SINGLE-CELL PROTEIN (SCP)
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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”
Single-cell proteins develop when microbes ferment waste materials (including
wood, straw, cannery, and food-processing wastes, residues from alcohol
production, hydrocarbons, or human and animal excreta).
60-80% dry cell weight; contains nucleic acids, fats, CHO, vitamins and
minerals Rich in essential amino acids (Lys-Met)
The problem with extracting single-cell proteins from the wastes is the dilution
and cost.
Found in very low concentrations, usually less than 5% .
Engineers have developed ways to increase the concentrations including
centrifugation, flotation, precipitation, coagulation, and filtration, or the use of
semi-permeable membranes.
ADVANTAGES OF USING MICROORGANISMS
1. MO grow at very fast rate under optimal conditions
2. Quality and quantity is better than higher plants and animals
3. Wide range of raw materials can be used
4. Culture and fermentation conditions are simple
5. MO can be genetically manipulated
Advantages of SCP over conventional protein sources are:
It has high protein and low fat content.
It is good source of vitamins particularly B-complex. e.g. Yeasts
It can be produced through-out the year.
Waste materials are used as substrate for the production of these
proteins.
It reduces the environmental pollution and helps in recycling
of materials.
SCP organisms grow faster and produce large quantities of SCP from
relatively small area of land and time.
These have proteins with required amino acids that can be easily
selected by genetic engineering.
During the production of SCP biomass, some organisms produce useful
by products such as organic acids and fats.
It can be genetically controlled.
It causes less pollution.
Algal culture can be done in space which is normally unused.
Factors that impairs the usefulness of Unicellular biomass
- All single-celled microorganisms of interest from the industrial point of view
have a nondigestible envelope, which makes protein assimilation difficult.
- The content of nucleic acids in the unicellular biomass is higher than the
permissible level and may cause disorders of purine metabolism in the human
body.
- The biomasses of some unicellular microorganisms have an unpleasant color
(algae), taste, and smell, which make them unsuitable even for animal
consumption.
- Food grade production of SCP is more expensive than other
sources of proteins, as it depends on the raw materials.SCP
for human consumption is 10-12 times more expensive than
SCP for animal feed.
- Digestion of microbial cells is rather slow, and is frequently
associated with indigestion and allergy reactions.
“Possible Substrates for SCP”
They can be subdivided into three categories:
 High energy sources (natural gas, n-alkanes, gas-oil, methanol, ethanol, acetic
acid);
 Different wastes (molasses, sulfite waste liquor, milk, whey, fruit wastes); and
 Renewable plant resources (sugar, starch, cellulose).
A wide range of substrates can be used to grow microbial proteins
• whey, orange peel residue, sweet orange residue, sugarcane bagasse, paper mill
waste, rice husks, wheat straw residue, cassava waste, sugar beet pulp, coconut
waste, yam waste, banana pulp, mango waste, grape waste, sweet potato
Other nutritional parameters which evaluate the quality of a given SCP are:
- the digestibility (D)
- the biological value (BV)
- the protein efficiency ratio (PER)
- the net protein utilisation (NPU)
The quality of SCP is an important factor for commercial production.
1. First parameter which reflects the quality of a protein, is the is the percentage of
the total nitrogen Digestibility Coefficient (DC) consumed which is absorbed from
the digestive tract.
2. Estimation of the Biological Value (BV) is a measure of nitrogen retained for
growth or maintenance.
3. An accurate method to evaluate the quality of proteins is the determination of the
Protein Efficiency Ratio (PER), expressed in terms of weight gain per unit of
protein consumed by the test animal in short-term feeding trials.
4. Finally, the Net Protein Utilization (NPU) -equivalent to the calculation BVxDCis a measure of the digestibility of the protein and the biological value of the
amino acids absorbed from the food.
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Production of SCP involves following steps:
Selection of Strain of microbe and Substrate
Fermentation
Harvesting
Post harvest treatment
Processing of SCP
Selection of Strain of Microbe & Substrate:
• 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.
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.
Harvesting
• For the producing and harvesting of microbial proteins cost is a major problem.
• There are many methods available for concentrating the solutions like filtration,
precipitation, centrifugation and the use of semi-permeable membranes.
• The equipment used for these methods of de-watering is expensive and so would
not be suitable for small scale productions and operations.
• Single cell proteins need to be dried to 10% moisture or they can be condensed
and denatured to prevent spoilage.
Post-harvesting Fermentation:
• Isolated microbial colonies are subjected to various differential techniques.
• E.g. Centrifugation, Washing, Drying etc.
• 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
APPLICATIONS
1. As protein supplemented foodAlso source of vitamins, amino acids, minerals, crude fibers, etc.
• Supplemented food for undernourished children.
2. As health food• Controls obesity
• Provides instant energy .
• Example- Spirulina- part of diet of US Olympic team.
3. In therapeutic and natural medicines• Reduce body weight, cholesterol, stress.
• Lowers blood sugar level in diabetic(due to presence of B - linolenic acid)
• Prevents accumulation of cholesterol in body.
• Healthy eyes and skin (beta carotene)
• Beta carotene ( anti cancer substance-UN National Cancer Research Institute)
• Increase lactation.
4. In cosmetics• Important role in maintaining healthy hair (vitamin A and B).
• Many herbal beauty products.
• Biolipstics and herbal face cream(Phycocyanin).
• Capable of replacing coal tar dye based cosmetics.
5. Poultry and cattle feed• Excellent, convenient source of protein and other nutrients.
• Used to feed cattle, fishes etc.
5. In the technical field as: Paper processing, leather processing and as foam
stabilizers.
THANK YOU
-PHARMA STREET