This book reviews the potential of mixed microbial cultures in industrial bioprocesses, offering groundbreaking insights and practical applications. It addresses different applications and challenges and discusses potential solutions for utilizing mixed cultures. Through this book, readers will learn about the latest advancements in microbial bioprocessing, from innovative fermentation techniques to sustainable waste management solutions. Divided into 10 chapters, the book covers topics such as mixed strain fermentation and metabolomics, and the dynamic nature of the human gut microbiota. Expert contributors also explore critical issues like selenium removal from wastewater, simultaneous CO2 absorption and wastewater treatment, and the production of novel energy gases using undefined mixed cultures. This book highlights the power and benefits of microbial communities and their metabolic networks by describing how they can be harnessed for food and forest industry waste reuse and the upgrading of products from bio-refinery pilots. The combinations of economically feasible and sustainable processes in ecosystem engineering are also discussed. Finally, the future of biorefinery industries as a part of circulation economies and healthier environments is discussed. Given its breadth, the book is a valuable resource for researchers in biochemical engineering and biotechnology fields, as well as anyone dealing with industrial R&D, construction projects or sustainable food and feed production. The empirical research and its outcomes presented here address pressing environmental challenges, making this volume a must-read for anyone committed to advancing sustainable biotechnological solutions.