Cascade Synthesis from Cyclohexane to ϵ-Caprolactone by Visible-Light-Driven Photocatalysis Combined with Whole-Cell Biological Oxidation

Graphical Photoenzymatic combinations : Cyclohexane was oxy-functionalised to ϵ -caprolactone directly through a cascade reaction sequence combining visible-light-driven photocatalysis with whole-cell biocatalysis. Two photocatalysts, Au-doped TiO 2 and graphitic carbonitride, were used in the reaction. After expression of cyclohexanone monooxygenase (CHMO) in E. coli , the whole cells were used as biocatalyst. Cyclohexane was directly oxy-functionalised to ϵ-caprolactone through a cascade reaction sequence combining visible-light-driven photocatalysis with cyclohexanone monooxygenase (CHMO) whole-cell biocatalysis. Two available photocatalysts, Au-doped TiO 2 (Au-TiO 2 ) and graphitic carbonitride (g-C 3 N 4 ), were evaluated in the experiment and some optimisations to the cascade reaction were applied. In stepwise mode, the highest degree of conversion from cyclohexanol to ϵ-caprolactone can be up to 41 %, with use of g-C 3 N 4 . The cascade reaction from cyclohexane to ϵ-caprolactone is achievable under a light intensity of 149 μW cm −2 .