This chapter discusses three reaction systems, including bubble column reactor (BCR), lab-scale stirred-tank and fixed-bed reactor. It demonstrates the application of BCRs for the synthesis of high-viscous cosmetic esters. The majority of cosmetic esters are produced chemically in various reactor types. The most important key figures that characterize a BCR for biocatalytic reactions are hydrodynamics, gas content, mass transport, heat transfer and gas or phase distribution. The chapter shows the application of a BCR as an alternative reactor concept for processing high-viscous reactants. It also demonstrates online monitoring of fatty acid conversion as well as determination of water concentration by means of attenuated total reflection Fourier transform mid-infrared (ATR FT-IR) spectroscopy. Online reaction course monitoring of polyglycerol-3-laurate synthesis is more challenging in view of applying precise analytics compared to the myristyl myristate system. In addition, the synthesis of myristyl myristate was characterized in lab scale as well as pilot scale BCRs.
