Protein single cell

The biomass formed during a fermentation is a source of high-quality protein and vitamins. For this reason Clostridium acetobutylicum was once used to supplement animal feeds (see section 6.2.1.2), and Saccharomyces cerevisiae from the ethanol fermentation now finds a similar use in the United States. Where the value of the fermented biomass has made it attractive as a product in its own right, it is the sheer scale of the process which is important for industrial chemistry. 

The continuous fermentation is different in principle from the traditional batch processes of the fermentation industry. It has several advantages, not least of which is that one fermenter can supply a constant stream of broth for the protein recovery processes. The recovery plant is therefore on a smaller scale than would be required for the batch processing of all lOOOm of broth. 

In the UK and the USA the product no longer really justifies itself as an animal feed. The set of conditions in which cheap methane could, through synthetic methanol, be economically converted to protein have now been replaced by others in which carbohydrates from agriculture are economic sources of ethanol, a fuel which directly rivals methanol. The value of the product might be upgraded if it were treated as a raw material from which a number of biological materials might be manufactured, and small-scale processes do exist for a few compounds which could be recovered from the cells. However, other constraints apply in the USSR where about 10 M tonnes of bacterial protein are produced each year from a variety of hydrocarbon feedstocks.  

Continuous fermentation for microbial products apart from protein has not achieved the success of a batch process, because the yields in the latter are higher. However some of the large-scale techniques will undoubtedly influence the design of future fermentation plants, and there is no reason why this influence should not extend to some of the traditional batch processes. 

The protein content of bacteria is higher than that of yeasts and contains higher concentrations of the sulphur-containing amino acids but a lower concentration of lysine. Single-cell protein (SCP) contains unusually high levels of nucleic acids, ranging from 50 g/kg DM to 120 g/kg DM in yeasts and from 80 g/kg DM to 160 g/kg DM 

Substrates used Microorganism DM (g/kg) Organic matter Crude protein Crude fat Crude fibre Ash 

After Schulz E and Oslage H J 976 Animal Feed Science and Technology 9. 

In the case of poultry, dietary SCP concentrations of 20-50 kg/t have proved optimal for broilers, and 100 kg/t has been suggested for diets for laying hens. 

---

Single-Cell Protein. Systems involving single-cell proteins are often very large throughput, continuous processing operations such as the Pmteen process developed by ICI. These are ideal for air-lift bioreactors of which the pressure cycle fermenter is a special case (50). 

The Protein Advisory Group, ad hoc, is the working group of the WHO United Nations system involving WHO, EAO, and the United Nations International Childten s Emergency Eund (UNICEE). It has developed guidelines for the evaluation of novel sources of protein, eg, single-cell protein ... 

In general, nonconventional protein foods must be competitive with conventional plant and animal protein sources on the bases of cost delivered to the consumer, nutritional value to humans or animals, functional value in foods, sensory quality, and social and cultural acceptability. Also, requirements of regulatory agencies in different countries for freedom from toxins or toxic residues in single-cell protein products, toxic glycosides in leaf protein products, pathogenic microorganisms, heavy metals and toxins in fish protein concentrates, or inhibitory or toxic peptide components in synthetic peptides must be met before new nonconventional food or feed protein products can be marketed. 

S. Bernstein, G. H. Tzeng, and D. Sisson in A. E. Humphrey and E. L. Gaden, Jr., eds., Single-Cell Protein from Renewable andNonrenewable Resources, John Wiley Sons, Inc., New York, 1977, pp. 35—44. 

Future Uses. The most recent uses for methanol can be found in the agricultural sector. Test studies are being carried out where methanol is sprayed directly onto crops to improve plant growth. Methanol can be used as a carbon source for the production of single-cell protein (SCP) for use as an animal feed supplement. The process has been commercially demonstrated by ICl at their BiUingham, U.K., faciUty. However, the production of SCP is not commercially practical at this time, in comparison to more conventional protein sources. 

Loop reactors are particularly suitable as bioreactors to produce, for example, single-cell protein (96). In this process, single yeast or bacteria ceUs feeding on methanol multiply in aqueous culture broths to form high value biomass at 35—40°C, 20 kg/m ceU concentrations, and specific growth rates of... 

Sulfite waste Hquor from the pulping industry contains a large amount of hydrolyzed sugars. Some sulfite waste Hquors are now being fermented to give both ethanol (qv) and single-cell protein in the form of yeast (see Foods, non-CONVENTIONAL Yeasts). 

Single-cell protein production Organic waste... 

Single cell protein Cells, or protein extracts, of microorganisms grown in large quantities for use as human or animal protein supplements. 

Normal paraffins in this range are important intermediates for alkylating benzene for synthetic detergents production (Chapter 10). They are also good feedstocks for single-cell protein (SCP). 

FERMENTATION USING n-PARAEEINS (Single Cell Protein SCP)... 

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. 

---