Single Cell Protein (SCP): Microbes, Production, Uses

Single Cell Protein is the dried cells of microorganisms consumed as a protein supplement by humans or animals.

The protein is derived from cells of micro-organisms such as yeast, fungi, algae, and bacteria which are grown on various carbon sources for synthesis.

With the increase in population and worldwide nutrient deficiency, the use of microbial biomass as food and feed is highlighted.

SCPs contain vitamins, e.g., thiamine, riboflavin, pyridoxine, nicotinic acid, pantothenic acid, folic acid, biotin, cyanocobalamin, ascorbic acid, β-carotene and α- tocopherol; essential amino acids, represented by lysine and methionine; minerals; nucleic acids and lipids.

The microorganisms used in single-cell protein production should have the following properties.

1. Absence of pathogenicity and toxicity
2. Protein content and quality
3. Digestibility and organoleptic qualities
4. Growth rate
5. Adaptability to unusual environmental conditions such as pH, temperature, and mineral concentrations.
6. Ability to utilize carbon and nitrogen sources.

History of Single Cell Protein (SCP)

• The SCP was first developed during World War I.
• In 1919, Sak in Denmark and Hay duck in Germany invented a method named Zulaufverfahren in which sugar solution was fed to an aerated suspension of yeast instead of adding yeast to the diluted sugar solution.
• Saccharomyces cerevisiae was produced in Germany from molasses to replace protein.
• Candilaarborea and C. utilis were used during the Second World War.
• Similarly, during World War II Candida utilis was used in soup and sausage.
• Many industries were established in the USA and Europe, especially for C. utilis production after the war.
• During the 1960s and 1970s, production industries were established in the UK, France, Italy, Russia, Japan, and Taiwan.
• The term single-cell protein was coined by Carol L. Wilson in 1966.
• In the 1960s, researchers at British Petroleum developed a technology called the proteins-from-oil process for producing
• Initial research work was done by Alfred Champagnatar and BP s Lavera, Oil Refinery in France; a small pilot plant there started operations in March 1963.
• Champagnat was awarded with the UNESCO Science Prize in 1976.
• The Soviets were opening large “BVK” (belkovo-vitaminny kontsentrat, i.e., “protein-vitamin concentrate” plants next to their oil refineries in Kstovo (1973) and Kirishi (1974). 
• The Soviet Ministry of Microbiological Industry had eight plants by 1989 but when the environmentalist movements began to give pressure on the government, they decided to close them down or convert to some other microbiological processes.
• In 1973, a few species of actinomycetes and filamentous fungi were reported for protein production by using various substrates, at Second International Conference which was held at MIT.
• In recent times, among the European Communist countries, Russia has had the greatest capacity for SCP production, with at least 86 plants in operation, using different substrates.

Organisms used as Single Cell Protein (SCP) and the substrate used for their production

Fungi and substrates utilized by them and the protein content produced

Algae and substrates utilized by them and the protein content produced

Bacteria and substrates utilized by them and the protein content produced

Single Cell Protein production method

1. Selection of substrate and strain

• The fast-growing microorganisms are selected that are rich in protein content and possess suitable growth characteristics.
• Then suitable substrates are chosen that are essential for the growth of selected microorganisms.

2. Fermentation

• A fermenter is an instrument, which is set up to carry out the process of fermentation mainly the mass culture of plant or animal cells.
• The inoculated medium is then placed in a fermenter where the microorganisms grow and multiply. The conditions inside the fermenter, such as temperature, pH, and oxygen levels, are carefully controlled to optimize the growth of the microorganisms.

3. Harvesting

• After fermentation, the microbial cells are harvested and separated from the growth medium.
• However, the harvesting and purification after production of SCP production remain a problem.

4. Post-harvest treatment

• The harvested microbial cells are then dried to preserve them and reduce their volume, making them easier to store and transport.

5. SCP processing for food

• The dried cells are then processed to remove impurities, improve their nutritional content, and enhance their flavor and texture.

Advantages of Single Cell Protein

Microorganisms are usually used for the production of SCP because of the following advantages.

1. Microorganisms grow at a faster rate compared to the growth of protein-rich grain which takes a year for production.
2. The quality and quantity of protein are better (60-80%).
3. A wide range of inexpensive raw materials can be used easily.
4. The production process is easy and simple.
5. The microorganisms can be easily subjected to genetic manipulation.
6. The microorganism can be produced all-around a year.
7. They can utilize a wide range of substrates.
8. The production of SCP is eco-friendly, cost-effective, and energy efficient.

Disadvantages of Single Cell Protein

1. The production of SCP is a complex process that requires strict control over various environmental factors.
2. Maintaining the quality of SCP is a hard job as the harvesting and purification after production of SCP production remains a problem.
3. SCP is not a suitable source of all the essential amino acids, so it is typically used as a supplement to other protein sources
4. Despite the many potential benefits of SCP, consumer perception remains a significant challenge, as many people may be skeptical of consuming a product derived from microorganisms.

Applications of Single Cell Protein

• In animal feed and nutrition, for the stuffing and fattening of poultry, laying hens, calves, and pigs.
• As food additives (vitamin and aroma carriers and emulsifying agents), to enhance nutritional value (of baked food items, ready-made meals, soups, etc.), and as starter cultures (baker’s, brewer’s, and wine yeast).
•  In industrial processes, as a foam-stabilizing agent, and in paper and leather processing.
• SCP provides the best protein-supplemented food for undernourished children as it serves as a good source of vitamins, amino acids, minerals, etc. 
• They are used in therapeutic and natural medicines for controlling obesity, lowers the blood sugar level in diabetic patients, reduces body weight, cholesterol, and stress, and prevents the accumulation of cholesterol in the body. 
• SCP is used in Cosmetics products for maintaining healthy hair, production of different herbal beauty products, like- Biolipstics, herbal face cream, etc.

References

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