This book discusses various aspects for consideration while designing a bioreactor with particular emphasis to those reactions that require light, and thus the reaction unit is called PhotoBioReactor. Various designs dominant in the industry are discussed with their pros-and-cons and various limiting reaction conditions are discussed which are important during automation consideration such as by means of a chemostat unit or linked to a Computer unit that has a synchronous deep learning or machine learning module to match up with the growth rate required for the bio-based chemicals of interest or the microbial organism such as algae, cyanobacteria, etc. Please note that the details of machine learning and deep learning algorithms are not discussed in this book as they are fairly straightforward that can be deployed to a Computer unit connected to various sensors for reading pH, dissolved Oxygen, dissolved Carbón Dioxide, etc. The book discusses granted patent application nr: 1135/DEL/2006 and walks through various steps needed with example culture of algae, inoculation, different reagents & equipments needed & the various calculations done to design the bioreactor.