One of the interesting Biology Topics is the study of animal behavior and how it is influenced by genetics and the environment.
Production of Single Cell Protein (SCP) from different Microorganisms as a Protein Supplement for Human and Animal Feed
Single-cell protein (SCP) refers to protein obtained from the large-scale growth of microorganisms such as bacteria, yeast, and other fungi and algae. The term SCP was given at the Massachusetts Institute of Technology by some scientists in 1966. At present the term refers to not only the isolated cell protein but also to any microbial biomass used as food or feed additives. The cells from the various microorganisms, like bacteria, fungi, and several filamentous algae, are used as food by treating them in various ways. These are called single-cell proteins (SCP).
During the last two decades, there has been growing interest in using microbes for food production, in particular for feeding domesticated food-producing animals such as poultry. It has been assumed that the use of SCP derived from low-value waste materials would improve human nutrition. Many groups of microorganisms are used as sources of protein. Some of the microorganisms used as sources of SCP with their protein content or listed in the table.
SCP Produced by Different Microorganisms:
|Microorganisms||Protein (% 100gm, on dry weight basis)|
|Candida lipolytica||65 – 69|
|Agaricus campestris||36 – 45|
Microorganisms produce protein much more efficiently than any farm animal. However, the cow also has the unique ability to convert grass into protein-rich milk. The cow has been described as “a live, self-reproducing and edible bioreactor”. The advantages of using microbes for SCP production are:
- Microorganisms can grow at remarkably rapid rates under optimum conditions.
- Microorganisms are more easily modified genetically than plants and animals.
- They can be more easily subjected to gene transfer technology.
- They have relatively high protein content and the nutritional value of protein is good.
- They can be grown in a small continuous fermentation process and growth is independent of climate.
- They can grow on a wide range of raw materials like low-value wastes and plant-derived cellulose.
Production Process of SCP
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, floatation, precipitation, coagulation, and filtration or the use of semi-permeable membranes.
The single-cell protein must 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 the dewatering process require equipment that is expensive and not always suitable for small-scale operations. It is economically prudent to feed the product locally and soon after it is produced.
Microorganisms and Substrate used in the production of SCP the mentioned in the table below:
|Bacillus megaterium||Non-proteinaceous N2 compound|
|Bacillus subtilis||Cellulose, hemicellulose|
|Lactobacillus sp.||Glucose, maltose|
|Aspergillus fumigatus||Maltose, Glucose|
|Aspergillus niger||Cellulose, hemicellulose|
|Penicillium cyclopium||Lactose, galactose|
|Saccharomyces cerevisiae||Pentose, maltose|
|Candida tropicalis||Maltose, Glucose|
|Chlorella pyrenoidosa||Photosynthetic CO2|
|Spirulina sp.||Photosynthetic CO2|
Disadvantages of SCP
- Some microorganisms produce toxic substances. Such organisms when taken in, lead to indigestion and allergies.
- The high nucleic acid content in many microbial biomass is also not desirable.
SCP from Mushroom
Mushrooms are the members of higher fungi, belonging to the class Ascomycetes (e.g., Morchella, Tuber, etc.) and Basidiomycetes. (e.g., Agaricus, Volvariella, Pleurotus, Auricularia etc.). The fruiting bodies of these fungi have acquired importance since these are considered to be delicious food for human beings. Generally mushroom contains 85-90% water of their dry matter. However, the amount of water is greatly influenced by relative humidity and temperature during growth and storage. Protein is the most critical component which contributes a lot to the nutritional value of food.
The amount of protein varies from 34-44% of total dry weight in Agaricus sp. Besides protein, a large variety of free and combined fatty acids also occur in A. bisporus with high concentrations of palmitic acid, stearic acid, and oleic acid. Fresh mushroom contains a relatively large amount of carbohydrates i.e., 3-28%, particularly pentoses, hexoses, disaccharides, and trehalose (a mushroom sugar). They are also a good source of several vitamins (thiamin, riboflavin,; niacin, biotin, ascorbic acid, vitamins A, B, C, D), minerals (sodium, potassium, calcium, iron, etc.) and essential amino acids (methionine, citrulline, ornithine, etc.).
SCP from Algae
Algae such as Chlorella and Scenedesmus have long been used as food in Japan, while Spirulina is widely used in Africa and Mexico. Chlorella is used as a protein and vitamin supplement in some Japanese yogurts, ice cream, and breads. In some parts of the world, algae are grown in ponds to aid in the removal of organic pollution and the resultant biomass is harvested, dried and the powder added to animal feed. In India at Central Food Technology Research Institute (CFTRI), Mysore, research is being conducted on the use of blue-green alga, Spirulina as a supplement to diet (food and feed). The alga is cultured, dried, powdered, and then used in the form of one-gram tablets. When fish and children (3-12 years) were fed on this, encouraging results were obtained. Mass cultivation of Spirulina offers several advantages over Chlorella and Scenedesmus which are as follows.
- Spirulina, being a filamentous alga can be harvested by single and less expensive methods such as nylon or cotton cloth filter.
- Filaments float on the water surface due to the presence of gas vacuoles. Hence, there is no problem of harvesting, unlike Chlorella and Scenedesmus.
- There is the least chance of contamination in the growth tanks of Spirulina as it grows at a high alkaline pH of 8-11.
- Heat drying is sufficient for Spirulina as it has a thin cell wall.
- Research on several aspects of possible adverse changes in multigeneration feeding tests on laboratory animals and humans has shown no adverse effects.
- Spirulina is highly digestive (85-90%) due to its thin wall and low nucleic acid contents (4%). it contains a high percentage of digestible proteins (62-72%), vitamins, amino acids, and other nutrients.
- SCP is rich in high-quality protein and has less amount of fat content. The SCP can be produced in the laboratory throughout the year and it also helps to reduce environmental pollution.
Composition of Multin (i.e., dried powder of Spirulina fusiformis) (Constituents are in per 100g of powder) Analysed Michelson Laboratories Inc California, USA (1988):
Single-cell protein (SCP) is rich in protein and can be stored and transported over long distances. It is mainly used as animal fodder and also replaces other protein-rich materials, such as Soyabean meal or fish meal. SCP-Production and utilization processes do not create imbalance in a natural ecosystem. Single-cell protein typically refers to proteins extracted from pure culture or mixed culture of microorganisms.