Download Food Microbiology-Single Cell Protein-UNIT-2-2012

1
SINGLE CELL PROTEIN
• Purified, dried microorganisms used as source of protein are called as single celled proteins.
• In olden days, the filamentous alga Spirulina was harvested in the lake Chad of Africa was consumed as food.
• During 1st world war Germans used Candida utilis in soups and sausages. It was extensively used during second
world war. It was produced in industrial scale in 1967.
Advantages of SCP
Among the overall advantages of SCP over plant and animal sources of proteins are the following22:
• Microorganisms have a very short generation time and can thus provide a rapid mass increase.
• Microorganisms can be easily modified genetically to produce cells that bring about desirable results.
• The protein content is high.
 The production of SCP can be based on raw materials readily available in large quantities.
 SCP production can be carried out in continuous culture and thus be independent of climatic changes.
• It has high protein and low fat content.
• It is good source of vitamins particularly B-complex. e.g. Mushrooms and Yeasts
• It can be produced through-out the year.
• Waste materials are used as substrate for the production of these proteins. It reduces the environmental pollution and
helps in recycling of materials.
• SCP organisms grow faster and produce large quantities of SCP from relatively small area of land and time.
• These have proteins with required aminoacids that can be easily selected by genetic engineering.
• During the production of SCP biomass, some organisms produce useful bye products such as organic acids and fats.
Sources of SCP
1. Algae:
• Chlorella, Scenedesmus acutus and Sprulina maxima are grown for SCP.
• These have about 60% protein with good amino acid composition but less in sulphur containing amino acids.
• Chlorella and Spirulina are used for commercial scale production in Thaiwan, Thailand, Japan, Israel, Mexico
and USA.
2
• It is spray dried and sold as pills and powders.
• Spirulina grown on sewage water is free of pathogenic microorganisms.
Disadvantages:
• These are not suitable for human consumption because they are rich in Chlorophyll. (Except Spirulina)
• It has low density i.e. 1-2 gm dry weight/litre of substrate.
• There is lot of risk of contamination during growth.
2. Yeasts and Fungi
• The filamentous fungi such as Chaetomium celluloliticum – grows on cellulose waste, Fusarium graminearum –grows on
starch and Paecilomyces varioti – grows on sulphur liquar are used for the production of SCP. These
have about 50 – 55 % protein.
• Yeasts such as Candida utilis (Torula yeast), Candida lipolytica – grow on Eathanol and Saccharomyces cervicea
– grows on Molasses are used for SCP production.
• Torula yeast as a food is obtained through fermentation using molasses as substrate. It has high protein –
carbohydrate ratio than forages. It is rich in lysine but poor in methionine and cysteine.
• Saccharomyces consists of high protein with good balance of amino acids and rich in B – complex vitamins. It is more
suitable as poultry feed.
• Several species of Mushrooms are used as protein rich food
Disadvantages:
• These have high nucleic acid content.
• Filamentous fungi show slow growth rate than yeasts and bacteria.
• There is contamination risk.
• Some strains produce mycotoxins and hence they should be screened.
3. Bacteria
• These have more than 80% protein. They are poor in sulphur containing amino acids.
• Brevibacterium uses hydrocarbons as substratum and Methylophilus methylitropous uses methanol.
• It has high nucleic acid content
Disadvantages:
3
• It has high RNA content.
• Risk of contamination is very high during the production process.
• Recovering the cells is a bit problematic.
• Endotoxin production should be carefully tested.
Single Cell Protein - SCP - SCP is the name given to a variety of microbial products, that are produced by
fermentation. When properly produced, this materials make satisfactory proteinaceous ingredients for animal feed
or human food. The production of protein from hydrocarbon wastes of the petroleum industry is the most recent
microbiological industry.
Yeast, fungi, bacteria, and algae are grown on hydrocarbon wastes, and cells are harvested as sources of protein. It
has been calculated that 100 lbs of yeast will produce 250 tons of proteins in 24 hours, whereas a 1000 lbs steer will
synthesize only 1 lb of protein 24 hours and this after consuming 12 to 20 lbs of plant proteins. Similar, algae
grown in ponds can produce 20 tons (dry weight) of protein, per acre, per year.
This yield is 10 to 15 times higher than soybean and 25 to 50 times higher than corn. There are both advantages and
disadvantages in using microorganisms for animal or human consumption. Bacteria are usually high in protein (50
to 80 percent) and have a rapid growth rate. The principal disadvantages are as follows:
1. Bacterial cells have small size and low density, which makes harvesting from the fermented medium difficult and
costly.
2. Bacterial cells have high nucleic acid content relative to yeast and fungi This can be detrimental to human beings,
tending to increase the uric acid level in blood. This may cause uric acid poising or gout. To decrease the nucleic acid
level additional processing step has to be introduced, and this increases the cost.
3. The general public thinking is that all bacteria are harmful and produce disease. An extensive education
programme is1required to remove this misconception and to make the public accept bacterial protein.
Yeasts have as advantages their larger size (easier to harvest), lower nucleic add content, high lysine content and
ability to grow at acid pH. However the most important advantage is familiarity and acceptability because of the
long history of its use in traditional fermentations. Disadvantages include lower growth rates, lower protein content
(45 to 65 per cent), and lower methionine content than in bacteria.
2. Filamentous fungi have advantages .in ease of harvesting, but have their limitations in lower growth rates,
lower protein content, and acceptability. Algae have disadvantages of having cellulosic cell walls which are
not digested by human beings. Secondly, they also concentrate heavy metals.
Single cell protein basically comprises proteins, fats carbohydrates, ash ingredients, water, and other
4
elements such as phosphorus and Potassium. The composition depends upon the organism and the substrate
which it grows. some typical compositions which are compared with soymeal and fish meal. If SCP is to be
used successfully, there are five main criteria to be satisfied;
1. The SCP must be safe to eat.
2. The nutritional value dependent on the amino acid composition must be high.
3. It must be acceptable to the general public.
4. It must have the functionality, i.e. characteristics, which are found in common staple foods.
5. The economic viability of the SCP process is extremely complex and is yet to be demonstrated
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.
&&&&&&&&&
SINGLE-CELL PROTEIN
The cultivation of unicellular microorganismsas a direct source of human food was suggested in the early 1900s.
The expression single-cell protein (SCP) was coined at the Massachusetts Institute of Technology around 1966 to
depict the idea of microorganisms as food sources.41 Although SCP is a misnomer in that proteins are not the only
food constituent represented by microbial cells, it obviates the need to refer to each product generically as in
"algal protein," "yeast cell protein," and so on.
Rationale for SCP Production
Among the overall advantages of SCP over plant and animal sources of proteins are the following 22:
• Microorganisms have a very short generation time and can thus provide a rapid mass increase.
• Microorganisms can be easily modified genetically to produce cells that bring about desirable results.
• The protein content is high.
 The production of SCP can be based on raw materials readily available in large quantities.
 SCP production can be carried out in continuous culture and thus be independent of climatic changes.