Abstract
Based on experimental data of both batch and continuous enzyme-catalyzed kinetic resolutions of (±)-trans-1,2-cyclohexanediol in supercritical carbon dioxide, kinetic models of increasing complexity were developed to explore the strengths and drawbacks of various modeling approaches. The simplest, first-order model proved to be a good fit for the batch experimental data in regions of high reagent concentrations but failed elsewhere. A more complex system that closely follows the true mechanism was able to fit the full range of experimental data, find constant reaction rate coefficients, and was successfully used to predict the results of the same reaction run continuously in a packed bed reactor. Care must be taken when working with such models, however, to avoid problems of overfitting; a more complex model is not always more accurate. This work may serve as an example for more rigorous reaction modeling and reactor design in the future.
Highlights
The production of single enantiomers has become increasingly important in the pharmaceutical, food, and health industries with a global market share of 39.79 billion USD in 2015.1 achiral organic synthesis followed by diastereomer formation is still the most common resolution method for the preparation of enantiopure substances, biocatalysis provides an alternative opportunity to prepare useful chiral compounds.[2]
Model A was and well regressed against the data. This is not surprising given that its set of ordinary differential equations (ODEs) could be solved symbolically and every species in the model was explicitly measured
Parameter values became conflated and finding a valid global minimum proved impossible; a good fit for the data could be found at a plurality of parameter sets
Summary
The production of single enantiomers has become increasingly important in the pharmaceutical, food, and health industries with a global market share of 39.79 billion USD in 2015.1 achiral organic synthesis followed by diastereomer formation is still the most common resolution method for the preparation of enantiopure substances, biocatalysis provides an alternative opportunity to prepare useful chiral compounds.[2] Enzyme-catalyzed reactions are often highly enantioselective and regioselective. Supercritical carbon dioxide (scCO2) possesses gaslike diffusivity and low viscosity; mass-transfer resistance between the reaction mixture and the active sites of the enzyme is reduced. ScCO2 is nontoxic, nonflammable, inexpensive, and, most importantly from a technological standpoint, can be separated from the reaction mixture.[3] Supercritical carbon dioxide is considered as one of the most promising environmentally benign solvents for reactions, for particle formation, and in separation science. Especially lipases, are well suited to performing stereoselective reactions in scCO2.4−6
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