Kinetic modeling of a crude DERA lysate-catalyzed process in synthesis of statin intermediates

摘要

The kinetics of enzymatic aldol reaction catalyzed by DERA (2-deoxyribose-5-phosphate aldolase) was studied. The reaction between acetyloxyacetaldehyde/acetaldehyde and chloroacetaldehyde/acetalde-hyde in the presence of DERA produces chiral lactol intermediates, which are useful in the synthesis of optically pure super-statins. The experimental approach was designed studying batch and fed-batch reaction conditions adding different amounts of applied reactants. A three-step kinetic model was proposed including the formation of the intermediate product, synthesis of the main desired product and the synthesis of the side product by parallel non-desired secondary reaction. The kinetics of enzyme inac-tivation caused by reactants was also included in kinetic model design. The establishment of the kinetic model based on the two-substrates binding assuming random mechanism. After the development of the kinetic model, kinetic parameters were determined by non-linear least squares approximation search method, until the minimal differences between experimental and calculated data were achieved. The highest concentrations of the desired main product were produced in the case of fed-batch experiments applying such feeding regime that minimal surplus of reactants in the reaction mixture was attained, which consequently led to lower losses in the enzyme activity. Obtained kinetic parameters showed similar value of inactivation constant for acetyloxyacetaldehyde and acetaldehyde, whereas in the case of chloroacetaldehyde the number was significantly higher. To our knowledge, this is the first developed kinetic model describing the DERA catalyzed reaction of 2-substituted acetaldehydes to corresponding lactols. Obtained kinetic model can be used in further reactor design in the manner of optimizing the process by lowering the loss of enzyme activity in order to achieve higher amounts of the desired main product.