ARTICLE 64 FEED & ADDITIVE MAGAZINE July 2022 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 (5080%). 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. Figure 1. Spirulina Powder
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