This book comprises a total of fourteen chapters contributed by experts from different countries across the globe. The book is divided into five sections containing two to three chapters each. It is a comprehensive collection of articles that give an overview of microbial catalysts which include enzymes that contribute to many fields and are widely used in industrial products. Microorganisms have served and continue to serve as one of the largest and useful sources of many enzymes used in foods and the food industry. Microbial catalysts are environmentally friendly and consume lower energy. A particular focus of this book is on applied and industrial microbiology, agricultural microbiology, and food microbiology. All of the sections discuss microbial catalysts, enzymes with respect to their function and their benefits to humankind in general, and biotechnology as a subject of which enzymology is an integral part. This book deals also with the structure and function of some microbial enzymes. Microbial catalysts are generally preferred than plants and animals as sources of industrial enzymes because their production cost is low. In addition, their enzyme content is more predictable and controllable, and more so because of the easy availability of raw materials with constant composition for their cultivation.