental data increased with the airflow rate, which indicated lower operational stability of enzymes. It was found that oxygen concentration significantly influenced the stability of DAAO from porcine kidney. Enzyme from microbial source had better operational stability and one order of magnitude lower values of decay rate constants.