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.

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; essentialamino acids, represented by lysine and methionine; minerals;nucleic acidsandlipids.

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.

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 cerevisiaewas produced in Germany from molasses to replace protein.
• CandilaarboreaandC. utilis第二次世界大战期间使用。
• Similarly, during World War IICandida utiliswas used in soup and sausage.
• Many industries were established in the USA and Europe, especially forC. utilisproduction 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

S.N.	Microalgae	Bacteria	Fungi
1	They are phototrophic organisms.		They can be divided into unicellular yeast and mold.
2	They 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.
3	The advantages of using algae include simple cultivation, effective utilization of solar energy, faster growth, and high protein and	The advantages of using bacteria are its use of a wide range of substrates, their short time for generation, production of vitamins and micronutrients.	使用酵母的优点包括一个高的标准l 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%.
4	The 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%).
5	Examples:Tetraselmis suecica, Isochrysis galbana, Dunaliella tertiolecta, Chlorella stigmatophora, Spirulinaspp.	Examples:Mthylobacterium extorquens, Mrthylococcus capsulatus, Rhodobacter sphaeroides, and Afifella marina.	Examples: Yeast:Saccharomyces cerevisiae, kluyveromyces marxianus.Fungi:Aspergillus oryzae, Yarrowia lipolytica.

Fungiand substrates utilized by them and the protein content produced

S.N.	Substrate	Fungi	Protein content
1	Maltose, Glucose	Aspergillus fumigatus, Rhizopus chinensis
2	Cellulose, Hemicellulose	Aspergillus niger, A. oryzae, Cephalosporium eichhorniae, Chaetomium cellulolyticum
3	Glucose, Lactose, Galactose	Penicillium cyclopium
4
5	Hydrocarbons	Yarrowia lipolytica Candida tropicalis
6	Ethanol	Candida utilis
7	Methanol	Pichia spp.Pichia pastoris
8	Cellulose, Pentose	Scytalidium aciduphilium, Thricoderma viridae, Thricoderma alba
9	Glucose	Fusarium venenatum	44
10	Sulphite waste liquor	Paecilomyces varioti Candida utilis
11	Starch, Glucose	Fusarium graminearum
12	Starch	Saacharomycopsis fibuligera Candida utilis Saccharomyces cerevisiae
13	Whey
14	Banana waste Apple pomace Citrus pulp Potato starch processing waste Waste liquor	Aspergillus niger	18 17-20 25.6 38 50
15	Orange peel	Aspergillus niger Rhizopus oryzae Aspergillus niger Saccharomyces cerevisiae
16	Banana peel	Aspergillus terreus
17	Bergamot fruit (citrus fruit) peel	Penicillium roqueforti, Penicillium camemberti
18	Banana peel, pineapple peel, papaya peel	Phanerochaete chrysosporium, Panus tigrinus Phanerochaete chrysosporium
19	Papaya waste, cucumber peelings, pomegranate fruit rind, pineapple fruit skin, and watermelon skin	Rhizopus oligosporus
20	Orange peel	Trichoderma viride, Trichoderma reesei
21	Orange 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	38.5 49.3 53.4 39
22	切ese whey	Candida krusei	48
23	Whey and potato pulp	K. marxianus	33.7
24	Juice, pulp, and peel from oranges and lemons Corn stover effluent	R. opacus	42-52.7 47-52.7
25	Molasses Bagasse	Candida tropicalis	56 31
26	Rice bran	Cladosporium cladosporioides Penicillium citrinum Aspergillus flavus Aspergillus niger Aspergillus ochraceus Fusarium semitectum andsp1andsp2 Monascus ruber	10 10 10 11 10 10 9
27	Wheat straw	Pleurotus florida	63
28	Lignin	Chrysonilia sitophi	39
29	Rice bran (deoiled)	Aspergillus oryzae	24
30	切esy whey filter	Trichoderma harzianum	34
31	Citrus pulp	Trichoderma virideae	32
32	Waste capsicum powder Poultry litter 马铃薯淀粉工业浪费 Potato wastewater	Candida utilis	29 48 46 49
33	Spoiled date palm fruit	Hanseniaspora uvarum Zygosaccharomyces rouxi	49 49
34	切ese whey Orange pulp, molasses, brewer’s spent grain, whey, potato pulp, malt spent	Kefirspp.	54 23
35	Brewery’s spent grains (hemicellulosic hydrolysate)	Debaryomyces hansenii	32
36	Liquid sucrose	Hansenula jadinii
37	切ese whey Orange pulp, molasses, brewer’s spent grain, whey, potato pulp	Kluyveromyces marxianus	43 34
38	Inulin, crude oil, glycerol waste hydrocarbons	Yarrowia lipolytica	48-54

Algaeand substrates utilized by them and the protein content produced

S.N.	Substrate	Algae	Protein content
1		Anabaena cylindrica	43-56
2		Aphanizomenon flosaquae	62
3		Arthrospira maxima	56-77
4		Chlorella ellipsoidea	42.2
5		Chlorella ovalis	10.97
6		Chlorella pyrenoidosa	57
7		Chlorella spaerckii	6.87
8		Chlorella vulgaris	51-58
9		Dunaliella primolecta	12.26
10		Dunaliella salina	57
11		Dunaliella tertiolecta	11.4
12		Porphyridium aerugeneum	31.6
13		Porphyridium cruentum	28-39
14		Scenedesmus almeriensis	41.8
15		Scenedesmus obliquus	50-55
16		Spirulina platensis	60-71
17		Tetraselmis	36
18		Tetraselmis chuii	31-46.5
19	Soda ash effluent	Chaetomorpha antennina Ulva fasciata Chlorella	14-18.2 13.7-18.6
20	Tofu waste Tempeh waste 切ese waste	Chlorella spp.	52.32 52 15.43
21	Saline sewage effluents	Chlorella salina	51
22	Natural habitat	Gracilaria domingensis Gracilaria birdiae Laurencia filiformis Laurencia intricate Chondrus crispus Porphyra umbilicalis Gracilaria verrucosa	6.2 7.1 18.3 4.6 20.1 15-37 7-23
23	Wastewater	Chlorella sorokiniana Scenedesmus obliquus	45 52
24	Salinated water Desalinated water	Spirulina	48.59 56.17
25	CO2 and sunlight	Chlorella pyrenoidosa Scenedesmus quadricauda Spirulina maxima	53
26	n-Alkanes, kerosene	Candida intermedia, C. lipolytica, C. tropicalis, Nocardia spp
27		Nannochloropsis spp.	39.3
28		Nannochloropsis gaditana	39.3
29		Desmodesmus spp	37.3
30		Schizochytrium spp	9.4-42.5
31		Chlorella vulgaris	17.9
32		Scenedesmus spp	48

Bacteriaand substrates utilized by them and the protein content produced

S.N.	Substrate	Bacteria	Protein content
1	Orange wastes, lemon wastes	Rhodococcus opacus
2	Commercial shrimp feed	Afifella marinaSTW181	>46
3	Ram horn	Bacillus cereus Bacillus subtilis Escherichia coli	68 71 66
4	Potato starch processing waste	Bacillus licheniformis Bacillus pumilis	38 46
5	Soybean hull	Bacillus subtilis spp	26
6	Collagen meat packing waste in a fermenter	Bacillus megaterium
7	Glucose, fructose	Corynebacterium ammoniagenes	61
8	Cellulose	Cellulomonas spp Alcaligenes spp
9	Whey	Lactobacillus bulgaricus Candida krusei
10	Synthetic growth medium	Cupriavidus necator Rhodopseudomonas spp. Rhodobacter capsulatus Rhodopseudomonas acidophila	40-46 11 45 23
11	Petrochemical wastewater	Haloarcula sp. IRU1	76
12	甲烷(natural gas)	Methylococcus capsulatus, Ralstonia sp., Brevibacillus agri	67-73
13	Gas and liquid products of sewage	Methylomonas and Methylophilus	<41
14	Methanol	Methylophilus methylotrophus Methylomonas clara	81
15	甲烷	Methylomonas spp. (Methanomonas) Methylococcus capsuiatus Trichoderma spp.
16	Ethanol	Acinetobacter calcoaceticus
17	Diesel oil in fermenter	Achromobacter delvacvate
18	Supernatant and biogas	Methylophilus spp	24
19	Natural gas	Methilomonas.spp	69.3
20	Brewery wastewater	Rhizospheric diazotrophs	>55
21	Wastewater from a latex rubber	Rhodopseudomonas blastica	66.7
22	Sludge and sago starch processing	Rhodopseudomonas palustris	72-74
23	Poultry slaughterhouse wastewater	Rhodocyclus gelatinosus	67.6
24	Pineapple waste	Rhodobacter sphaeroides P47	66.6
25	Fermented pineapple extract	Rhodopseudomon as palustris P1	65
26	Soyabean wastewater	Rhodobacter sphaeroides Z08	52
27	Glutamate malate medium	Rhodovulvum sulphidophilum	15.6
28	Pig farm waste	Rhodocyclus gelatinosus	50.6
29	Sugar refinery wastewater	Rhodopseudomonas and R. fulvum	58
30	Miso-like effluent medium	Rhodocyclus gelatinosus	63
31	Dehydrated medium from pineapple peel waste	Rhodobacter sphaeroides P47	66.6
32	Seafood processing wastewater	Rhodocyclus gelatinosus	50
33	Wastewater from noodle	Rhodopseudomonas palustris	50
34	Municipal wastewater	Rhodopseudomonas spp. CSK01	60.1
35	Tuna condensate	Rhodocyclusg elatinosus R7	56
36	Cassava waste	Rhodocyclus gelatinosus	45
37	Simulated wastewater	Rhodopseudomonas palustris	45
	Photosythetic sludge	Rhodopseudomonas palustris	74

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.

2. 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.

3. 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.

4. Post-harvest treatment

• The harvested microbial cells are then dried to preserve them and reduce their volume, making them easier to store and transport.

5. SCP processing for food

• The dried cells are then processed to remove impurities, improve their nutritional content, and enhance their flavor and texture.

Advantages of Single Cell Protein

微生物通常用于生产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. SCP的生产是一个复杂的过程,再保险quires 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.

References

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