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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