Single Cell Protein (SCP) Production PDF

Single cell protein  SCP refers to the dried microbial cells or total protein(MBP) extracted from pure microbial cell culture -monoculture – Algae, bacteria, filamentous fungi, yeasts, etc. Can be used as food supplement to humans (Food Grade) or animals (Feed grade). SCP contains high...

Single cell protein  SCP refers to the dried microbial cells or total protein(MBP) extracted from pure microbial cell culture -monoculture – Algae, bacteria, filamentous fungi, yeasts, etc. Can be used as food supplement to humans (Food Grade) or animals (Feed grade). SCP contains high protein content (60 – 80% of dry cell weight), fats, carbohydrates, nucleic acids, vitamins, and minerals. It is also rich in essential amino acids such as Lys and Met.  Single-Cell Protein (SCP) is a term coined at Massachusetts Institute of Technology by Prof C.L. Wilson (1966) and represents microbial cells (primary) grown in mass culture and harvested for use as protein sources in foods or animal feeds. Many scientists believe that single-cell protein production are possible solution to meet out the shortage of protein.  Single cell protein has the potential to be developed into a very large source of supplemental protein that could be used in livestock feeding. In some regions single cell protein could become the principal protein source that is used for domestic livestock, depending upon the population growth and the availability of plant feed protein sources.  Substrates microbes can be used to ferment some of the vast amounts of waste materials, straws; wood and wood processing wastes; food, cannery and food processing wastes; residues from alcohol production.  Sources of reduced carbon compounds that can be used for SCP production can be divided into- Certain C-compounds like methanol, ethanol can be made from either petroleum or renewable resources  Single Cell Protein SCP Process Regardless of the type of substrate or organism employed, the production of SCP involves following basic steps: (i) preparation of suitable medium with suitable carbon source; (ii) prevention of contamination of medium and the plant; (iii) production of the desired microorganism; (iv) separation of microbial biomass and its processing.  The medium for SCP production varies according to the micro organism. Among other things, the medium must contain a carbon source for cultivating the heterotrophic microorganisms, although green algae (Chlorella, Scenedesmus, Spirulina, etc.) can be cultivated autographically without a dissolved carbon source.  Commercial production of SCP The raw materials that can be used for single- cell protein manufacture include whey, sulphate waste liquors, hydrocarbon waste from the pet petroleum industry, and the vats used to produce alcoholic beverages. The production process involves growth of the organisms in large fermenting tanks with forced aeration for vigorous cell-growth.  Commercial Production of Single Cell from Hydrocarbons  Advantages of SCP Production (i) Microorganisms grow very vigorously and produce a high yield. It has been calculated that 100 lbs of yeast produces about 250 tons of protein within 24 hours. Algae grown in ponds produce 20 tons (dry weight) of protein per acre/year. The yield of protein is 10-15 times higher than soybeans and 20-50 times higher than corn. (ii) Industrial wastes or by-products are utilized as raw materials for microorganisms.  Advantages of SCP Production (iii) The protein content in the cells of microorganisms is reported to be very high 60% protein in dried cells of Pseudomonas spp; 40-50% in yeast cells and 20-40% in algal cells have been calculated. (iv) Yeasts grown in this process possess high vitamin content. (v) All essential amino acids are contained by single-cell proteins.  Disadvantages of SCP Production (i) Yeasts show lower growth rates, lower protein and lower methionine content. (ii) Moulds also have their limitations due to lower growth rates and lower protein content. (iii) Algae have cellulose in their cell walls which are not digestible. They also accumulate heavy metals which may prove harmful to living beings. iv) Since the bacterial cells are small in size and have low density, their harvesting from the fermented medium becomes difficult and costly.  Disadvantages of SCP Production (v) Bacterial cells possess high nucleic acid content which may prove detrimental to human beings by increasing the uric acid level in blood. Additional steps to overcome this problem make the production costly.  Some Examples of Single Cell Protein (SCP) from Microorganisms Grown on Different Substrates Organism Substrate Crude protein (%) Algae (Photosynthetic) CO2, Sunlight 55 Scenedesmus acutus Spirulina maxima CO2, HCO3, CO2, sunlight CO2, 62 Chlorella sp. cane syrup, molasses - Bacteria (Photosynthetic) Industrial wastes, sunlight 61 Rhodopseudomonas capsulata Bacteria (nonphotosynthetic) Bagasse 87 Cellulomonas sp. Methylococcus capsulatus Methane - Methylophilus methylotrophus Methanol 72 M. clara Methanol -  M. clara Methanol - Yeasts Candida sp. n-Alkenes 65 Candida utilis (Torula) Ethanol, Sulphite waste liquor 50-55 Kluyveromyces fragilis Cheese whey (lactose) 45-54 Saccharomyces cerevisiae Molasses 53 Fungi Fusarium graminearum Glucose - Cephalosporium eichhorniae Cassava starch 48-50 Chaetomium cellulolyticum Agriculture and forestry wastes 45 Paecilomyces varioti Sulphite waste liquor 55 Penicillium eye/opium Cheese whey (Iactose) 47 Scytalidium acidophthlum Acid, hydrolyzed waste paper 44-47 Gaseous hydrocarbons Methane is the most studied Major constituent of natural gas and is interesting Advantages: Available in high purity Leaves no residues and is easily removed High productivities and yield coefficients can be achieved Problems: 1. Needs to have two gases: methane and oxygen 2. Possible formation of inhibitory products in the medium 3. Potential explosive hazards with over 12% oxygen 4. Higher capital requirements to solve these problems 5. Only a few organisms ( probably only bacteria) can use methane Methanol: Can be obtained by chemical conversion of methane Can be obtained from other sources: coal, gas oil, wood etc Merits: Fully water soluble Few explosive hazards Range of microbes is greater: – Methylomonas methanolica – Pseudomonas utilis – Streptomyces sp – Candida boidinii – Torulopsis glabatra Ethanol Can be obtained from petroleum Merits: Same as methanol May even have a greater acceptability Can be used by certain bacteria, yeasts and fungi Renewable Carbon sources CO2 Can be only used by organisms with an independent energy yielding mechanism, as in photosynthesis CO is present in low concentration in atmosphere 2 Also possible to supply in an inexpensive form like combustion gas Alkaline lakes containing sodium bi carbonate can be used Algal pond systems can also be used, which allows efficient utilization of sunlight Arid and desert areas can be used Algae can be cultivated in seawater Dependence on climate invasion by herbivores, weeds and pathogens Molasses Main substrate for the traditional production of yeasts like Saccharomyceces cerevisiae and Candida utilis By product of cane and beet-sugar production May be expansive because of high demand in agriculture and in other fermentation industries Whey: Liquid by product in cheese manufacture, after removal of fat and casein from whole milk Origin of raw material makes it more acceptable Several SCP products are produced using Whey as raw material  Solid substrates Starchy or cellulosic materials Can be approached two different ways The solid material can be suspended in an aqeous medium Alternatively, solid state fermentation can be used Semi solid fermentation can be used Example: mushroom production Straw: Chinese or straw mushroom Composed straw: edible mushroom Wood Biomass recovery  Factors affecting Choice of Microorganism The key criteria used in selecting suitable strains for SCP production should consider the following: The substrates to be used as carbon energy and nitrogen source and the need for nutrient supplementation. High specific growth rates, productivity and yields on a given substrate. pH and temperature tolerance. Aeration requirements and foaming characteristics. Growth morphology in the reactor. Ease of recovery.  Factors affecting Choice of Microorganism Organisms should be stable genetically so that the strain with optimal biochemical and physiological characteristics may be maintained in the process through many hundreds of generations. Microorganisms involved in SCP production must be safe and acceptable for use in food. Safety and acceptability – non pathogenic, absence of toxins. Protein, RNA and nutritional composition of the product. Structural properties of the final product.  Fungi, Bacteria and Yeast In general, fungi have the capacity to degrade a wider range of complex plant materials, particularly plant polysaccharides. They can tolerate low pH which contributes to reducing fermenter infections. Growth of fungi as short, highly branched filaments rather than in pellets is essential in order to optimise growth rate.  Fungi, Bacteria and Yeast Bacteria, in general, have faster growth rates than fungi and grow at higher temperatures, thereby reducing fermenter cooling requirements. Bacterial and yeast fermentations are easier to aerate. In contrast to fungi, which are easily recovered by filtration, bacteria and yeast require the use of sedimentation techniques and centrifugation. Bacteria, in general produce a more favourable protein composition than yeast or fungi. Protein content in bacterial can range from 60- 65% Whereas fungi selected for biomass production and yeast have protein contents in the range of 33- 45%.  However, associated with the higher bacterial protein levels is a much higher level of nutritionally undesirable RNA content of 15-25%  Quorn Quorn is the leading brand of imitation meat mycoprotein in the United Kingdom. The mycoprotein used to produce Quorn is extracted from the fungus Fusarium venenatum, which is grown in large vats. The product was developed by Rank Hovis McDougall and Imperial Chemical Industries (ICI), and launched commercially as the Quorn brand as a joint venture of the two companies under the operating name of Marlow Foods.  Quorn Quorn is produced as both a cooking ingredient and a range of ready meals. It is sold largely in Europe, but also in other parts of the world as a health food and an alternative to meat; after changing production methods to ensure that only free-range eggs were used, the Vegetarian Society gave the product a seal of approval. Quorn  Nutritional and safety evaluations General considerations: First is a detailed chemical, physical and microbial characterization Chemical composition must be described by the content of protein, amino acids, lipids, vitamins, trace elements, Analysis of substrate residues and toxic substrates ( heavy metals, toxins etc) Physical properties Microbial data: species and strains used Data from tests for contaminants Biological evaluation: All nutritional and toxicological points need to be tested biologically Two questions: Safety for the animals Safety of the animal products for the human consumption All tested have to be done on target species, more than one species Rat is good choice for initial tests Target animals of different ages Effect on pregnant animals Please go through the link.. http://www.mycoprotein.org/ what_is_mycoprotein/ mycoprotein_story.html