What is Single Cell Protein

Single Cell Protein

(Sources, Micro-Organism, Process, Nutritive Value, Advantages and Limitations)

HISTORY- Single-cell proteins (SCP) or microbial proteins refer to edible unicellular microorganisms. In 1781, processes for preparing highly concentrated forms of yeast were established. Research on Single Cell Protein Technology started a century ago when Max Delbruck and his colleagues found out the high value of surplus brewer’s yeast as a feeding supplement for animals.

1.      The name "single cell protein" was used for the first time, in 1967 by the M.I.T. (Massachusetts Institute of Technology) professor Carol Wilson to give a better image than "microbial protein". During the sixties the idea that the single cell protein could help the less developed countries in future food shortages was gaining research interest among scientists in universities and industry, particularly in oil. The result was the development of SCP technology either for livestock or for human consumption.

2.      In 1950’s British Petroleum initiated production of SCP on commercial basis.

3.      Pruteen was the 1st commercial SCP used as animal feed additive

4.      Pruteen was produced from bacteria Methylophilus methylotrophus cultured on methanol & had 72 % protein content.

SCP PRODUCTION IN INDIA- National Botanical Research Institute (NBRI), Central Food Technological Research Institute (CFTRI)., In CFTRI, SCP is produced from algae cultured on sewage

What is Single Cell Protein -SCP?

Single-cell protein refers to the crude, a refined or edible protein extracted from pure microbial cultures, dead, or dried cell biomass. They can be used as a protein supplement for both humans or animals.

Microorganisms like algae, fungi, yeast, and bacteria have very high protein content in their biomass. These microbes can be grown using inexpensive substrates like agricultural waste viz. wood shavings, sawdust, corn cobs etc. and even human and animal waste.

The microorganisms utilize the carbon and nitrogen present in these materials and convert them into high-quality proteins which can be used as a supplement in both human and animal feed. The single-cell proteins can be readily used as fodder for achieving fattening of calves, pigs, in breeding fish and even in  Animal Husbandry – Poultry and Cattle Farming.

Single Cell Protein (SCP) offers an unconventional but plausible solution to this problem of protein deficiency being faced by the entire humanity.

Source

Single cell protein can be produced on a number of different substrates, often this is done to reduce the Biological Oxidation Demand of the effluent streams leaving various type of agricultural processing plants. The term single cell protein (SCP) refers to dead, dry cells of micro-organisms such as yeast, bacteria, fungi and algae which grow on different carbon sources.

Micro-Organism

A list of the microorganisms used for the production of Single Cell Protein is as follows:

Fungi

• Aspergillus fumigatus
• Aspergillus niger
• Rhizopus cyclopean

Yeast

• Saccharomyces cerevisiae
• Candida tropicalis
• Candida utilis

Algae

• Spirulina sps
• Chlorella pyrenoidosa
• Chondrus crispus

Bacteria

• Pseudomonas fluorescens
• Lactobacillus
• Bacillus megaterium

Here are the average compositions of the different microorganisms present in the % dry weight of Single-cell protein.

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

 

Production of Single-Cell Protein

The production is carried out in the following steps:

1. Selection of suitable strain.
2. Fermentation.
3. Harvesting.
4. Post-harvest treatment.
5. SCP processing for food.

Like any other microbial culture, production of pure microbial cultures for desired protein products requires a  nitrogen source, sources of carbohydrates and other nutrients like phosphorus to support optimal growth of the culture. Contamination is prevented by maintaining strict sterile conditions throughout the process. The components of the culture media are either heat sterilized or filtered through microporous membranes. The selected microorganism is then inoculated in pure conditions. Most of the processes are highly aerobic, except algal fermentation; hence a good supply of oxygen is an indispensable requirement. After the multiplication of the biomass, it is recovered from the medium and purified further for enhanced usefulness and or storability.

1)      Selection of strain-

i)       It a very critical step as the quality of protein depends totally on the microbe that is used for the production.

ii)     Thus careful selection of the strain should be done.

iii)  Care should be taken that the selected strain should not produce any toxic or undesirable effects in the consumer.

2)      Fermentation

i)       It can be carried out in the fermentor which is equipped with aerator, thermostat, pH, etc. or in the trenches or ponds.

ii)     Microbes are cultured in fed- batch culture.

iii)  Engineers have developed deep lift fermentor & air lift fermentor.

3)      Harvesting

i)       When the colonies of microbes are fully developed, they are then harvested.

ii)     The bulk of cells are removed from the fermentor by decantation.

4)      Post harvest treatment

a)      After harvesting, the cells are subjected to a variety of processes.

b)      Post harvesting treatments includes steps like separation by centrifugation, washing, drying, etc.

PROCESSING FOR FOOD

It includes

1.      Liberation of cell proteins by destruction of indigestible cell wall.

A. MECHANICAL METHODS- Crushing, crumbling, grinding, pressure homogenization, etc.

B. CHEMICAL METHODS

i)       Enzymes & salts are used to digest or disrupt the cell wall.

ii)     Salts like NaCl, sodium dodecyl sulfate, etc. whereas nuclease enzymes are used

C. PHYSICAL METHODS-Freeze- thaw, osmotic shock, heating & drying.

2. Reduction of nucleic acid content

·  Chemical & enzymatic treatments are preferred.

·  Chemicals which are used includes acidified alcohol, salts, acids & alkalies.

·  Use of such chemicals leads to formation of lygino-alanine which causes hypersensitivity skin reactions.

·  Enzymes which are used include ribonuclease & nuclease enzymes.

·  These enzymes can be used exogenously or can be induced endogenously.

Advantages of Single-Cell Protein

Large-scale Single-Cell Protein production has multiple advantages over conventional food production practices such as:

• Microorganisms have a high rate of multiplication which means a large quantity of biomass can be produced in a comparatively shorter duration.
• The microbes can be easily genetically modified to vary the amino acid composition.
• A broad variety of raw materials, including waste materials, can be used as a substrate. This also helps in decreasing the number of pollutants.
• Production is independent of climatic conditions.

Disadvantages of Single-Cell Protein

In spite of many advantages, there are few drawbacks. Single-Cell Protein has not been widely accepted for human consumption owing to certain problems as follows:

• High level of nucleic acid in biomass makes it difficult for consumption as it may lead to gastrointestinal problems.
• The biomass may trigger an allergic reaction if the digestive system recognizes it as a foreign product.
• The presence of nucleic acids in high content leads to elevated levels of uric acid.
• In certain cases, the development of kidney stone and gout if consumed in high quality.
• Possibility for the presence of secondary toxic metabolites which results in Hypersensitivity and other skin reactions.
• The capital cost of production is high as sophisticated machinery is required.

Applications of Single-Cell Protein

1. Provides instant energy.
2. It is extremely good for healthy eyes and skin.
3. Provides the best protein supplemented food for undernourished children.
4. Serves as a good source of vitamins, amino acids, minerals, crude fibres, etc.

• Used in therapeutic and natural medicines for:

1. Controlling obesity.
2. Lowers blood sugar level in diabetic patients.
3. Reducing body weight, cholesterol and stress.
4. Prevents accumulation of cholesterol in the body.

• Used in Cosmetics products for:

1. Maintaining healthy hair.
2. Production of different herbal beauty products, like- Biolipstics, herbal face cream, etc.

• Used in Poultry:

1. As it serves as an excellent and convenient source of proteins and other nutrients, it is widely used for feeding cattle, birds, fishes etc.

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