This work aims to emphasize the importance of scale-up in biotechnological research, in order to introduce more environmentally friendly bio-catalyzed processes to the industry. Here, a complex biotechnological reference reaction system is investigated, and, for the first time, a successful synthesis of cinnamyl cinnamate from cinnamyl aldehyde in a multiphase system is established. A multi-enzymatic cascade reaction sequence with integrated co factor regeneration and in situ intermediate separation is applied. This highly integrated reaction system is successfully implemented in a pilot-scale reactor plant. Experimental results show complex relationships between physically separated unit operations.