In the book, contemporary approach for monitoring and control of biotechnological processes on new formalization of process kinetics is presented. The new idea is the substrate kinetics to be considered as fully unknown and time-varying. This new formalization allows avoiding widespread conception for bioprocess models with constant yield coefficients. In practice, the model coefficients of such processes with nonlinear nature and low level of reproducibility are time-varying. Different applications and modifications of the proposed approach are presented. The modifications ensue from the process characteristics – process target product and available information. The present book generalizes the long authors'' experience with different bioprocesses in food and pharmaceutical industries, in wastewater treatment as well as for bio-fuels production from renewable sources. It is intended as a graduate level text for students in bioengineering as well as a reference text for scientists and engineers involved in bioprocess control design.