Permeabilized Escherichia coli Whole Cells Containing Co-Expressed Two Thermophilic Enzymes Facilitate the Synthesis of scyllo-Inositol from myo-Inositol

Scyllo-inositol (SI), a stereoisomer of inositol, is regarded as a promising therapeutic agent for Alzheimer's disease. Here, an in vitro cofactor-balance biotransformation for the production of SI from myo-inositol (MI) by thermophilic myo-inositol 2-dehydrogenase (IDH) and scyllo-inositol 2-dehydrogenase (SIDH) is presented. These two enzymes (i.e., IDH and SIDH from Geobacillus kaustophilus) are co-expressed in Escherichia coli BL21(DE3), and E. coli cells containing the two enzymes are permeabilized by heat treatment as whole-cell catalysts to convert MI to SI. After condition optimizations about permeabilized temperature, reaction temperature, and initial MI concentration, about 82 g L^-1 of SI is produced from 250 g L^-1 of MI within 24 h without any cofactor supplementation. This final titer of SI produced is the highest to the authors' limited knowledge. This study provides a promising method for the large-scale industrial production of SI.