Activation of mandelate racemase via immobilization in lyotropic liquid crystals for biocatalysis in organic solvents: application and modeling

Mandelate racemase from Pseudomonas putida ATCC 12633 could be activated in an organic solvent by immobilization in lyotropic liquid crystals (LC). A theoretical model for a system, that consisted of an organic solvent phase to solve the nonpolar substrate and the LC phase with the immobilized enzym e was developed. The model included the biocatalytic reaction and the mass transfer in-between and within the phases. By means of the finite element m ethod (FEM) this model was transferred into a computer program, which was u sed as a tool for the simulation of the racemization Of D-mandelic acid by mandelate racemase in the organic solvent (di-n-butyl ether). The experimen tal results at temperatures ranging from 20 to 60 degreesC and starting con centrations Of D-mandelic acid between 40 and 80 mmol 1(-1) in the organic solvent phase could be simulated by the model with high accuracy. Furthermo re, the model was used to vary the geometry of the system to minimize mass transfer limitations, which represent a crucial limitation for this system. (C) 2001 Elsevier Science B.V. All rights reserved.