Whey, a by-product of cheese and curd manufacturing, was once considered as a waste product and indeed, even nowadays, its uncontroled delivery to water effluents constitutes a great environmental problem to solve. However, along the chapters of this review book we can follow the change in perception of whey from waste to co-product thanks to the many clever usages of this resource that have been developed in recent years. In the first chapter the discovery and importance of whey or manufactured derivatives as functional foods or alimentary additives is revised thoroughly in relation to the particular functions of its biological components and their effects on diverse disease treatments. Other application of great relevance is considered in chapter two, the production of biofuels, specifically biogas, from cheese whey. The reader will find a summary of how knowledge in the field of biogas production from cheese whey effluents has evolved, the current status quo, and identify areas that should be addressed in the near future. Biosurfactants have many potential applications including enhanced oil recovery, crude oil drilling lubricants, surfactant-aided bioremediation of water-insoluble pollutants, and in the health care and food processing industries. Other developing areas of biosurfactant use are in cosmetic and soap formulations, foods, and dermal as well as transdermal drug delivery systems. The limit to biosurfactant production is usually high cost associated to their production and extraction. Therefore the use of cheese whey as a cheaper substrate opens new areas of research and innovation in this industry as reported in chapter three of this book. Microbial biosynthesis allows the production of optically pure lactic acid, which is highly demanded for several industrial applications. Production of lactic acid by fermentation of lactic acid bacteria on whey has been investigated as a feasible route for processing and upgrading of this effluent. Chapter four summarises the most recent attempts on the utilization of cheese whey as culture medium for microbial biosynthesis of lactic acid, both using free and immobilized microorganisms. Several bacteria are able to produce polyesters as reserve materials of carbon and energy. These polyesters are quite diverse and represent a family of polymers named polyhydroxyalkanotes (PHA). Since mechanical and physical properties of polymers are strongly dependent of monomer composition, it is believed that PHA will constitute tailor made polymers for different applications and therefore have attracted great academic and industrial interest as natural biodegradable thermoplastic and elastomeric materials which could be synthesized from renewable materials. To be competitive with common plastics, the production costs of PHA have to be reduced and in chapter five the use of cheese whey as a cheap carbon source is considered. Single cell protein (SCP) production has been the subject of extensive research mainly for the production of animal feeds enriched in protein by microbial treatment of various agro-industrial wastes in submerged and solid-state fermentation processes. Some physicochemical properties of cheese whey, including high salinity, do not allow easy microbial utilisation. The review on chapter six summarizes recent research attempts trying to deal with the problem and focusing on the development of new technologies and selection or development of microorganisms suitable for maximal yield. Bacteriocins are innocuous peptides, sensitive to digestive proteases and they do not produce changes in the organoleptic properties of the foods. For all these reasons, they have proved to be effective food bio-preservatives. Chapter seven gives several examples of bacteriocins produced in whey-based media and particularly it focuses on Nisin and Pediocin production. The last chapter is devoted to the production of heterologous proteins from whey, a poorly explored field that could greatly improve the cost-effectiveness of whey recycling. Growth of engineered microorganisms in whey is a potential source to produce valuable homologous and heterologous proteins. Scientists are reconsidering the value of various components of milk, including whey, and how they may impact economics aspects of different industrial productions. Considerable positive research regarding whey and its biological components continue to be published and attracting the interest of dairy organizations and public administrations. We expect that this book will contribute to increase the knowledge about this subject and justify the convenience of founding research in this field.

As the number of dairy farms is increasing, it is obvious that the discharge of whey from them can affect the environment. In other hands with this current population explosion and the limited land resources, the world will be soon unable to feed its population. That means protein gap also would continue to increase unless well planned measures are adopted to handle the situation. It is therefore, important to increase protein production by utilizing all the available ways and means. In order to bridge this gap, Single Cell Protein production is an innovative and an alternative way. Thus, this microbial biomass production and bioconversion of the wastes through microbial degradation and is the natural way to recover resources. As far as Single Cell Protein production is concerned, yeasts are probably the most widely accepted. Therefore this work delivers the information about yeast species which can be found in dairy products, their potential in converting substrate lactose to Single Cell Protein and their identification system. Therefore the researchers who have an interest in this area, the food processing industries and the environmentalists can be benefited from this work.

In early 1973, I returned to Israel from a post-doctoral fellowship at Harvard University, and was accepted as a lecturer in the Department of Applied Microbiology at the Hebrew University of Jerusalem. Shortly after my return, Professor Richard Mateles, who at that time was head of the Department, suggested that I purchase a good and comprehensive book on single cell protein (SCP) in order to expand my general knowledge in the subject I had started then to work on; that was microbial utilization of one-carbon (C ) compounds. l Naturally, I took his advice (after all, he was the Boss) and bought the book, which was the only general book published on this subject at that time, and was based on papers presented at the First International Conference on Single Cell Protein, held at the Massachussetts Institute of Technology (M.I.T.), on October 1967 (Mateles and Tannenbaum, editors) [1]. Through this book I became acquainted with the world's hunger problem that existed in the past, and ways in which it was to be solved by SCP products prepared from CO , fossil-based raw 2 materials, and from wastes.