Whole-cell based biocatalysis provides a great potential for the sustainable production of compounds for the chemical and pharmaceutical industries. Especially in the field of redox cofactor dependent oxygenases, catalyzing the functionalization of carbon-hydrogen bonds, cellular functionalities offer great benefits such as redox cofactor and enzyme regeneration and the handling of reactive oxygen species. However, the interference of recombinant gene expression and enzyme activity with host cell metabolism can lead to hampered cell maintenance and growth physiology and thus affect biocatalyst and process stability. This thesis followed a reaction engineering approach to overcome such stability issues.