Single cell protein

SCP – PRODUCTION
& ADVANTAGES
Dr. Anu P. Abhimannue
Department of Biotechnology,
St. Mary's College,
Thrissur

Introduction
■ Crude or refined 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.
■ The microorganisms utilize the carbon and nitrogen present in the biomass and
convert them into high-quality proteins.
Dr.Anu P.Abhimannue, St. Mary'sCollege,Thrissur. 2

Dr.Anu P.Abhimannue, St. Mary'sCollege,Thrissur.
3

Microorganisms for SCP production
■ Algae: Members of the genera Chlorella, Scenedesmus and Spirulina are generally grown
in ponds/tanks.They use CO2 and sunlight as substrate which are without any cost.

Disadvantages
■ Rich chlorophyll content which is not suitable for human use,
■ Serious problems when Chlorella and Scenedesmus are used in human diet (Spirulina is
more suited tor human use),
■ Low cell density, e.g., 1-2 g dry weight/l,
■ Serious risk of contamination
■ Costly recovery methods for unicellular algae

Filamentous Fungi
■ Fusarium - utilize simple carbohydrates and can produce an important SCP- mycoprotein
which is used for human consumption.
■ Phanerochaete chrysosporium - one of the most studied lignin degraders
■ Mushrooms - The basidiomycetes or mushroom-type fungi have long been grown on
lignocellulosic materials such as wood and straws and to produce edible mushrooms. The
cultivation of edible mushrooms plays a prime role in the production of SCP; it is used
directly as a human food.

Diasdavantages
■ Slower growth rates than bacteria and yeast, but some micro-fungi may be comparable
to yeast,
■ Contamination by yeast may be frequent if sterility is not maintained, while that by
bacteria can be minimised by keeping the pH of broth below 5,
■ They have high nucleic acid content (upto 15% RNA) which must be reduced, and
■ The strains have to be thoroughly evaluated for mycotoxin production. However, a
substantial part of the N may be present in chitin, a component of the cell wall.

Yeasts
■ Members of Saccharomyces, Candida andTorulopsis
■ Disdavantages:
– Slower growth rates than fastest growing bacteria,
– High nucleic acid content (upto 15%) which needs to be reduced, and
– Methionine supplementation may be done to overcome S-containing amino acid
deficiency of its proteins.

Bacteria
■ Methylophilus Methylotrophus, Pseudomonas,Cellulomonas and Alcaligenes
■ Disadvantages:
– High nucleic acid, especially, RNA content (ca. 20%) which must be reduced,
– Sterility must be maintained during the production process since pH of cultures is kept
between 5 and 7,
– Risk of contamination by pathogenic bacteria is considerable,
– Recovery of cells is problematic, and
– Careful evaluation for endotoxin production is essential particularly when gram-
negative bacteria are used.

Production
■ The production is carried out in the following steps:
– Selection of suitable strain.
– Media preparation
– Fermentation.
– Separation & downstream processing

Selection of suitable strain
■ A suitable microbial strain must have several characteristics:
1. Growth rate, productivity and yields on the specific, low-cost, substrates to be used;
2. Temperature and pH tolerance;
3. Oxygen requirements, heat generation during fermentation and foaming
characteristics;
4. Growth morphology and genetic stability in the fermentation;
5. Ease of recovery of SCP and requirements for further downstream processing;
6. Structure and composition of the final product, in terms of protein content, amino acid
profile, RNA level, flavor, aroma, color and texture.
7. Safety and acceptability
11

Media preparation
■ Must have 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.

Fermentation
■ Continuous fermentations are generally used, which are operated at close to the
organism’s maximum growth, to fully exploit the superior productivity of continuous
culture.
■ SCP processes are highly aerobic (except those using algae). Therefore, adequate
aeration must be provided.
■ cooling is also necessary as considerable heat is generated

Separation & downstream processing
■ The cells are separated from the spent medium by filtration or centrifugation and may
be processed in order to reduce the level of nucleic acids.
■ RNase activity is retained and degrades RNA to nucleotides that diffuse out of the
cells.
■ Depending upon the growth medium used, further purification may be required, such
as a solvent wash
■ Further proceeded to pasteurization, dehydration and packaging.

Substrates
■ The most commonly used raw materials may be grouped in the following categories.
1. High-energy sources e.g. alkanes, methane, methanol, ethanol, gas oil.
2. Waste products e.g. molasses, whey, sewage, animal manures, straw, bagasse.
3. Agricultural and forestry sources e.g. cellulose, lignin.
4. Carbon dioxide, the simplest carbon source.

From alkanes
■ Two types of petroleum products are mainly used for this purpose.
– Gas oil or diesel oil containing 10-25% of alkanes with carbon length C15-C30 (i.e.
long chain alkanes).
– Short chain alkanes with carbon length in the range of C10-C17, isolated from gas oil
by use of molecular sieves.
■ Alkanes can be degraded by many yeasts, certain bacteria and fungi.

■ The most important step in scp production through alkanes is the introduction of
oxygen which can be brought out by two pathways-terminal oxidation and sub-
terminal oxidation.

From methane
■ Certain bacteria that can utilize methane for SCP production have been identified e.g.
Methylococcus capsulatus, Methylomonas methanica, Methylovibrio soehngenii. So far,
yeasts that can utilize methane have not been identified.
■ The bacterial enzyme methane oxygenase oxidizes methane to methanol, which can
be converted to formaldehyde and then to formic acid

From methanol
■ Methanol as a carbon source for SCP has several advantages over alkanes and methane.
– Easily soluble in aqueous phase at all concentrations
– No residue of it remains in the harvested biomass.
– Technically, methanol can be easily handled.
– The sources for methanol are natural gas, coal, oil and methane.
■ Bacteria producing SCP from methanol - Methylobacter, Arthrobacter, Bacillus,
Pseudomonas, Vibrio
■ Yeasts - Candida biodinii, Hansenula sp,Torulopsis sp
■ Fungi - Trichoderma lignorum, Gliocladium delinquescens

From methanol

From waste
■ These include the conversion of low-cost organic wastes to useful products, and
reduction in environmental pollution.
■ However, there has been very limited success for the large scale production of SCP
from wastes.
■ This is mainly because of transportation cost and technical difficulties.
■ The technology adopted and the organism employed for SCP production depends on
the waste being used as the substrate.
■ Thus, Saccharomyces cerevisiae is used for molasses, Kluyveromyces fragile for cheese
whey.

Symba process
Symba process is a novel technology developed in Sweden to produce SCP by utilizing
starchy wastes by employing two yeasts, Endomycopsis fibuligira and Candida utilis. The
Symba process is carried out in three phases.
■ Phase I: The waste material containing starch is sterilized by passing through a heat
exchanger.
■ Phase II: The sterilized material is passed through two bioreactors. The first reactor
contains E. fibuligira which hydrolyses starch. When this hydrolysate is passed to the
second bioreactor, the organism,C. utilis grows to form biomass.
■ Phase III: The microbial biomass can be separated by centrifugation. The samples of SCP
can be dried, packaged and stored.

Commercial SCP
■ Pekilo — a fungal protein rich product from filamentous fungus, Paecilomyces variotii,
■ Quorn - the mycoprotein for humans produced by the fungus Fusarium graminearum
■ ICI pruteen - The single-cell protein produced by ICI from methanol and ammonia using
M. methylotrophus was referred to as ICI pruteen

Mushrooms
Mushrooms are fungi belonging to the classes
basidiomycetes (Agaricus sp, Auricularia sp,
Tremella sp) and ascomycetes (Morchella sp,
Tuber sp). Majority of edible mushrooms are the
species of basidomyces.

Nutritive value of edible mushrooms
■ Some people regard edible mushrooms as vegetable meat. Mushrooms contain 80-90%
water, protein (35-45% of dry weight), fats and free fatty acids (7-10%), carbohydrates (5-
15%) and minerals in good concentration.
■ Certain undesirable substances may also be present in edible mushrooms e.g. cadmium,
chromium.

Mushroom production
26

Advantages of edible mushroom
1. Mushrooms can be produced by utilizing cheap and often waste substrates (industrial and
wood wastes).
2.They are of high nutritive value being rich in proteins, vitamins and minerals.
3. Many delicious recipes can be prepared from mushrooms.
4. Due to low carbohydrate content, consumption of mushrooms is advocated to diabetic
patients.

Applications
■ Provides instant energy.
– It is extremely good for healthy eyes and skin.
– Provides the best protein supplemented food for undernourished children.
– Serves as a good source of vitamins, amino acids, minerals, crude fibres, etc.
■ Used in therapeutic and natural medicines for:
– Controlling obesity.
– Lowers blood sugar level in diabetic patients.
– Reducing body weight, cholesterol and stress.
– Prevents accumulation of cholesterol in the body.

Applications
■ Used in Cosmetics products for:
– Maintaining healthy hair.
– Production of different herbal beauty products, like- Biolipstics, herbal face cream, etc.
■ Used in Poultry:
– As it serves as an excellent and convenient source of proteins and other nutrients, it is
widely used for feeding cattle, birds, fishes etc.

References
■ https://uomustansiriyah.edu.iq/media/lectures/6/6_2017_02_21!09_55_06_PM.pdf
■ http://www.biologydiscussion.com/single-cell-protein/production-of-single-cell-
protein-and-mushrooms/10392
■ http://www.biotechnologynotes.com/industrial-biotechnology/single-cell-
protein/single-cell-protein-scp-production-substrates-microorganisms-advantages-
challenges-biotechnology/14143
■ http://www.biologydiscussion.com/food-microbiology/single-cell-protein-scp-
production-and-advantages/55699
■ https://byjus.com/biology/single-cell-protein/

Single cell protein

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