The European Federation of Biotechnology defines biotechnology as ‘the integration of natural sciences and engineering sciences in order to achieve the application of organisms, cells, parts thereof and molecular analogues for products and services’. Biotechnology thus focuses on the industrial exploitation of biological systems and is based on their unique expertise in specific molecular recognition and catalysis. The enormous potential for drug synthesis, design of biomedical diagnostics, large-scale production of biochemicals including fuels, food production, degradation of resistant wastes and extraction of raw materials will very likely make biotechnology, along with electronics and material sciences, one of the key technologies of the 21st century. From the chemical engineer's point of view, the living system participating in a biotechnological process is the central unit that catalyses chemical reactions. It exhibits a complex dependence on the bioprocess parameters, and the engineer focuses on these parameters to achieve optimal control (Hamer, 1985; Bailey & Ollis, 1986). For the natural scientist, the living system itself is in the centre of interest, so that attempts to optimize a bioprocess aim at its appropriate redesign by genetic manipulations. The increase in penicillin production by strain improvement based on random mutagenesis, which was pursued from 1940 to the mid 1970s, represents an early contribution of life scientists to improve a bioprocess that is of utmost medical importance (Hardy & Oliver, 1985).