62 Chapter 4 environment. Cultural influences have also led to preferences for certain food types. In more affluent countries foods such as meat, or high-protein feedstuffs on which to rear animals, can be produced or be imported. In less affluent countries such luxuries cannot be afforded, Increasing populations in some countries have overstretched food d so limited the availability of foods. changing There are problems, however, with these conventional sources of protein. Crop demands for oduction is dependent upon a suitable climate and in most countries available arable land is already fully farmed. Fish stocks in the oceans are in danger of becoming depleted. In countries where animal meat forms a high proportion of dietary protein, there are controversies such as whether or not the fats eaten with the protein are healthy,whether or not we are justified in keeping killing animals for food at all.Such animals in the unnatural conditions controversies are leading an increasin g eople to become vege likely that the worlds population will double in the next few decades, yet the United Nations estimate that about one thousand million people are already suffering protein deficiency. It is estimated that between 1980 and 2000 the annual demand for protein as food for humans will increase from 50x 10 tonnes to 79 x 10 tonnes, and the demand for protein as feed for animals will increase from 44 x 10 tonnes to 108 x 10 tonnes Biotechnology is being applied to the rapid improvement of conventional food sources, both plant and animal, in an effort to meet the increased demand in food. Interest has also been shown in growing micro-organisms source of protein and it developments in this area that we are going to examine here in detail 4. 3 Single cell protein Single cell protein, normally called simply sCP, is the term used to describe microbial cells, or proteins from them, which are used as food ( food for humans)or feed (food for farm animals or fish). Although the term micro-organisms covers viruses, bacteria fungi, algae and protozoa, viruses and protozoa are not considered suitable for sCP production. ∏ Why do you think viruses and protozoa are not suitable for sCP production? Both viruses and protozoa are difficult to grow in culture. Viruses need living cells to grow in and their small size makes them difficult to deal with. Protozoa need complex diets of organic materials. Bacteria, fungi and algae are relatively easy to grow in The term SCP is not exactly appropriate, as some filamentous organisms are used as SCP and these organisms are multicellular not unicellular You may be wondering why anyone should ever have considered using micro-organisms as a protein source. Let us consider why this should have been 4.3.1 The advantage of micro-organisms as a protein source Eating micro-organisms is nothing new. You might not have been aware that some foods traditionally eaten by man are in fact micro-organisms. Filamentous blue-green bacteria(often called blue-green algae, or cyanobacteria) were collected from lakes and rivers and eaten by the Aztecs in Mexico, and people inhabiting the shores of lake Chad in Africa still do so. Edible fungi have been collected from the wild for centuries and yeasts farmed throughout the last two. During the two World Wars this century, yeasts (unicellular fungi)were grown on a large scale in Germany and used as food and feed.62 Chapter 4 changing demands for dietary protein single cell and fwd proteinlfood filamentous blue-green bederia environment. Cultural influences have also led to preferences for certain food types. In more affluent countries foods such as meat, or high-protein feedstuffs on which to rear animals, can be produced or be imported. In less affluent countries such luxuries cannot be afforded, Increasing populations in some countries have overstretched food supplies, and so limited the availability of foods. There are problems, however, with these conventional sources of protein. Crop production is dependent upon a suitable climate and in most countries available arable land is already fully farmed. Fish stocks in the oceans are in danger of becoming depleted. In countries where animal meat forms a high proportion of dietary protein, there are controversies such as whether or not the fats eaten with the protein are healthy, whether or not we are justified in keeping animals in the unnatural conditions of some farms, or whether or not we are justified in killing animals for food at all. Such controversies are leading an increasing number of people to become vegetarian. It is likely that the world’s population will double in the next few decades, yet the United Nations estimate that about one thousand million people are already suffering protein deficiency. It is estimated that between 1980 and 2000 the annual demand for protein as food for humans will increase from 50 x lo6 tonnes to 79 x lo6 tonnes, and the demand for protein as feed for animals will increase from 44 x lo6 tonnes to 108 x lo6 tonnes. Biotechnology is being applied to the rapid improvement of conventional food sources, both plant and animal, in an effort to meet the increased demand in food. Interest has also been shown in growing micro-organisms as a source of protein and it is developments in this area that we are going to examine here in detail. 4.3 Single cell protein Single cell protein, normally called simply s8, is the term used to describe microbial cells, or proteins from them, which are used as food (food for humans) or feed (food for farm animals or fish). Although the term micro-organisms covers viruses, bacteria, fungi, algae and protozoa, viruses and protozoa are not considered suitable for SCP production. n Why do you think viruses and protozoa are not suitable for SCP production? Both viruses and protozoa are difficult to grow in culture. Viruses need living cells to grow in and their small size makes them difficult to deal with. Protozoa need complex diets of organic materials. Bacteria, fungi and algae are relatively easy to grow in culture. The term SCP is not exactly appropriate, as some filamentous organisms are used as SCP and these organisms are multicellular not unicellular. You may be wondering why anyone should ever have considered using micmaganisms as a protein source. Let us consider why this should have been. 4.3.1 The advantage of micro-organisms as a protein source Eating micro-organisms is nothing new. You might not have been aware that some foods traditionally eaten by man are in fact micro-organisms. Filamentous blue-p;reen bacteria (often called blue-green algae, or cyanobacteria) were collected from lakes and rivers and eaten by the Aztecs in Mexico, and people inhabiting the shores of Lake Chad in Africa still do so. Edible fungi have been collected from the wild for centuries and farmed throughout the last two. During the two World Wars this century, yeasts (unicellular fungi) were grown on a large scale in Germany and used as food and feed