?Prof. Dr.-Ing. Ralf Pörtner: Senior research associate and group leader at Hamburg University of Technology, Institute of Bioprocess and Biosystems Engineering and Honorary Professor at TH Mittelhessen University of Applied Sciences, Giessen. The main research interests of Prof. Pörtner are development and optimization of bioreactor techniques and process strategies, in particular for cell cultures and microbial reactions, including model-based control concepts, and tissue engineering. He has in total published about 150 peer-reviewed papers.