Single cell protein
Encyclopedia
Single-cell protein typically refers to sources of mixed protein
extracted from pure or mixed cultures of algae
, yeasts, fungi or bacteria
(grown on agricultural wastes) used as a substitute for protein-rich foods, in human and animal feeds.
In 1919 Endomyces vernalis yielded fats from sulphite liquor (from paper manufacture), and similarly in 1941 employing Geotrichum
.
in Britain, was authorized.
The term SCP was coined in 1966 by Carol L. Wilson at MIT.
The "food from oil" idea became quite popular by the 1970s, with Champagnat being awarded the UNESCO Science Prize
in 1976, and paraffin-fed yeast facilities being built in a number of countries. The primary use of the product was as poultry and cattle feed.
The Soviets
were particularly enthusiastic, 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 of this kind by 1989, when, pressured by the environmentalist movements, the government decided to close them down, or convert to some other microbiological processes.
. Engineers have developed ways to increase the concentrations including centrifugation, flotation, precipitation, coagulation and filtration, or the use of semi-permeable membranes.
The single cell protein needs to be dehydrated to approximately 10% moisture content and/or acidified to aid in storage and prevent spoilage. The methods to increase the concentrations to adequate levels, and de-watering process require equipment that is expensive and not always suitable for small-scale operations. It is economically prudent to feed the product locally and shortly after it is produced.
, Pichia pastoris
, Candida utilis=Torulopsis and Geotrichum candidum
(=Oidium lactis)), other fungi (Aspergillus oryzae
, Fusarium venenatum
, Sclerotium rolfsii, Polyporus
and Trichoderma
), bacteria (Rhodopseudomonas capsulata). and algae (Chlorella
and Spirulina
). Typical yields of 43 to 56%, with protein contents of 44% to 60%.
The fungus Scytalidium acidophilum grows at below pH 1, offering advantages of:
profiles different from animal proteins. Yeast and fungal proteins tend to be deficient in methionine
.
Microbial biomass has a high nucleic acid
content,and levels need to be limited in the diets of monogastric
animals to <50g per day. Ingestion of purine
compounds arising from RNA
breakdown, leads to increased plasma
levels of uric acid
, which can cause gout
and kidney stones. Uric acid can be converted to allantoin
, which is excreted in urine. Nucleic acid removal is not necessary from animal feeds but is from human foods. A temperature hold at 64°C inactivates fungal protease
s and allows RNases to hydrolyse RNA with release of nucleotide
s from cell to culture broth.
1. Microorganisms have a high rate of multiplication to hence rapid succession of generation (algae: 2–6 hours, yeast: 1–3 hours, bacteria: 0.5-2 hours)
2. They can be easily genetically modified for varying the amino acid composition.
3. A very high protein content 43–85 % in the dry mass.
4. They can utilize a broad spectrum of raw materials as carbon sources, which include even waste products. Thus they help in the removal of pollutants also.
5. Strains with high yield and good composition can be selected or produce relatively easily.
6. Microbial biomass production occurs in continuous cultures and the quality is consistent since the growth is independent of seasonal and climatic variations.
7. Land requirements is low and is ecologically beneficial.
8. A high solar energy conversion efficiency per unit area.
9. Solar energy conversion efficiency can be maximized and yield can be enhanced by easy regulation of physical and nutritional factors.
10. Algal culture can be done in space which is normally unused and so there is no need to compete for land.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
extracted from pure or mixed cultures of algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
, yeasts, fungi or bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
(grown on agricultural wastes) used as a substitute for protein-rich foods, in human and animal feeds.
Early history
Since 2500 BC yeasts have been used in bread and beverage production. In 1781 processes for preparing highly concentrated forms of yeast were established.In 1919 Endomyces vernalis yielded fats from sulphite liquor (from paper manufacture), and similarly in 1941 employing Geotrichum
Geotrichum
Geotrichum is a genus of fungi found worldwide in soil, water, air, and sewage, as well as in plants, cereals, and dairy products; it is also commonly found in normal human flora and is isolated from sputum and feces....
.
"Food from oil"
In the 1960s, researchers at British Petroleum developed what they called "proteins-from-oil process": a technology for producing single cell protein by yeast fed by waxy n-paraffins, a product produced by oil refineries. Initial research work was done by Alfred Champagnat at BP's Lavera Oil Refinery in France; a small pilot plant there started operations in March in 1963, and the same construction of the second pilot plant, at Grangemouth Oil RefineryGrangemouth Refinery
Grangemouth refinery is a mature complex oil refinery located on the Firth of Forth in Grangemouth, Scotland.Currently operated by Ineos, it is Scotland's only oil refinery , and is also the UK's second-oldest; it supplies refined products to customers in Scotland, northern England, Northern...
in Britain, was authorized.
The term SCP was coined in 1966 by Carol L. Wilson at MIT.
The "food from oil" idea became quite popular by the 1970s, with Champagnat being awarded the UNESCO Science Prize
UNESCO Science Prize
The UNESCO Science Prize is a biennial scientific prize awarded by the United Nations Educational, Scientific and Cultural Organization to "a person or group of persons for an outstanding contribution they have made to the technological development of a developing member state or region through...
in 1976, and paraffin-fed yeast facilities being built in a number of countries. The primary use of the product was as poultry and cattle feed.
The Soviets
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
were particularly enthusiastic, opening large "BVK" (belkovo-vitaminny kontsentrat, i.e., "protein-vitamin concentrate") plants next to their oil refineries in Kstovo
Kstovo
Kstovo is a town and the administrative center of Kstovsky District of Nizhny Novgorod Oblast, Russia, located on the right bank of the Volga River, southeast of Nizhny Novgorod. Population: -History:...
(1973) and Kirishi
Kirishi
Kirishi is a town in Leningrad Oblast, Russia, situated on the right bank of the Volkhov River, southeast of St. Petersburg. Population: -History:...
(1974). The Soviet Ministry of Microbiological Industry had eight plants of this kind by 1989, when, pressured by the environmentalist movements, the government decided to close them down, or convert to some other microbiological processes.
Production Process
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). The problem with extracting single cell proteins from the wastes is the dilution and cost. They are found in very low concentrations, usually less than. Engineers have developed ways to increase the concentrations including centrifugation, flotation, precipitation, coagulation and filtration, or the use of semi-permeable membranes.The single cell protein needs to be dehydrated to approximately 10% moisture content and/or acidified to aid in storage and prevent spoilage. The methods to increase the concentrations to adequate levels, and de-watering process require equipment that is expensive and not always suitable for small-scale operations. It is economically prudent to feed the product locally and shortly after it is produced.
Examples
Microbes employed include yeasts (Saccharomyces cerevisiaeSaccharomyces cerevisiae
Saccharomyces cerevisiae is a species of yeast. It is perhaps the most useful yeast, having been instrumental to baking and brewing since ancient times. It is believed that it was originally isolated from the skin of grapes...
, Pichia pastoris
Pichia pastoris
Pichia pastoris is a species of methylotrophic yeast. Pichia is widely used for protein expression using recombinant DNA techniques. Hence it is used in biochemical and genetic research in academia and the biotechnical industry....
, Candida utilis=Torulopsis and Geotrichum candidum
Geotrichum candidum
Geotrichum candidum is a Fungi or mold that can act as a plant pathogen causing sour rot on peach, nectarine, tomato and carrot. It is also widely used in the production of many dairy products including many natural rind cheeses such as Camembert and other bloomy rind cheese, Saint-Nectaire, Tomme...
(=Oidium lactis)), other fungi (Aspergillus oryzae
Aspergillus oryzae
Aspergillus oryzae is a filamentous fungus . It is used in Chinese and Japanese cuisine to ferment soybeans. It is also used to saccharify rice, other grains, and potatoes in the making of alcoholic beverages such as huangjiu, sake, and shōchū...
, Fusarium venenatum
Fusarium venenatum
Fusarium venenatum is a microfungus of the genus Fusarium that has a high protein content. One of its strains is used commercially for the production of the single cell protein mycoprotein....
, Sclerotium rolfsii, Polyporus
Polyporus
Polyporus is a genus of fungi in the Polyporaceae family. It is a genus used for the production of single cell proteins, sources of mixed protein extracted from pure or mixed cultures of algae, yeasts, fungi or bacteria used as a substitute for protein-rich foods, in human and animal feeds.The...
and Trichoderma
Trichoderma
Trichoderma is a genus of fungi that is present in all soils, where they are the most prevalent culturable fungi. Many species in this genus can be characterized as opportunistic avirulent plant symbionts.-Species:...
), bacteria (Rhodopseudomonas capsulata). and algae (Chlorella
Chlorella
Chlorella is a genus of single-celled green algae, belonging to the phylum Chlorophyta. It is spherical in shape, about 2 to 10 μm in diameter, and is without flagella. Chlorella contains the green photosynthetic pigments chlorophyll-a and -b in its chloroplast...
and Spirulina
Spirulina
Spirulina may refer to:* Spirulina , a health-food supplement* Spirulina , a cyanobacterium group* Ochthephila spirulina, species of gastropod in the Hygromiidae family...
). Typical yields of 43 to 56%, with protein contents of 44% to 60%.
The fungus Scytalidium acidophilum grows at below pH 1, offering advantages of:
- low-cost aseptic conditions,
- avoiding over 100-fold dilution of the acidic hydrolysates to pH values needed for other microbes
- after the biomass is harvested, the acids can be reused.
Product Safety and Quality
Some contaminants can produce mycotoxins. Some bacterial SCP have amino acidAmino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
profiles different from animal proteins. Yeast and fungal proteins tend to be deficient in methionine
Methionine
Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...
.
Microbial biomass has a high nucleic acid
Nucleic acid
Nucleic acids are biological molecules essential for life, and include DNA and RNA . Together with proteins, nucleic acids make up the most important macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information...
content,and levels need to be limited in the diets of monogastric
Monogastric
A monogastric organism has a simple single-chambered stomach, whereas ruminants have a four-chambered complex stomach. Examples of monogastric animals include omnivores such as humans, rats and pigs, carnivores such as dogs and cats, and herbivores such as Horses and rabbits. Herbivores with...
animals to <50g per day. Ingestion of purine
Purine
A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely distributed kind of nitrogen-containing heterocycle in nature....
compounds arising from RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
breakdown, leads to increased plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
levels of uric acid
Uric acid
Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates such as ammonium acid urate. Uric acid is created when the body breaks down purine nucleotides. High blood concentrations of uric acid...
, which can cause gout
Gout
Gout is a medical condition usually characterized by recurrent attacks of acute inflammatory arthritis—a red, tender, hot, swollen joint. The metatarsal-phalangeal joint at the base of the big toe is the most commonly affected . However, it may also present as tophi, kidney stones, or urate...
and kidney stones. Uric acid can be converted to allantoin
Allantoin
Allantoin is a chemical compound with formula C4H6N4O3. It is also called 5-ureidohydantoin or glyoxyldiureide. It is a diureide of glyoxylic acid....
, which is excreted in urine. Nucleic acid removal is not necessary from animal feeds but is from human foods. A temperature hold at 64°C inactivates fungal protease
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
s and allows RNases to hydrolyse RNA with release of nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
s from cell to culture broth.
Advantages of Production
Large-scale production of microbial biomass has many advantages over the traditional methods for producing proteins for food or feed.1. Microorganisms have a high rate of multiplication to hence rapid succession of generation (algae: 2–6 hours, yeast: 1–3 hours, bacteria: 0.5-2 hours)
2. They can be easily genetically modified for varying the amino acid composition.
3. A very high protein content 43–85 % in the dry mass.
4. They can utilize a broad spectrum of raw materials as carbon sources, which include even waste products. Thus they help in the removal of pollutants also.
5. Strains with high yield and good composition can be selected or produce relatively easily.
6. Microbial biomass production occurs in continuous cultures and the quality is consistent since the growth is independent of seasonal and climatic variations.
7. Land requirements is low and is ecologically beneficial.
8. A high solar energy conversion efficiency per unit area.
9. Solar energy conversion efficiency can be maximized and yield can be enhanced by easy regulation of physical and nutritional factors.
10. Algal culture can be done in space which is normally unused and so there is no need to compete for land.