Exploring the possibility of predicting CALB activity in liquid organic medium, with the aid of intrinsic kinetic parameters and intrinsic solvent effect data obtained in solid/gaz reactor

Abstract

In organic solvents the activity of enzyme is often order of magnitude lower than in water solutions and varies significantly with the solvent used. Many attempts to quantify and model the decrease of enzyme catalytic efficiency in solvents have been performed, but still there is no general method for predicting enzyme activity in a particular solvent in absolute terms. In this paper, a new method is proposed to predict initial reaction rates in different anhydrous monophasic liquid organic media, in the case of CALB-catalyzed alcoholysis reaction. The experimental tool used for this method is a solid/gas bioreactor, which allows to obtain enzyme intrinsic kinetic parameters and intrinsic effect of organic solvents on enzyme activity. It is shown that, once corrections for solvation of substrates have been performed, the effect of solvent molecules consists mainly on binding to enzyme active site, leading to competitive inhibition of solvent towards the first substrate ester. The intrinsic parameters obtained in solid/gas reactor are used to predict activity of different batches of CALB, in organic media of different polarities, based on a single rate measurement in hexane. The result is a right prediction of solvent order with regard to CALB activity, a proper approximation of initial rate for weakly inhibiting solvents and overestimation for solvents showing a marked inhibitor character.