The catalytic activity of oxygenase-based whole-cell biocatalysts is heavily influenced by substrate and product toxicities due to cell membrane permeabilization and protein denaturation effects of the organic substrates and products. Therefore, stability of oxygenase-based whole-cell biocatalysts against solvent stress was investigated with recombinant $Escherichia$ $coli$ BL21 and $Corynebacterium$ $glutamicum$ ATCC13032 expressing the $chnB$ gene of cyclohexanone monooxygenase of $Acinetobacter$ $calcoaceticus$ NCIMB 9871. The cyclohexanone oxygenation activity of the recombinant biocatalysts rapidly decreased as cyclohexanone concentration increased from 2.4 to 26 g/L. However, treatment of the recombinant cells with non-lethal doses of cyclohexanone or preadaptation to the toxic substrate led to the oxygenation activity being relatively maintained. For instance, the oxygenation activity of cyclohexanone-treated $E.$ $coli$ cells was ca. 13 U per g dry cells at the substrate concentration of 26 g/L, which was almost 5-fold higher than that of the cyclohexanone-nontreated cells. In addition, biocatalytic activity was better maintained when the genes encoding chaperones (i.e., GroEL-ES and DnaKJ-GrpE) were coexpressed with the $chnB$ gene. The positive effects of chaperones on the catalytic activity of the recombinant $E.$ $coli$-based biocatalyst appeared to be related with expression level of biotransformation enzymes rather than with solvent stress-response metabolism. Overall, molecular chaperones, of which expression can be induced by solvent treatment, were involved in catalytic stability of whole-cell biocatalysts during biotransformations involving toxic compounds as the reactants.