Single Cell Protein is defined as crude, refined or edible protein extracted from pure microbial cultures, dead or dried cell biomass. The increase in the world’s population will be a significant challenge to create a sustainable life for humankind. The deficiency of protein may become a primary concern of humans, and it may not be possible for conventional agricultural practices to provide a sufficient supply of food, especially protein.

New agricultural practices are being developed to produce high-protein cereals. New alternate and unconventional proteins obtained from microbial sources like yeast, fungi, bacteria, and algae are named Single Cell Protein. Single Cell Proteins are also known as Novel food, Mini food or Microbial Protein. In this article, we will provide detailed information on Single Cell Protein, its definition, production, etc. Continue reading to learn more about SCP!

Single Cell Protein: Overview

Production of protein biomass on a large scale using microorganisms and growing them in the low-cost raw material is called single-cell proteins. They can be used as a food source or supplement. The term SCP was coined by Carol L Wilson in \(1966\) at the Massachusetts Institute of Technology –USA. Single-cell protein is derived from the cell culture of microorganisms. It refers to the crude or refined protein of algae, bacteria, fungi, or yeast and is used as food or supplement by animals or humans. The microbial biomass is an alternative source for proteins due to its high content of protein. In addition to proteins, SCP also contains other nutrients, such as lipids and vitamins. Single Cell Proteins are also known as Novel food, Mini food or Microbial Protein.

Single Cell Protein: Examples

Some of the microorganisms used in the production of SCP are listed below:

i) Fungi: Yeast (Candida utilis), Fusarium graminearum, Mushrooms like Agaricus campestris and Morchella crassipes. Many people eat mushrooms, and large scale mushroom culture is a growing industry that makes it believable that microbes would become acceptable as food. Fusarium graminearum is used for the commercial production of SCP.

ii) Cyanobacteria: Spirulina can be grown quickly on materials like wastewater from potato processing plants (containing starch), straw, molasses, animal manure and even sewage to produce large quantities and can serve as food rich in nutrients. Incidentally, such utilization also reduces environmental pollution.

iii) Bacteria: Methylophilus methylotrophus bacteria, because of their high rate of biomass production and growth, can produce about \(25\) tonnes of protein per day.

iv) Algae: Chlorella sp., Scendesmus sp., etc.

v) Yeast: Candida sp., Saccharomyces sp., etc.

vi) Actinomycetes: Theromonospora fusca

Fig: Spirulina

Fig: Chlorella

Below we have provided the average composition of various microorganisms present in percentage dry weight of single-cell protein:

Composition	Algae	Bacteria	Fungi	Yeast
Protein	40-60	50-65	30-45	45-55
Fat	7-20	1-3	2-8	2-6
Ash	8-10	3-7	9-14	5-10
Nucleic Acid	3-8	8-12	7-10	6-12

What is the Production of Single Cell Protein?

The following basic steps are involved In SCP production:

1. Preparation of suitable medium with suitable carbon source
2. Cultivation of suitable strains of microorganism and fermentation
3. Separation of microbial biomass
4. Processing for consumption

Fig: Flow diagram of SCP Production

1. Selection of Suitable Microbial strain and medium:

a) This is the first and crucial step in SCP production.

b) The microbial strain should be selected carefully.

c) The microbes can cause toxicity, and hence its selection is based on the target consumer.

3. Separation of Microbial Biomass:

a) Many microbial colonies are developed from a single cell during fermentation.

b) By decantation method, the microbial colonies are isolated.

c) Isolated microbial cells are subjected to a variety of mechanical as well as chemical processes for the extraction of proteins and for further marketing purposes.

4. SCP Processing for development of Final Product:

a) This step includes treatment like centrifugation, washing, drying, etc.

b) The produced protein contains many impurities like carbohydrates, nucleic acids, salts, lipid contents, etc.

c) Pure protein isolation can be made by the disruption of the indigestible cell wall.

d) This can be done by different methods:

i) Mechanically by crushing, crumbling, grinding, pressure homogenization, etc.

ii) Chemically by enzyme treatments, NaCl, sodium dodecyl sulfate, etc.

iii) Physically by freezing, thawing, thermal shocks, heating, and drying.

d) Nucleic acids are removed by chemicals and mainly by enzymatic treatments using nuclease enzymes.

e) The final product is filtered, dried and packed for further consumption.

Advantages of Single Cell Protein

These are the following advantages of Single Cell Protein:

1. Microbes have a short cell cycle and thus have the ability to double up in a short duration. Thus, microbial biomass gets doubled within a short time.
2. Microbes can be easily genetically modified, and such GMOs can be used to produce high quality and quantity of proteins, along with various nutrients.
3. They contain high protein content.
4. They are not dependent on any climatic conditions, so they can be produced throughout the year.
5. They can be grown in a cheap and waste raw material in a simple setup like creating an artificial pond or large tanks. However, maintenance of sterile conditions and final processing is costly.
6. Production and utilization of SCP reduces environmental pollution.
7. SCP has a high content of vitamin B – Complex like Thiamine, Riboflavin and Folic acid, and also vitamin E.

Disadvantages of Single Cell Protein

The following disadvantages of Single Cell Protein are mentioned below:

1. The high content of amino acids leads to allergic reactions.
2. Excess consumption increases the obesity of a person.
3. It consists of a high concentration of nucleic acids, which leads to indigestion of purine bases.
4. It increases the levels of uric acid due to high nucleic acid content, causing Gout and kidney stone formation.
5. The SCPs production method is costly and requires highly sterilised conditions.
6. Majority of the microbes producing SCPs are generally fit for the consumption of animals only.

Uses of Single Cell Protein

1. Used as protein supplemented food – It provides supplements for malnourished children, and helps in reducing the problem of hidden hunger.

Fig: Supplemented food

2. Used as healthy food – It helps in reducing and controlling blood sugar levels in a person suffering from diabetes mellitus, provides healthy skin and eyes, and decreases bad cholesterol deposition and thus obesity.

Fig: Whey Protein

3. Used in cosmetics – It maintains healthy hair, used in many herbal beauty products like bio lipsticks, herbal face cream, etc.

Fig: Bio Lipstick

4. Used in poultry and cattle feed – The yeast protein is the only SCP product approved for human consumption, and the rest of the SCP can be used as animal feed.  It is mainly used to feed cattle, birds, fishes, etc., and is an excellent source of proteins and other nutrients.
5.SCP has a high protein content of about \(60\, – 80\% \) carbohydrates, low fats, vitamins \(({{\rm{B}}_1},{{\rm{B}}_2}\,{\rm{and}}\,{\rm{E)}}\) and minerals like calcium, potassium and phosphorus.

Summary

Single-cell protein (SCP) referred to the protein obtained from cells of microorganisms such as yeast, fungi, algae, and bacteria. SCP production may resolve the issue of deficiency of protein in an ever-increasing world population. The microbial SCP is produced from agricultural wastes. The whole organism or the dried cells of microorganisms are harvested and consumed. The SCP is used as a protein source for human food supplements and animal feeds. SCP can satisfy the world’s shortage of food while the population increases.

The yeast protein is the only SCP product approved for human consumption, and the rest of the SCP can be used as animal feed. The majority of SCPs can be grown on waste products and thus can help in reducing the problem of organic pollutants.

FAQs on Single Cell Protein

Q.1. What is Single Cell Protein?
Ans: New alternate and unconventional proteins are obtained from microbial sources like yeast, fungi, bacteria, and algae are named Single Cell Protein. SCP can be used as a food source or supplement.

Q.2. Write two examples of Single Cell Protein.
Ans: The two examples of Single Cell Proteins are Spirulina and Fusarium sp.

Q.3. What is the production of a Single Cell Protein?
Ans: The production of a Single Cell Protein includes several steps:
1. Preparation of suitable medium with suitable carbon source.
2. Cultivation of suitable strains of microorganism and fermentation.
3. Separation of microbial biomass.
4. Processing for consumption.

Q.4. Write two advantages of Single Cell Protein.
Ans: 1. Microbes have a short cell cycle and thus have the ability to double up in a short duration. Thus, microbial biomass gets doubled within a short time.
2. Microbes can be easily genetically modified, and such GMOs can be used to produce high quality and quantity of proteins, along with various nutrients.

Q.5. Write disadvantages of single-cell protein.
Ans: 1. The high content of amino acids leads to allergic reactions.
2. Excess consumption increases the obesity of a person.
3. It consists of a high concentration of nucleic acids, which leads to indigestion of purine bases.
4. It increases the levels of uric acid due to high nucleic acid content, causing Gout and kidney stone formation.

Q.6. Does single-cell protein have high protein content?
Ans: Yes, SCP has high protein content.

Q.7. Who coined the term Single Cell Protein?
Ans: The term SCP was coined by Carol L Wilson in \(1966\) at the Massachusetts Institute of Technology – USA.

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