SINGLE CELL PROTEIN AND BAKER’S YEAST
Rajesh G. Dobariya
shree M.&N. Virani Science College,
Single cell protein typically refers to source of mixed protein extracted from pure or mixed culture of algae, yeast, fungi or bacteria. The microbes which are used for single cell protein production must be non-pathogenic to plants, animals and man. Good nutritional value, easily and cheaply produced on scale, toxin free, fast growing, easily to separate from the medium and to dry. They have many silent feature. Biomass production is ordinarily carried out in continuous mode to maximize yields and economic scale. The raw material of this process is very cheap because we used molasses, whey, gas, oil etc. For a substrate. So SCP is waste to best. The molasses and various salts including ammonium and phosphate salt contain of the baker’s yeast. The yeast are used for the production of SCP. The baker’s yeast is useful to as and they create disadvantages also the SCP and baker’s yeast very useful for organism.
REFERENCE ID: PHARMATUTOR-ART-1885
Single cell protein(SCP) 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.
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 (frompaper manufacture), and similarly in 1941 employing Geotrichum.
"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 Refinery 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.
SCP 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 5%. 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.
Microbes employed include yeasts (Saccharomyces cerevisiae, Candida utilis=Torulopsis and Geotrichum candidum (=Oidium lactis)), other fungi (Aspergillus oryzae, 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 (i) low-cost aseptic conditions, (ii) avoiding over 100-fold dilution of the acidic hydrolysates to pH values needed for other microbes, and (iii) after the biomass is harvested, the acids can be reused.
Commercial production of SCP (Spirulina) includes Cyanotech in Hawaii and Earthrise in California.
Product Safety and Quality
Some contaminants can produce mycotoxins. Some bacterial SCP have amino acid 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.
Composition of Single Cell Proteins
–Yeast single-cell protein (SCP) is a high-nutrient feed substitute. This study evaluates the dual applications of a novel recombinant Pichia pastoris SMD1168H (SMD) yeast, expressing a tilapia vitellogenin protein (rVtg), as an SCP diet for Artemia and the first-feeding fish larvae. Instar II Artemia fed rVtg, rVtg precultured in 5% fish oil (rVtg-FO), Saccharomyces cerevisiae (SC), or native SMD had greater lipid contents (P < 0.05) than the freshly hatched. Lipid deposition in the Artemia fed rVtg or rVtg-FO was greater (P < 0.05) than in those fed SMD or SC. Diet-induced accumulation of low levels of docosahexaenoic acid [22:6(n-3)] was detected only in Artemia fed the rVtg-based diets. Tilapia (Oreochromis mossambicus) larvae were fed solely yeast diets singly or in combination (d 3–22), or a staggered regimen of yeast (d 3–12) followed by unenriched or yeast-enriched Artemia (d 13–22). The larvae fed rVtg for 22 d increased in length and weight (P < 0.05), whereas those fed SC or SMD suffered growth suppression and high mortality. Such adverse consequences were ameliorated when 50% of SC was substituted with rVtg. The larvae prefed rVtg followed by a dietary switch to Artemia preenriched for 48 h with rVtg or rVtg-FO were greatest in length, had the highest weight gain, and lived the longest. Besides delivering rVtg protein, essential fatty acids and amino acids, rVtg may have probiotic effects in enhancing larval survival.
ADVANTAGES OF SCP
- hold at 64C inactivates fungal proteases and allows RNases to hydrolyse RNA with release of nucleotides from cell to culture broth
- Large-scale production of microbial biomass has many advantages over the traditional methods for producing proteins for food or feed.
- 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)
- They can be easily genetically modified for varying the amino acid composition.
- A very high protein content 43-85 % in the dry mass.
- 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.
- Strains with high yield and good composition can be selected or produce relatively easily.
- Microbial biomass production occurs in continuous cultures and the quality is consistent since the growth is independent of seasonal and climatic variations.
- Land requirements is low and is ecologically beneficial.
- A high solar energy conversion efficiency per unit area.
- Solar energy conversion efficiency can be maximized and yield can be enhanced by easy regulation of physical and nutritional factors.
- Algal culture can be done in space which is normally unused and so there is no need to compete for land.
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