Single Cell Protein (SCP): Microbes, Production, Uses

Single Cell Protein is the dried cells of microorganisms consumed as a protein supplement by humans or animals.

The protein is derived from cells of micro-organisms such as yeast, fungi, algae, and bacteria which are grown on various carbon sources for synthesis.

Single Cell Protein (SCP)
Single Cell Protein (SCP)

With the increase in population and worldwide nutrient deficiency, the use of microbial biomass as food and feed is highlighted.

SCPs contain vitamins, e.g., thiamine, riboflavin, pyridoxine, nicotinic acid, pantothenic acid, folic acid, biotin, cyanocobalamin, ascorbic acid, β-carotene and α- tocopherol; essential amino acids, represented by lysine and methionine; minerals; nucleic acids and lipids.

The microorganisms used in single-cell protein production should have the following properties.

  1. Absence of pathogenicity and toxicity
  2. Protein content and quality
  3. Digestibility and organoleptic qualities
  4. Growth rate
  5. Adaptability to unusual environmental conditions such as pH, temperature, and mineral concentrations.
  6. Ability to utilize carbon and nitrogen sources.

Interesting Science Videos

History of Single Cell Protein (SCP)

  • The SCP was first developed during World War I.
  • In 1919, Sak in Denmark and Hay duck in Germany invented a method named Zulaufverfahren in which sugar solution was fed to an aerated suspension of yeast instead of adding yeast to the diluted sugar solution.
  • Saccharomyces cerevisiae was produced in Germany from molasses to replace protein.
  • Candilaarborea and C. utilis were used during the Second World War.
  • Similarly, during World War II Candida utilis was used in soup and sausage.
  • Many industries were established in the USA and Europe, especially for C. utilis production after the war.
  • During the 1960s and 1970s, production industries were established in the UK, France, Italy, Russia, Japan, and Taiwan.
  • The term single-cell protein was coined by Carol L. Wilson in 1966.
  • In the 1960s, researchers at British Petroleum developed a technology called the proteins-from-oil process for producing
  • Initial research work was done by Alfred Champagnatar and BP s Lavera, Oil Refinery in France; a small pilot plant there started operations in March 1963.
  • Champagnat was awarded with the UNESCO Science Prize in 1976.
  • The Soviets were opening large “BVK” (belkovo-vitaminny kontsentrat, i.e., “protein-vitamin concentrate” plants next to their oil refineries in Kstovo (1973) and Kirishi (1974). 
  • The Soviet Ministry of Microbiological Industry had eight plants by 1989 but when the environmentalist movements began to give pressure on the government, they decided to close them down or convert to some other microbiological processes.
  • In 1973, a few species of actinomycetes and filamentous fungi were reported for protein production by using various substrates, at Second International Conference which was held at MIT.
  • In recent times, among the European Communist countries, Russia has had the greatest capacity for SCP production, with at least 86 plants in operation, using different substrates.

Organisms used as Single Cell Protein (SCP) and the substrate used for their production

1They are phototrophic organisms.They can be divided into unicellular yeast and mold.
2They are potential SCP due to their chemical composition which contains proteins, essential fatty acids mainly omega-3 fatty acids, and several bioactive compounds. They have relatively low nucleic acid content (3–8%).Bacteria are potential SCP as they possess high protein content (50-80%) along with vitamins, phospholipids, and other functional molecules. They are capable of growing on a wide range of substrates from carbohydrates to gaseous and liquid hydrocarbons Yeasts are mainly used in aquaculture as it is the protein-rich ingredient in aquafeeds, with crude protein contents of 38–52%.Mold is found to be highly digestible by fish.
3The advantages of using algae include simple cultivation, effective utilization of solar energy, faster growth, and high protein andThe advantages of using bacteria are its use of a wide range of substrates, their short time for generation, production of vitamins and micronutrients.The advantages of using yeasts include a high level of malic acid content, can grow in acidic pH and is easy to harvest.The advantages of using mold include high nucleic content of up to 10%.
4The potential disadvantage is the economical limitations of scale-up, digestibility (need for cell wall disruption to release nutrients), the large surface area needed for cultivation, and contamination risk in an open pond.The potential disadvantages are palatability issues, high content of nucleic acid, and production of toxins.The potential disadvantages include the possible presence of the toxin, slower growth rate, and lesser content of protein (45- 65%).
5Examples: Tetraselmis suecica, Isochrysis galbana, Dunaliella tertiolecta, Chlorella stigmatophora, Spirulina spp.Examples: Mthylobacterium extorquens, Mrthylococcus capsulatus, Rhodobacter sphaeroides, and Afifella marina.Examples: Yeast: Saccharomyces cerevisiae, kluyveromyces marxianus.Fungi: Aspergillus oryzae, Yarrowia lipolytica.
Microorganisms used in SCP production and their main characteristics
Figure: Microorganisms used in SCP production and their main characteristics. Image Source: Antia G. Pereira et al. 2022.

Fungi and substrates utilized by them and the protein content produced

S.N.SubstrateFungiProtein content
1Maltose, GlucoseAspergillus fumigatus,
Rhizopus chinensis
2Cellulose, HemicelluloseAspergillus niger,
A. oryzae,
Cephalosporium eichhorniae, Chaetomium cellulolyticum
3Glucose, Lactose, GalactosePenicillium cyclopium
5HydrocarbonsYarrowia lipolytica
Candida tropicalis
6EthanolCandida utilis
7MethanolPichia spp.Pichia pastoris
8Cellulose, PentoseScytalidium aciduphilium, Thricoderma viridae,
Thricoderma alba
9GlucoseFusarium venenatum44
10Sulphite waste liquorPaecilomyces varioti
Candida utilis
11Starch, GlucoseFusarium graminearum
12StarchSaacharomycopsis fibuligera
Candida utilis
Saccharomyces cerevisiae
14Banana waste

Apple pomace

Citrus pulp

Potato starch processing waste

Waste liquor
Aspergillus niger18




15Orange peelAspergillus niger
Rhizopus oryzae
Aspergillus niger
Saccharomyces cerevisiae
16Banana peelAspergillus terreus
17Bergamot fruit (citrus fruit) peelPenicillium roqueforti,
Penicillium camemberti
18Banana peel, pineapple peel, papaya peelPhanerochaete chrysosporium,
Panus tigrinus
Phanerochaete chrysosporium
19Papaya waste, cucumber peelings, pomegranate fruit rind, pineapple fruit skin, and watermelon skinRhizopus oligosporus
20Orange peelTrichoderma viride,
Trichoderma reesei
21Orange pulp and brewer’s spent grain

Dried potato and carrot skins

Cucumber peels and orange peels

Discarded foods (mix of fruits and vegetables)
S. cerevisiae



22Cheese wheyCandida krusei48
23Whey and potato pulpK. marxianus33.7
24Juice, pulp, and peel from oranges and lemons

Corn stover effluent
R. opacus


Candida tropicalis56

26Rice branCladosporium cladosporioides
Penicillium citrinum
Aspergillus flavus
Aspergillus niger
Aspergillus ochraceus
Fusarium semitectum and sp1 and sp2
Monascus ruber

27Wheat strawPleurotus florida63
28LigninChrysonilia sitophi39
29Rice bran (deoiled)Aspergillus oryzae24
30Cheesy whey filterTrichoderma harzianum34
31Citrus pulpTrichoderma virideae32
32Waste capsicum powder
Poultry litter
Potato starch industry waste
Potato wastewater
Candida utilis29
33Spoiled date palm fruitHanseniaspora uvarum
Zygosaccharomyces rouxi
34Cheese whey

Orange pulp, molasses, brewer’s spent grain, whey, potato pulp, malt spent
Kefir spp.54

35Brewery’s spent grains (hemicellulosic hydrolysate)Debaryomyces hansenii32
36Liquid sucroseHansenula jadinii
37Cheese whey

Orange pulp, molasses, brewer’s spent grain, whey, potato pulp
Kluyveromyces marxianus43

38Inulin, crude oil, glycerol waste hydrocarbonsYarrowia lipolytica48-54

Algae and substrates utilized by them and the protein content produced

S.N.SubstrateAlgaeProtein content
1Anabaena cylindrica43-56
2Aphanizomenon flosaquae62
3Arthrospira maxima56-77
4Chlorella ellipsoidea42.2
5Chlorella ovalis10.97
6Chlorella pyrenoidosa57
7Chlorella spaerckii6.87
8Chlorella vulgaris51-58
9Dunaliella primolecta12.26
10Dunaliella salina57
11Dunaliella tertiolecta11.4
12Porphyridium aerugeneum31.6
13Porphyridium cruentum28-39
14Scenedesmus almeriensis41.8
15Scenedesmus obliquus50-55
16Spirulina platensis60-71
18Tetraselmis chuii31-46.5
19Soda ash effluentChaetomorpha antennina
Ulva fasciata Chlorella
20Tofu waste

Tempeh waste

Cheese waste
Chlorella spp.52.32


21Saline sewage effluentsChlorella salina51
22Natural habitatGracilaria domingensis
Gracilaria birdiae
Laurencia filiformis
Laurencia intricate
Chondrus crispus
Porphyra umbilicalis
Gracilaria verrucosa
23WastewaterChlorella sorokiniana
Scenedesmus obliquus
24Salinated water

Desalinated water

25CO2 and sunlightChlorella pyrenoidosa
Scenedesmus quadricauda
Spirulina maxima
26n-Alkanes, keroseneCandida intermedia,
C. lipolytica,
C. tropicalis,
Nocardia spp
27Nannochloropsis spp.39.3
28Nannochloropsis gaditana39.3
29Desmodesmus spp37.3
30Schizochytrium spp9.4-42.5
31Chlorella vulgaris17.9
32Scenedesmus spp48

Bacteria and substrates utilized by them and the protein content produced

S.N.SubstrateBacteriaProtein content
1Orange wastes, lemon wastesRhodococcus opacus
2Commercial shrimp feedAfifella marina STW181>46
3Ram hornBacillus cereus
Bacillus subtilis
Escherichia coli
4Potato starch processing wasteBacillus licheniformis
Bacillus pumilis
5Soybean hullBacillus subtilis spp26
6Collagen meat packing waste in a fermenterBacillus megaterium
7Glucose, fructoseCorynebacterium ammoniagenes61
8CelluloseCellulomonas spp
Alcaligenes spp
9WheyLactobacillus bulgaricus
Candida krusei
10Synthetic growth mediumCupriavidus necator
Rhodopseudomonas spp.
Rhodobacter capsulatus
Rhodopseudomonas acidophila
11Petrochemical wastewaterHaloarcula sp. IRU176
12Methane (natural gas)Methylococcus capsulatus,
Ralstonia sp.,
Brevibacillus agri
13Gas and liquid products of sewageMethylomonas and Methylophilus<41
14MethanolMethylophilus methylotrophus
Methylomonas clara
15MethaneMethylomonas spp. (Methanomonas)
Methylococcus capsuiatus
Trichoderma spp.
16EthanolAcinetobacter calcoaceticus
17Diesel oil in fermenterAchromobacter delvacvate
18Supernatant and biogasMethylophilus spp24
19Natural gasMethilomonas.spp69.3
20Brewery wastewaterRhizospheric diazotrophs>55
21Wastewater from a latex rubberRhodopseudomonas blastica66.7
22Sludge and sago starch processingRhodopseudomonas palustris72-74
23Poultry slaughterhouse wastewaterRhodocyclus gelatinosus67.6
24Pineapple wasteRhodobacter sphaeroides P4766.6
25Fermented pineapple extractRhodopseudomon as palustris P165
26Soyabean wastewaterRhodobacter sphaeroides Z0852
27Glutamate malate mediumRhodovulvum sulphidophilum15.6
28Pig farm wasteRhodocyclus gelatinosus50.6
29Sugar refinery wastewaterRhodopseudomonas and R. fulvum58
30Miso-like effluent mediumRhodocyclus gelatinosus63
31Dehydrated medium from pineapple peel wasteRhodobacter sphaeroides P4766.6
32Seafood processing wastewaterRhodocyclus gelatinosus50
33Wastewater from noodleRhodopseudomonas palustris50
34Municipal wastewaterRhodopseudomonas spp. CSK0160.1
35Tuna condensateRhodocyclusg elatinosus R756
36Cassava wasteRhodocyclus gelatinosus45
37Simulated wastewaterRhodopseudomonas palustris45
Photosythetic sludgeRhodopseudomonas palustris74

Single Cell Protein production method

  1. Selection of substrate and strain
  • The fast-growing microorganisms are selected that are rich in protein content and possess suitable growth characteristics.
  • Then suitable substrates are chosen that are essential for the growth of selected microorganisms.
  1. Fermentation
  • A fermenter is an instrument, which is set up to carry out the process of fermentation mainly the mass culture of plant or animal cells.
  • The inoculated medium is then placed in a fermenter where the microorganisms grow and multiply. The conditions inside the fermenter, such as temperature, pH, and oxygen levels, are carefully controlled to optimize the growth of the microorganisms.
  1. Harvesting
  • After fermentation, the microbial cells are harvested and separated from the growth medium.
  • However, the harvesting and purification after production of SCP production remain a problem.
  1. Post-harvest treatment
  • The harvested microbial cells are then dried to preserve them and reduce their volume, making them easier to store and transport.
  1. SCP processing for food
  • The dried cells are then processed to remove impurities, improve their nutritional content, and enhance their flavor and texture.
Optimal single-cell protein (SCP) production processes, integrating circular economy approaches.
Figure: Optimal single-cell protein (SCP) production processes, integrating circular economy approaches. Image Source: Antia G. Pereira et al. 2022.

Advantages of Single Cell Protein

Microorganisms are usually used for the production of SCP because of the following advantages.

  1. Microorganisms grow at a faster rate compared to the growth of protein-rich grain which takes a year for production.
  2. The quality and quantity of protein are better (60-80%).
  3. A wide range of inexpensive raw materials can be used easily.
  4. The production process is easy and simple.
  5. The microorganisms can be easily subjected to genetic manipulation.
  6. The microorganism can be produced all-around a year.
  7. They can utilize a wide range of substrates.
  8. The production of SCP is eco-friendly, cost-effective, and energy efficient.

Disadvantages of Single Cell Protein

  1. The production of SCP is a complex process that requires strict control over various environmental factors.
  2. Maintaining the quality of SCP is a hard job as the harvesting and purification after production of SCP production remains a problem.
  3. SCP is not a suitable source of all the essential amino acids, so it is typically used as a supplement to other protein sources
  4. Despite the many potential benefits of SCP, consumer perception remains a significant challenge, as many people may be skeptical of consuming a product derived from microorganisms.

Applications of Single Cell Protein

  • In animal feed and nutrition, for the stuffing and fattening of poultry, laying hens, calves, and pigs.
  • As food additives (vitamin and aroma carriers and emulsifying agents), to enhance nutritional value (of baked food items, ready-made meals, soups, etc.), and as starter cultures (baker’s, brewer’s, and wine yeast).
  •  In industrial processes, as a foam-stabilizing agent, and in paper and leather processing.
  • SCP provides the best protein-supplemented food for undernourished children as it serves as a good source of vitamins, amino acids, minerals, etc. 
  • They are used in therapeutic and natural medicines for controlling obesity, lowers the blood sugar level in diabetic patients, reduces body weight, cholesterol, and stress, and prevents the accumulation of cholesterol in the body. 
  • SCP is used in Cosmetics products for maintaining healthy hair, production of different herbal beauty products, like- Biolipstics, herbal face cream, etc.


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About Author

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Sanjogta Thapa Magar

Sanjogta Thapa Magar has done Master’s degree (M.Sc.) in food microbiology from St. Xavier’s college. Currently, she is working as a Quality control microbiologist in the pharmaceutical industry. She is particularly interested in studying the antimicrobial property found in food.

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