Kinetic mathematical model for ketone bioconversion using Escherichia coli TOP10 pQR239

• A non-reported pseudo intrinsic kinetic model was developed on basic reactions.
• The reaction mechanism proposed followed the formalism of Langmuir–Hinshelwood.
• Complexes formation of substrate inhibition and oxygen inactivation are accounted.
• Affinity and inhibition constants were obtained from the kinetic model.
• This is the first report for oxygen inactivation constant (22.3 μM).

The aim of the current work was to develop a pseudo intrinsic kinetic model, based on elementary reactions, to describe the behavior of the bioconversion of ketones using Escherichia coli TOP10 pQR239. Since there are no reports of the oxygen inactivation constant in the literature, this study gave new insights to find optimal conditions of a suitable oxygen supply during the bioconversion. In this model the reaction mechanism proposed followed the formalism of Langmuir–Hinshelwood and considered both substrate inhibition and oxygen inactivation by the formation of intermediary complexes. Therefore, approximations of the pseudo equilibrium of reaction rates or steady state intermediary species were not considered, which allowed for identifying the role of each reaction step involved in the bioconversion. This kinetic model adequately described the observations with and without substrate inhibition and/or oxygen inactivation. And the regression and the estimated parameters were statistically significant, making these analyses reliable regarding the kinetic behavior of CHMO. Then, substrate and oxygen affinity and inhibition constants were obtained from the kinetic parameters of the model. It was observed that oxygen and substrate presented similar affinity constant values. The substrate inhibition (KIS) and oxygen inactivation (KIO2) constants were determined to be 9.98 μM and 22.3 μM, respectively, showing that the CHMO enzyme was twice more sensitive to inhibition by an excess of substrate than oxygen.