Single cell proteins are dried cells of microorganisms that can be used as a dietary protein supplement for humans and animals. They are produced by growing microorganisms like yeast, algae, fungi and bacteria on various substrates. The microorganisms are harvested and processed to extract protein. Single cell proteins have high protein content and offer a sustainable source of nutrition but their production requires sterile conditions and the protein extract may cause allergic reactions in some people.

1. What Are Single Cell Protein
• Single Cell Proteins are dried cells
of micro organisms which can be
used as dietary protein supplement.
• They are used as animal feed &
can be used for human feed as
protein supplement.
• Also called ‘Novel Food’ &
‘Minifood’.

2. Single Cell Protein/ Microbial Protein
• The term “Single Cell Protein” refers to the total protein extracted from the pure
cultures of microorganisms (e.g. yeast, algae, filamentous fungi, bacteria) and
can be used as a protein-rich food supplements by humans and animals.
• Also known as ”Microbial Protein”

3. History
• Part of our diet since ancient times.
• Earlier known as ‘Microbial Protein’.
• Transportation of food was common in the past but with the increase in population, energy crisis
has encounter the world.
• So there should an alternate food/protein source to overcome this energy crisis.
• In 1950’s British Petroleum initiated production of SCP on commercial basis.
• In 60s’, idea that the dried cells of micro- organisms can become an ultimate part to solve this
problem. Thus gained research interest among the scientists & industries (specifically oil industry)
• 1966: Professor Carroll L.Wilson renamed it as “Single Cell Proteins”

4. History
• Pruteen was the 1st commercial SCP used as animal feed additive
• Pruteen was produced from bacteria Methylophilus methylotrophus cultured on methanol & had 72
% protein content.
• In 1960s,researchers at british petroleum developed what they called “proteins from oil process”;a
technology for producing SCP by yeast fed by waxy-n-paraffins,a product produced by oil
refineries.
• The “food from oil” idea became quite popular by the 1970s,with the champagnat being awarded
the UNESCO science prize in 1976,and paraffin fed yeast facilities being built in a no.of countries.
• SCP contains fats,carbohydrates,vitamins,nucleic acid,&minerals.
• SCP rich in certain essential amino acids(lysine,methionin).

5. Production of SCP
Large scale processes for SCP production show interesting features including:
• The wide variety of methodologies, raw materials, and microorganisms that can be used for this
purpose.
• High efficiency in substrate conversion.
• High productivity, derived from the fast growth rate of microbes.
• Independence of seasonal factors.

6. Production of SCP
Raw Materials
• Production of SCP requires micro-organisms that serve as the protein source and the
substrate that is biomass on which they grow.
• There is a variety of both the sources that can be used for the production of SCP.
• The biomass used can be plant biomass or organic biomass.
Biomass
• Biomass also plays a very important role in the production of SCP.
• Selection of biomass depends on the micro-organisms used for the production.
• For example, Algae are cultivated on sewage whereas Yeast are cultured on agro-
industrial wastes.

7. Steps of SCP Production
Production of SCP involves following steps:
• 1. Selection of Strain of microbe and Substrate
• 2. Fermentation
• 3. Harvesting
• 4. Post harvest treatment
• 5. Processing of SCP

8. 1.Selection of Microbial Strains and Substrates
• Very Crucial step.
• Microbe selected shouldn’t produce toxicity in its biomass.
• It should not be harmful for a consumer to consume.
• Selected microbe should produce a large quantity of protein.
• Substrate should be cheap, effective, allow favorable growth and ease of
isolation.

9. Micro-organisms used for production of SCPs
• Micro-organisms that can be used for the production of SCPs are:
• 1. Filamentous Fungi
• 2. Yeast
• 3. Algae
• 4. Bacteria

10. YEAST
• In the World War 1st, one of its specie Candida utilis (Torula yeast)
was produce by Germany and used in soups and sausages.
• It is also used commercially as seasoning of food and one of the
examples of this is “Hickory Smoked Dried Torula Yeast”.
• The Baker’s yeast (Sacchromyces cerevisiae) is used commercially in
food bakeries.
• Suitable substrate e.g. molasses, corn- steep liquor etc.
•
• Controlled conditions (temp. 25-26C, aeration, pH 4-4.4, C-source, S-
source, and N-source).

11. YEAST
Yeast has some advantages among other SCP sources e.g.
• The biomass can easily be harvest because of the larger size of yeast as compare too many
bacteria.
• Yeast has long traditional history of its use.
• Biomass produce contain high levels of lysine & malic acid.
• It can grow at highly acidic pH.
Whereas, there are some disadvantages too which includes:
• Yeast has lower growth rate as compare to bacteria.
• Low overall protein contents (45-65%)

12. Filamentous Fungi
• In 1973, Actinomycetes & some other filamentous fungi were found to produce SCPs.
• Require optimum temp. 25-30C, pH 5-6 or below, ammonium salt as N-source.
Advantages of fungi to be used as a SCP producer are:
• 1. Faster growth
• 2. High protein contents
• 3. Higher penetration power into substrate
Disadvantages include:
• 1. Some fungi show slower growth
• 2. Produce mycotoxins
• 3. Risk of contamination

13. Algae
Many algal sp. are being used for mass cultivation e.g.
• Chorella,
• Spirulina etc.
Advantages are
• Protein-rich.
• simple and fast growth.
• Require no CO2 aeration but require temp.25C & pH 8-10.
• Low overall protein contents (45-65%).

14. Bacteria
• Growth requires pH 5-7 and temperature 35-45C.
Advantages of bacterial strains producing SCPs are:
• Rapid growth
• Short generation time of about 2- 20minutes
• Utilization of any kind of raw material as a C-source

17. 2. Fermentation
• Is done in a large chamber either of glass or
stainless steel called “Fermentor”.
• Fermentation should be done under sterilized
conditions.
• Controlled conditions as necessary e.g.
Temperature, Pressure, pH, Humidity etc.
• Usually fed-batch cultures are used for the
fermentation of microbes.

18. 3. Harvesting
• Fermentation yields a lager number of microbial colonies produced from single cell.
• These colonies are isolated from individual cell by the method of “Decantation”.

19. 4. Post harvest treatment
• Isolated microbial colonies are subjected to various differential techniques.
• E.g. Centrifugation,
• Washing,
• Drying etc

20. 5. Processing of SCP
• Produced protein contain impurities in it e.g. carbohydrates, nucleic acids,
lipid contents, salts etc.
• Pure protein isolation can be done by disrupting the cell wall through
crushing, crumbling, cycles of freezing & thawing, grinding & thermal
shocks.
• Nucleic acid can be remove by: 1. By treatment with Nacl 10% 2. By
Chemicals e.g. NaoH 3. Thermal shocks 4. Enzymes Treatment e.g.
ribonucleases

21. Advantages of SCPs
Some of the advantages of SCPs are as followed:
• Microbes have rapid succession of generation thus number of generation can be obtained in a very
short interval of time(algae 2-6 hrs, yeast 1- 3hrs, bacteria 0.5-2hrs)
• They can easily be modified genetically for varying the amino acid composition.
• They contain 43-85% of protein contents in their dry mass.
• Microbes can use a variety of raw materials as their source of carbon and thus can cause the
removal of pollutants from the environment.
• High yield and good composition SCP
• Can be produce and isolated easily.
• It is beneficial ecologically

22. Disadvantages of SCPs
The disadvantages of SCPs are mentioned below:
• Some microbes are harmful for both humans and animals and can produce toxins
in their biomass which may cause diseases in humans and animals.
• Microbial biomass may lead to some allergic reactions and indigestion.
• The higher nucleic acid contents in SCPs may lead to human kidney stone.
• Production of SCPs is very expensive method and requires highly sterilized
conditions.
• Taste may change & some unacceptable coloration may produce.

23. Application of SCP
• Act as a Food source e.g. aroma carriers, vitamins carriers, emulsifying acids, in soups,
in ready-to-serve food items etc.
• In technologies e.g. paper industry, leather processing & foam stabilizers.
• Used in poultry & animal feed industry.
• Have medicinal uses.

24. Conclusion
The development of Single Cell Protein is just a beginning in biotechnology.
With the improvement in the production of SCPs, we can solve the malnutritive conditions
of the progressing countries and can also introduce better quality of food and taste with
decreased chances of occurrence of side effects.
Moreover, genetic modification in microorganisms can lead to a better future of SCPs in
biotechnology, medicines, agriculture, poultry etc.