Development of a process model to describe the synthesis of (R)‐mandelonitrile by Prunus amygdalus hydroxynitrile lyase in an aqueous–organic biphasic reactor

Abstract

A process model for the enzymatic synthesis of (R)-cyanohydrins in an aqueous-organic biphasic-stirred tank reactor was developed. The conversion of benzal-dehyde into (R)-mandelonitrile, catalyzed by Prunus amygdalus hydroxynitrile lyase at 5 degrees C and pH 5.5, was chosen as a model system with methyl tert-butyl ether as the organic phase. The process model consisted of a description of the reaction kinetics, mass transfer kinetics, and the mass balances for both the aqueous and the organic phase. Values for the enzyme kinetic parameters, according to ordered bi-uni kinetics, the lumped mass transfer coefficient for benzaldehyde, and the partition coefficients were determined separately. The process model is validated by using 11 experimental data sets of batch conversions in the aqueous-organic biphasic-stirred tank reactor. In these 11 experiments, different enzyme concentrations and phase volume ratios were used. The model was found to be valid with respect to both the conversion and the enantiomeric excess. To synthesize cyanohydrins with a high enantiomeric excess, the enzyme is required to work at mass transfer limited conditions. The developed process model will be used to investigate other process concepts and other substrates.

Model-based experimental analysis of enzyme kinetics in aqueous–organic biphasic systems

“…The main reason is that mechanistic kinetic modeling assures the correctness of the model prediction if the model is extrapolated (Franceschini and Macchietto, 2008d). Thus, it can be applied for model-based process design, optimization, control, operation, and scale-up of processes without the need to perform a very large range of experiments (Bardow and Marquardt, 2007;Berger et al, 2001;Willeman et al, 2002aWilleman et al, , 2002b. This is especially important for the production of hydrophobic fine chemicals, where a high performance process is essential (Blaser, 2003).…”

“…3-8 k i,org and k i,aq are the mass transfer coefficients within the organic and the aqueous boundary layer. However, this term contains only constants and thus can be combined to one single parameter in order to reduce the number of unknown parameters (Bauer et al, 2002;Mollerup and Hansen, 1998;Willeman et al, 2002aWilleman et al, , 2002b.…”

“…This makes process design more complex (Halling, 1994) and may result in mass transfer limitation which lowers the productivity (Baldascini et al, 2001). However, in certain cases mass transfer limitation can also be favorable, for example in order to suppress a chemical side reaction (Gerrits et al, 2001;Willeman et al, 2002a). Mass transfer limitation can be avoided by decreasing the enzyme concentration or by increasing agitation or interfacial area (Straathof, 2003).…”

Application of modeling and simulation tools for the evaluation of biocatalytic processes: A future perspective

“…When the focus of the model is on reactor design, mass balances are also included to describe/compare various reactor configurations (batch or fed-batch vs. continuous). Moreover, mass transfer limitations are considered particularly when building models for immobilized enzyme systems 29 as well as biphasic systems (e.g., between organic and aqueous phases when organic solvents are used in the biocatalytic process 17,19,31 ). The effects of mixing and hydrodynamics in reactors have typically been neglected by assuming ideally mixed conditions (homogenous concentration throughout the reactor), which were described using the continuously stirred tank reactor (CSTR) concept.…”

Biocatalytic process optimization based on mechanistic modeling of cholic acid oxidation with cofactor regeneration

“…For instance process design optimization and analysis are the common focuses of most studies (Sin et al, 2009). In literature several applications of kinetic models integrating various aspects, for example, toxicity of substrates and enzyme inactivation, are described (Chen et al, 2007;Illanes et al, 1999;Willeman et al, 2002).…”