Single cell protein (SCP) shows very attractive features as a nutrient supplement for animals. It basically comprises of protein, carbohydrate, fats, water and elements like phosphorous and potassium and essential amino acids. SCP has various benefits over animal and plant proteins in that its requirement for growth are neither seasonal nor climatic dependent therefore it can be produced all-round the year. It can be grown on waste and is therefore environment friendly.
Priyanka Bhandari¹*, Manas Arora¹, Shriya Bhatt¹, Mohit Bharadwaj² Anshu Rahal³
¹M.V. Sc Scholar, ²PhD Scholar and ³Associate Professor
Department of Animal Nutrition, College of Veterinary and Animal Sciences, GBPUAT, Pantnagar, U.S Nagar, Uttarakhand- 263145
The world population is continuously increasing with increasing rate. By 2050, the world population could increase to 9.4 billion which at current consumption levels would cause the global demand for animal-derivative protein to reach 1250 million tons per year. According to some studies, the population increase will also be accompanied by economic progress, and due to which the increase in the living standard of about 3 billion people that subsequently increase the demands of food and water as well as there will be increasing demand of good quality food.
Globally the problem of malnutrition is increasing rapidly in developing countries as the population is increasing with an upright pyramid, which shows the increasing population of young and those required good quality of food. The competition for the good quality food with human, the animals also suffer a lot as the high yielders also require good quality of protein to produce good quality products. As the population of humans is increasing, the load on production of good quality food to meet the demand also increases and this puts a burden on the environment and also on the economy. The limited land is the problem and production is affected by several reasons. Therefore, the production of single cell proteins is promising way to tackle protein deficiency problem worldwide.
Single cell proteins (SCPs) or microbial proteins are the dead dried cells of microorganisms or purified protein isolated from microorganism’s cell culture and used in animals feed as fattening poultry, calves, pigs, and fish. It also has applications in leather and paper industry. SCPs have nearly 60 to 80% protein content in them on dry matter basis. SPCs contain high quantity of essential amino acid like methionine and lysine. Conventional substrates like starch, fruit, molasses and fruit waste and unconventional substrates like petroleum by products, ethanol, natural gas, lignocellulosic biomass and methanol have been used for SCPs production.
The microbial protein can be provided through the cultivation of various microbes and algae, which contain more than 30% protein in their biomass and which can provide a healthy balance of essential amino acids. Microbial protein is generally referred to as single cell protein (SCP), although some of the producing microbes, such as filamentous fungi or filamentous algae, may be multicellular. High growth rates or ability to utilize unique substrates, such as CO2 or methane, result in processes which offer much higher efficiency and/or sustainability than it is possible from traditional agriculture.
Microbial protein utilizes waste or raw materials and microorganisms on large scale, convert substrate with high efficiency, increasing microbial growth that results in good productivity. Also, seasonal factors have no effect on effectiveness of process. SCP products contain high quantity of nucleic acid (6-10%) that increases uric acid level in serum. This access in quantity results in precipitation of uric acid which can cause health problems i.e. formation of gout and kidney stone. The recommended dose of SCP supplemented to human or animal diet should have nucleic acid contents below 2%.
SCPs are used in animal diet like in the diet of fattening calves, pigs, broilers, as laying hens feed, fish breeding and feeding of pet. This is also used in foodstuffs as emulsifying agent, carrier of vitamins and scents, in soups, baked items as nutritional supplement, readymade meals and food recipes and have also applications in leather and paper processing and in foam stabilizing agent industry. Medicinal uses of Spirulina enhance antiviral and anticancer activity, improve and strengthen immune system. SCP production is a good way to overcome environmental pollution by utilizing waste materials. It is an efficient tool to transform agricultural waste such as rice hulls, rice straw, starchy residues and manure as a substrate into useful products.
MICROORGANISMS FOR SINGLE CELL PROTEIN (SCP)
PRODUCTION SINGLE CELL PROTEIN (SCP)-YEAST
There are several different sources of SCP and one of them is yeast, i.e. single cell fungi. Yeast is a good source of SCP. Nowadays, it is frequently used in animal feed as food supplements (dog and fish feed) and used as seasoning food in vegetarian diet. Yeast cell is larger than bacterial cell, can easily harvest, have high lysine and malic acid contents and low nucleic acid contents. Yeast cells have capability to grow on acidic pH. Yeast has low growth rate, low methionine and protein content (45-65%) as compared to bacteria. Yeast is also a good source for SCP production due to its superior nutritional quality. A variety of substrates and microbes are used for SCP production but necessary factor to consider before use of SCP is to check toxic and carcinogenic compounds, produced by microbe or by substrate and synthesized during production process. Two main limiting factors of yeast are high nucleic acid contents and low cell wall digestibility.
SINGLE CELL PROTEIN (SCP)-BACTERIA
Methylotrophic bacterium Methylophilusm ethylotrophus has about two hours generation time and is used in animal feed, producing good protein composition than other microbes. The characteristics of bacteria that make it suitable for SCP production include their short generation time and rapid growth with high protein content (50-80%). Photosynthetic Purple Non-Sulphur Bacteria (PNSB) contains 70-72% protein, highly resistant to toxicants and their protein compositions of necessary amino acids are similar to soybean protein. Its biomass is very useful in fish feed and rich in protein. Ammonia, urea, ammonium salts, organic nitrogen and nitrates in wastes are good source of nitrogen for bacteria and have capability to grow on different raw materials. Bacteria have high nucleic acid contents while less quantity of sulphur containing amino acids. The culture of bacteria has high risk of contamination and cell recovery is difficult. Bacterial culture medium requires mineral nutrient supplement to furnish nutrients. The selections of microbial strain for production of SCPs are based on the following criteria:
• Heat generation, oxygen requirements during fermentation process and foam character,
• Performance like growth rate, yield, heat and pH tolerance,
• Genetic stability during fermentation process and growth morphology,
• Their end product composition and structure in terms of protein,
• Have easy recovery and purification of their yield.
Bacteria have small cell size and low density, difficult to harvest in fermented medium, have high nucleic acid contents, and general perception of public that bacteria are harmful, awareness required to remove misconception about bacterial protein.
GENETICALLY MODIFIED ORGANISMS IN SCP PRODUCTION—FUTURE POSSIBILITIES
Use of genetically modified organisms (GMO) in food and feed got acceptance elsewhere in the world. As data regarding GMO consumption accumulates, they may gain further acceptance as protein sources become scarcer, particularly if a market develops for healthy or personalized nutrition. GMO yeast from bioethanol factories can already be used as cattle feed in some countries. Use of genetic elements from the host itself (self-clones) often means that no foreign DNA is introduced.
NUTRITIONAL ADVANTAGES OF SCP
Single cell protein basically comprises proteins, fats carbohydrates, ash ingredients, water, and other elements such as phosphorus and potassium. Aside from the nutritional benefits of single cell protein, another benefit of single cell protein technology is their throughout the year production. Also it plays its role in waste management as waste materials are used as substrate. Small area of land is required and SCP is made in less time. To access nutritional value of single cell protein, many factors must be considered which include nutrient composition, amino acid profile, vitamin and NA content as well as allergies and gastrointestinal effects.
CONCLUSION
In conclusion, SCP shows very attractive features as a nutrient supplement for animals. It basically comprises of protein, carbohydrate, fats, water and elements like phosphorous and potassium and essential amino acids. SCP has various benefits over animal and plant proteins in that its requirement for growth are neither seasonal nor climatic dependent therefore it can be produced all-round the year. SCP has high protein content with wide amino acid spectrum, low fat content and higher protein carbohydrate ratio than forages. It can be grown on waste and is therefore environment friendly. Thus, the use of SCP as an alternative nutrient supplement can solve the problem of food scarcity of rapidly growing population especially in a developing country like India. However, despite of all these benefits SCP production has gained less importance because of lack of acceptability of SCP as a nutrient supplement among people. Moreover, high nucleic acid content, presence of non-digestible cell wall, unacceptable colours and flavours and a high risk of contamination and cell recovery further restrict their use as a global food. Therefore, efforts should be made to find alternative substrates and methods which can minimize the pitfalls of the substrates and methods currently in use for the production of SCP and thus lead to acceptance of this valuable nutrient supplement on a global basis.
References
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