ter 4 Single cell protein 4. 1 Introduction In this chapter we examine the processes that have been developed to produce micro-organisms as a source of food protein. We will examine the reasons why micro-organisms have been considered as alternative protein sources, the substrates on which they have been grown, the various process technologies developed and the comparative economics of these processes. One process will be mined in depth, to illustrate how a team composed of such diverse people as microbiologists, process engineers, patent lawyers and cost analysts work together to develop a marketable product The driving forces behind the development of many single cell protein projects emerged from global e conditions and social concerns of the 1960s. In the 1970s and early 1980s, there were considerable technological advancements associated with single cell rotein process developments and many types of prc ocesses were operated commercially. In this chapter we present technological and economic data derived from and animal feed source. You will see that many important principles underpinning modern process technology are based on the experiences gained in the development of single cell protein processes 4.2 Conventional protein sources essential Animals, including humans, cannot synthesise all the different amino acids they need amino aads and thus require them in their diet. These amino acids are called the essential amino acids. Proteins in food are hydrolysed in the digestive tract and the resulting amino acids are reassembled into proteins within the animals cells. All animals are ultimately dependent on plants for protein, as it is plants that create protein by combining inorganic nitrogen from the soil(as nitrate)with organic molecules derived from carbon from the atmosphere(as CO2) organoleptic For us to remain perfectly healthy the protein in our diet must supply suffidient ropertes quantities of amino acids. We prefer to eat our protein in particular forms, that is in foods having particular textures, tastes and smells(these are called organoleptic properties). Conventional sources of protein are plants, mainly as cereals and pulses, and animals, mainly as meat, eggs and milk. The proportions of such proteins eaten in various parts of the world differ widely(Figure 4.1)60 Chapter 4 Single cell protein 4.1 Introduction In this chapter we examine the processes that have been developed to produce micro-organisms as a source of food protein. We will examine the reasons why micmrganisms have been considered as alternative protein sources, the substrates on which they have been grown, the various process technologies developed and the comparative economics of these processes. One process will be examined in depth, to illustrate how a team composed of such diverse people as microbiologists, process engineers, patent lawyers and cost analysts work together to develop a marketable product. The driving forces behind the development of many single cell protein projects emerged from global economic conditions and social concerns of the 1960s. In the 1970s and early 198Os, there were considerable technological advancements associated with single cell protein process developments and many types of processes were operated commercially. In this chapter we present technological and economic data derived from these early developments to provide a historical context for single cell protein as a food and animal feed source. You will see that many important principles underpinning modem process technology are based on the experiences gained in the development of single cell protein processes. 4.2 Conventional protein sources essential aminoacids Animals, including humans, cannot synthesise all the different amino acids they need and thus require them in their diet. These amino acids are called the essential amino acids. Proteins in food are hydrolysed in the digestive tract and the resulting amino acids are reassembled into proteins within the animal's cells. All animals are ultimately dependent on plants for protein, as it is plants that create protein by combining inorganic nitmen from the soil (as nitrate) with organic molecules derived from carbon from the atmosphere (as COJ. For us to remain perfectly healthy, the protein in our diet must supply suffiaent quantities of amino acids. We prefer to eat our protein in particular forms, that is in foods having particular textures, tastes and smells (these are called organoleptic properties). Conventional sources of protein are plants, mainly as cereals and pulses, and animals, mainly as meat, eggs and milk. The proportions of such proteins eaten in various parts of the world differ widely (Figure 4.1). organoleqtic PmeS