Properties and Applications of Single Cell Protein from Microorganisms
Simran, Reena Rajkumari B*
School of Biosciences and Technology, Vellore Institute of Technology, Vellore.
*Corresponding Author E-mail: b.reenarajkumari@vit.ac.in
ABSTRACT:
Food crisis is a major issue in underdeveloped and overpopulated countries. Due to this crisis, many people are prone to get affected by various health disorders and nutrition relation problems. The protein sources for vegetarians are very limited. Due to globalization, there is a change of lifestyles, and there is an increase in consumption of junk food. Consequently, there is a rise in the number of obese people. Protein supplements are expensive and not easily affordable for everyone. Hence, there arises a need for a protein source, which is consumed by everyone and has high nutritive value too. With the ever-increasing rise in pollution, the quality of food and vegetation is falling. Maybe due to globalization, the food choices are increasing, but the contamination and adulteration are rising too. Purity has become a major concern for people at present. To combat these problems, single cell protein from microorganism can be used as an optional nutritional source. This article talks about different microorganisms sources of single cell protein.
KEYWORDS: Single cell protein, Spirulina, Micro-organism, Nutritional, Biomass.
INTRODUCTION:
Out of the three forms, Spirulina platensis is commonly used. As Spirulina has a high content of protein, it used as a human food supplement as well as for cattle feed. Besides its nutritive value, it provides other benefits like, it is rich in antioxidants, it aids the removal of synthetic dyes and used as a biofilm due to its metal binding capacity, also used for bioremediation. Thus, Spirulina has industrial applications as well as nutritive value.
Arthrospira (Spirulina) platensis has a relatively fragile cell wall, composed mainly of murein and no cellulose.1 Murein is also known as peptidoglycan, which is a polymer composed of sugars and amino acids. A. platensis does not have cytoplasm and chloroplast instead; it has thylakoids bundles circling the peripheral part of cytoplasm with their associated structures (phycobilisomes).1 Based on the optical mapping the genome structure of A. platensis estimates to be single, circular chromosome of 6.8Mb. By annotation, 6630 protein-coding genes, as well as 2 sets of rRNA genes and 40 tRNA genes, yielded.2
Chlorella vulgaris is one of those edible algae, which is widely used as food for animals as well as humans.3 It has a cell wall mainly composed of hemicelluloses and cellulose. Total proteins content in mature C. vulgaris is 42–58% of biomass dry weight and varies according to growth conditions. Proteins have multiple roles, and almost 20% of the total proteins are bound to the cell wall, more than 50% are internal, and 30% migrate in and out of the cell.3 Chlorella has a broad range of applications as biofuel, human nutrition, wastewater treatment, agrochemical, animal feed, etc.
Spirulina and Chlorella are reported contaminated with some toxins such as microcystins (MCs) which are harmful to the liver.4 Nucleic acid content in single cell protein is one of the major drawbacks as excessive intake leads to various health disorders such as gout formation or kidney problems due increase in uric acid.5 Yeast has been employed as food, since ancient times in various products like bread, etc. Most common yeast species are Candida, Hansenula, Pitchia, Torulopsis and Saccharomyces, which are widely used in single cell protein production.6 Yeast has low protein content (45-65%) and low methionine as compared to bacteria. They possess high lysine content and can grow at acidic pH.5,7
Filamentous fungi are employed to give us alternatives of meat protein in the form of mycoprotein.8 Fusariumvenenatum A3/5, is used for development of mycoprotein.9 It is intended as a protein source for humans. F. venenatummyco-protein contains approximately 44% (w/w) protein, on a dry weight basis. All essential amino acids are present, except the concentration of sulphur-containing amino acids which is relatively small. Mycoprotein also provides a source of dietary fiber as chitin and glucans from the mycelial walls, contains low cholesterol and is low in saturated fats [10]. Mycoprotein is sold under the trade name, Quorn. It is the only source of mycoprotein for human consumption, which is on the market today.9
Bacteria are most suitable for single cell protein production because of its rapid growth rate. It can grow on large varieties of substrates like sugars, hydrocarbons, petrochemicals, nitrogen sources and organic nitrogen, etc. Common bacteria involved in the production are Brevibacterium, Methylophilus methylitropous, Acromobacter delvaevate, Acinetobacter calcoacenticus, Aeromonas hydrophilla, Bacillus megaterium, Bacillus subtilis, Lactobacillus species, Cellulomonas species, Methylomonas methylotrophus, Pseudomonas fluorescens, Rhodopseudomonas capsulate, Flavobacterium species, and Thermomonospora fusca.6 It is usually high in protein content (50-80%). They have high nucleic acid content as compared to yeast and fungi, to decrease the content, additional processes are required which makes the production cost high. In addition bacteria are small in size with low density, which makes harvesting difficult.5
Spirulina:
Spirulina is a multicellular, filamentous cyanobacterium. It appears as blue-green filaments composed of cylindrical cells arranged in unbranched, helicoidaltrichomes under the microscope. The filaments are motile, gliding along their axis and heterocysts are absent.11 S.platensis and S.maxima have a granular cytoplasm containing gas vacuoles and easily visible septa.
In ancient times Spirulina was cultivated by people near Lake Chad in Africa and the Aztecs near Lake Texcoco in Mexico. It used as a food source by drying.12 Since it is dried, it utilizes solar energy, a renewable source of energy thus helping in achieving sustainability. Tribal communities use it as a source of protein due to its high growth rate. Its growth rate is low as compared to non-spirulina sources of protein. It uses light, carbon dioxide and inorganic samples as substrate. It is cultivated in ponds, bioreactors by maintaining a pH up to 11. It possesses high and severe contamination risks and has low S-containing amino acids. Spirulina has the highest protein of any natural food (65%); far more than animal and fish flesh (15-25%), soybeans (35%), dried milk (35%), peanuts (25%), eggs (12%), grains (8-14%) or whole milk (3%). Spirulina has limited levels of methionine and cysteine. In comparison to grains, seeds, vegetable spirulina is still had higher levels of methionine and cysteine and legumes, and higher in lysine than all vegetables except legumes.13 Spirulina has no cellulose in its cell walls, as it is composed of soft mucopolysaccharides, thus making it easily digested (85-90%) and assimilated. This easy digestibility is important for people suffering from intestinal malabsorption and older individuals who have difficulty digesting complex proteins, and are on restricted diets.
Only 5% fat content is present in Spirulina.10grams of Spirulina has 36 calories and 1.3mg cholesterol.13 Thus, it is a low-fat and low-calorie source of protein. Spirulina is the richest food in beta-carotene, ten times more concentrated than carrots. Ten grams of Spirulina provide 14mg of beta-carotene. High doses of Vitamin A may be toxic, but beta-carotene in Spirulina and vegetables is safe, as in humans beta-carotene is converted to Vitamin A as needed, as it is important in maintaining mucous membranes and pigments necessary for vision. Beta-carotene has therapeutic effects such as reducing serum cholesterol. Spirulina contains an antioxidant-rich complex of at least ten carotenoids. These mixed carotenes and xanthophylls function at different sites in the body and work synergistically with the other essential Vitamins (Vitamin E), minerals and phytonutrients in Spirulina. This is more effective than an isolated, synthetic beta-carotene supplement. Spirulina is the richest source of B-12, higher than beef liver, chlorella or vegetables. B-12 is necessary for the development of red blood cells, especially in the bone marrow and nervous system. Though B-12 deficiencies are quite rare, B-12 is the most difficult vitamin to get from plant sources, thus vegetarians have opted for Spirulina. The human body easily absorbs Spirulina iron. Its blue pigment, phycocyanin, forms soluble complexes with iron and other minerals during digestion making iron more bioavailable. Hence, iron in Spirulina is over twice absorbable than the form of iron found in vegetables and most meats.
Spirulina has several pharmacological activities such as anticancer, antiviral, antibacterial, metalloprotective, antioxidant and immunostimulant effects. It is a blue-green algae having strong antioxidant activity and provokes a free radical scavenging enzyme system.6 Mechanisms of anticancer, antiviral and antimicrobial effects of Spirulina are because of its content of endonuclease (which repair damaged DNA), calcium sulfated polysaccharide (which inhibits in vitro replication of viruses) and fatty acids (especially high content of gamma-linoleic acid), respectively. Furthermore, the metalloprotective role of Spirulina is due to the presence of beta-carotene, vitamins C and E, enzyme superoxide dismutase, selenium and brilliant blue polypeptide pigment phycocyanin.14 High molecular weight anionic polysaccharides isolated from Spirulina possess antiviral and immunomodulating activities. The protective effect of S.platensis against cadmium-induced oxidative stress could be maybe indirect through the enhancement of the activity of GSH peroxidase and superoxide dismutase (free radical scavengers) or direct by inhibiting peroxidation of lipid and scavenging of free radicals. These characteristics are due to the high concentration of antioxidant components present in S. platensis. Polysaccharides from Spirulina are capable of a variety of biological activities including antiviral activity against herpes simplex virus type 1 (HSV-1), inhibitory effects on corneal neovascularization, increased immune stimulatory activity and anticoagulant activity mediated by heparin cofactor II.15 An increased yield of crude polysaccharides observed when the solid-to-liquid ratio and extraction temperature raised. The optimum conditions for polysaccharide extraction from Spirulina sp. are as follows: a solid-to-liquid ratio of 1:45 (w/v), extraction temperature at 90 degree Celsius, extraction time of 120 min and a single extraction. Under these conditions, a crude polysaccharide yield of around 8.3% of dry weight comprising rhamnose as the major component is obtained.15
Spirulina, a cyanobacterium generally used as a dietary supplement, is amongst the most ‘nutritionally packed’ dietary supplement available. With respect to immunity, it moderates the production of cytokines by human peripheral blood mononuclear cells, not astounding given the rich content of flavonoids and sulfolipids. Spirulina products comprise bioactive proteins with the ability to stimulate the intestinal immune system to boost the responsiveness to vaccines and mend allergic rhinitis.
Spirulina is proficient of reducing inflammation and capable of exhibiting antioxidant effects. In a study conducted, it was postulated that Spirulina might amend anemia and immunosenescence in senior citizens with a history of anemia. Forty volunteers of both sexes with an age of 50 years or older who had no history of any major chronic diseases were enrolled. Partakers took a Spirulina supplementation for 12 weeks and were administered ample dietary questionnaires to determine their nutritional routine during the study. Complete cell count (CCC) and indoleamine 2, 3-dioxygenase (IDO) enzyme activity, as a sign of immune function, was determined at the reference point and weeks 6 and 12 of supplementation. Thirty study partakers completed the entire study, and the data obtained analyzed. Over the 12-week study period, there was a steady escalation in average values of mean corpuscular hemoglobin in subjects of both sexes. In addition, mean corpuscular volume and mean corpuscular hemoglobin concentration also increased in male partakers. Older women seemed to benefit faster from Spirulina supplements. Similarly, the majority of subjects demonstrated increased IDO activity and white blood cell count at 6 and 12 weeks of Spirulina supplementation. Spirulina may amend anemia and immunosenescence in older subjects. This study encourages extensive human studies to determine whether this safe supplement could prove beneficial in randomized clinical trials.
To govern the IDO enzyme activity, serum concentrations of tryptophan (mmol/l) and kynurenine (mmol/l) were measured by reverse-phase high-performance liquid chromatography, centered on the principle that tryptophan is converted to kynurenine by the action of IDO. As a result, the tryptophan/kynurenine ratio will precisely reflect the IDO activity. The IDO activity is calculated by determining kynurenine/tryptophan (mmol/mmol) ratio. Blood samples collected from subjects are tested for CBCs by means of routine laboratory methods and gathered data comprising hemoglobin (HGB), hematocrit (HCT), mean corpuscular HGB concentration (MCHC), mean corpuscular HGB (MCH), mean corpuscular volume (MCV) and white blood cells (WBCs).
Inhibitory effects of Spirulina on atherosclerosis are testified possibly via the inhibition of leptin secretion and improvement of leptin resistance. Earlier studies sustenance the benefits of Spirulina against fatty liver, oxidative stress, hyperglycemia, hypercholesterolemia, and arterial hypertension. From this study, it is postulated that Spirulina may provide a unique source of nutraceuticals that will enrich the homeostatic hematologic and immunological systems.16
According to some reports, it is proposed that Spirulina (Arthrospira) might have a beneficial effect in the prevention of cardiovascular diseases. In addition, studies have been conducted which show the effect of Spirulina intake on plasma lipids and blood pressure in humans. The results of the former studies suggest that Spirulina induces a tone-related increase in the synthesis/release of nitric oxide by the endothelium as well as an increase in the synthesis/release of a vasodilating cyclooxygenase-dependent metabolite of arachidonic acid and/or a decrease in the synthesis/ release of a vasoconstricting eicosanoid by the endothelium. In humans, Spirulina maxima intake lowers blood pressure and plasma lipid concentrations, especially triacylglycerols and low-density lipoprotein-cholesterol, and indirectly alters the total cholesterol and high-density-lipoprotein-cholesterol values.17
Spirulina is remarkably rich in phycocyanobilin (PCB), which recently is shown to act as a potent inhibitor of NADPH oxidase. This effect likely streamlines the broad range of anti-inflammatory, cytoprotective, and anti-atherosclerotic effects, which orally administered Spirulina, has achieved in rodent studies. In light of the central pathogenic role, which NADPH oxidase-derived oxidant stress plays in a vast range of disorders, spirulina or PCB-enriched spirulina extracts may have a notable potential for preserving and restoring health. Combined administration of flavanol-rich cocoa powder and Spirulina may have particular merit, in as much as cocoa can mask the somewhat disagreeable flavor and odor of spirulina, although the antioxidant impact of Spirulina can be expected to augment the bioactivity of the nitric oxide evoked by cocoa flavanols in inflamed endothelium. In addition, there is a reason to suspect that, by boosting cerebrovascular perfusion while quelling cerebral oxidant stress, cocoa powder and spirulina could work together in the prevention of senile dementia. Thus, food products featuring ample amounts of both high-flavanol cocoa powder and Spirulina may have substantial perspective for health promotion, and merit evaluation in rodent studies and clinical trials.18
C-Phycocyanin (C-PC), the major light harvesting biliprotein from Spirulina platensis is of superior importance because of its several biological and pharmacological properties. It is a water soluble, non-toxic fluorescent protein pigment with strong anti-oxidant, anti-inflammatory and anti-cancer properties. The biological and pharmacological properties of Spirulina were ascribed mainly to calcium-spirulan and C-Phycocyanin (C-PC).19
The antioxidant effect of Spirulina maxima is seen in several experimental models of oxidative stress. An experimental study was carried out to evaluate the antioxidant activity of Spirulina maxima against lead acetate-induced hyperlipidemia and oxidative damage in the liver and kidney of male rats. Control animals fed on a standard diet and did not collect lead acetate (Control group). Experimental animals were fed on a standard laboratory diet with or devoid of Spirulina maxima 5% in the standard laboratory diet and were treated with three doses of lead acetate (25 mg each/weekly, intraperitoneal injection) (lead acetate with Spirulina, and lead acetate without Spirulina groups). The results showed that Spirulina maxima inhibited the lead acetate from affecting the liver lipid levels and on the antioxidant status of the liver and kidney. Conversely, Spirulina maxima succeeded to improve the biochemical parameters of the liver and kidney towards the normal values of the Control group. Hence, it can be concluded that Spirulina maxima have protective effects on lead acetate-induced damage and the effects linked with the antioxidant effect of Spirulina.20
Non-alcoholic fatty liver diseases range from simple steatosis to non-alcoholic steatohepatitis. Spirulina maxima experimentally proved to retain in vivo and in-vitro hepatoprotective properties by maintaining the liver lipid profile. A study reported the hepatoprotective effects of orally supplied Spirulina maxima. Three Hispanic Mexican patients (a 43-year-old man, a 77-year-old man and a 44-year-old woman) undertook ultrasonography and were treated with 4.5 g/day of Spirulina maxima for three months. Their blood samples prior and after the treatment were determined for a presence of triacylglycerols, total cholesterol, high-density lipoprotein cholesterol, and alanine aminotransferase and low-density lipoprotein cholesterol levels. The results were assessed using ultrasound. Treatment had therapeutic effects as supported by ultrasonography and the aminotransferase data. Hypolipidemic effects were revealed too. This report establishes that Spirulina maxima can be considered as an alternative treatment for patients with non-alcoholic fatty liver diseases and dyslipidemic disorder.21
Spirulina has bioremediation potential as it can remove various pollutants such as metals, etc. A study was carried out to examine the possibility of using live Spirulina, in biologically eliminating aqueous lead of low concentration (below 50 mg/L) from wastewater. The Spirulina cells were first immersed for seven days in five wastewater samples having lead of different concentrations, and the growth rate was determined by light at a wavelength of 560 nm. The 72 h-EC50 (72 h medium effective concentration) was estimated to be 11.46 mg/L (lead). Subsequently, the lead adsorption by live Spirulina cells was accompanied. It was observed that at the initial stage (0–12 min) the adsorption rate was so rapid that 74% of the metal was biologically adsorbed. The maximum biosorption capacity of live Spirulina was assessed to be 0.62 mg lead per 105 alga cells. This study resulted in the inference that Spirulina’s rapid lead adsorption rate and high lead adsorption capacity made them well apposite for the removal of lead in wastewater. Moreover, living cells of Spirulina were found to have a high tolerance to lead and can be considered as an attractive adsorbate option for the biosorption of heavy metal contaminant. Yet, there are still many uncertainties linked with the development of treating wastewater by living algae, and more future work is required.22
Chlorella:
Chlorella comes from the Greek word ‘chloros’ (Χλωρός), which means green and the Latin suffix ‘ella’ referring to its microscopic size. It is a unicellular microalga that grows in freshwater and has been present on earth since the pre-Cambrian period 2.5 billion years ago, and since then its genetic integrity has remained constant.3 It is a spherical microscopic cell with 2–10 μm diameter. Most abundant pigment in C. vulgaris is chlorophyll, (1–2% dry weight) and situated in the thylakoids. Also, it contains carotenoids that act as accessory pigments by catching light. Βeta-carotene is often associated with the lipid droplets in the chloroplast. Primary carotenoids are associated with chlorophyll in thylakoids where they trap light energy and transfer it into the photosystem. These pigments have multiple therapeutic properties, such as antioxidant activities, protective effect against retina degeneration, regulating blood cholesterol, prevention from chronic diseases (cardiovascular and colon cancer) and fortifying the immune system.3 It shows many similarities with the plant cell. C. vulgaris has a single chloroplast with a double enveloping membrane composed of phospholipids. The outer membrane is permeable to metabolites and ions, but the inner membrane has a more specific function on proteins transport.3 The inner membrane of the mitochondrion is composed of thrice more proteins than phospholipids and it surrounds the internal space called the matrix, which contains the majority of mitochondrial proteins. It is an autospore and reproduces asexually and rapidly. The growth takes place in 3 forms: autotrophic, heterotrophic, mixotrophic and other methods of growth. Open ponds are the most common and cheapest way of an autotrophic production method for large-scale biomass production. Nevertheless, it has a major drawback, as it requires a strict environmental control to avoid the risk of pollution, water evaporation, contaminants, invading bacteria and the risk of growth of other algae species. In addition, some natural factors like temperature differences due to seasonal change are hysterical, and CO2 concentration and excess exposure to sunlight is difficult to manage. To overcome the shortcomings closed photobioreactor for growth in a managed environment is used. Heterotrophic growth does not require light and the biomass fed with organic carbon source is used. For Chlorella vulgaris, glucose, acetate, glycerol and glutamate with maximum specific growth rate obtained with glucose used as a carbon source. Due to C. vulgaris’ capability of combining both autotrophic and heterotrophic techniques by performing photosynthesis as well as ingesting organic materials such as glucose, mixotrophic method is the most appropriate method for C. vulgaris, as the cells are not strictly dependent on light or an organic substrate to grow.
The amino acid composition of C. vulgaris compares favorably with the standard profile for human nutrition proposed by World Health Organization (WHO), Food, and Agricultural Organization (FAO) because the cells of C. vulgaris synthesize essential and non-essential amino acids.3 During optimal growth conditions, C. vulgaris can reach 5–40% lipids per dry weight of biomass and is mainly composed of glycolipids, waxes, hydrocarbons, phospholipids, and small amounts of free fatty acids. The most abundant polysaccharide in C. vulgaris is starch, located in the chloroplast and is composed of amylose and amylopectin, and together with sugars, it serves as energy storage for the cells. Cellulose is a structural polysaccharide with high resistance, which is located on the cell wall of C. vulgaris as a protective fibrous barrier. Besides, one of the most important polysaccharides present in C. vulgaris is the β1-3 glucan, which has various health and nutritional benefits.3
Chlorophyll is most abundant pigment in C. vulgaris, which can reach 1–2% dry weight and is present in the thylakoids. Important amounts of carotenoids that act as accessory pigments by catching light are present. Beta-carotene is associated with the lipid droplets in the chloroplast, and primary carotenoids are associated with chlorophyll in thylakoids where they trap light energy and transfer it into the photosystem. These pigments have multiple therapeutic properties, such as antioxidant activities, protective effect against retina degeneration, regulation of blood cholesterol, prevention of chronic diseases (cardiovascular and colon cancer) and fortifying the immune system. These pigments are lipophilic, and their extraction is generally associated with lipid extraction.3 C. vulgaris has an important vitamin composition that are critical elements for cell growth and differentiation in the human body (Vitamin A) and has an antioxidant activity that acts as radical scavenger along with improving blood circulation and controlling muscle functions (Vitamins E and C).
Proteins from Chlorella vulgaris show excellent emulsifying properties, with any of the extraction methods. Solubilization of these proteins requires cell disruption via mechanical treatment. For high yield recovery (76%), alkaline treatment followed by isoelectric precipitation is an efficient process. For enhanced emulsifying properties, neutral conditions and tangential ultrafiltration used.23
Yeast and Fungi:
Candida sp. uses n-alkenes as the substrate and yields 65% crude protein. Candida utilis (Torula) uses ethanol, sulfite waste liquor as the substrate to yield 50-55% crude protein. Saccharomyces cerevisiae uses molasses to yield 53% crude protein. Among fungi, Fusarium graminearum uses glucose: Cephalosporiumeichhorniae uses cassava starch to yield 48-50% crude protein ; Chaetomium cellulolyticum uses agriculture and forestry wastes to yield 45% crude protein, and Paecilomyces varioti uses sulfite waste liquor to yield the highest amount of crude protein among fungi (55%) [24]. Dried yeast is used extensively as source of B-vitamin in nonconventional food products.25 Yeast growing on hydrocarbons has a high yield. The heat produced by growth on hydrocarbons is greater per unit of cells produced than when carbohydrate is used. The temperature of growth for most yeasts or molds proposed for use as sources of SCP is in the range of 25-40 degree Celsius.25 Yeast, under the most favorable condition, has a generation time of about 1-3 hours, while filamentous fungi can double their masses in 4-12 hours. The lower pH and the rapid buildup of the cell population reduce the risk of bacterial toxins in yeast production.26 Filamentous fungi have slow growth rate than yeast.24
Yeast is one of the richest sources of vitamin B: thus it has a role in animal nutrition as a feed supplement (0.5-1.5%). The concentrations of B vitamins in fungal mycelium are usually lower than yeast.26 Protein from yeast and fungi has up to about 50 – 55 % protein content and it has high protein –carbohydrate ratio than forages. It is rich in lysine but deficient in methionine and cysteine. It has an excellent balance of amino acids and is rich in B –complex vitamins and more suitable as poultry feed .24 The cell wall of yeast maybe non-digestible or may possess unacceptable odor or colour :thus the cells should be killed before ingesting. High nucleic acid content is there in both yeast and fungi.
The amino acid compositions of both the intact cells of the yeast, Saccharomyces fragilis, grown batch wise and continuously on crude lactose, and of extracted protein were determined. The composition of whole cells of S. fragilis grown under changed conditions during batch and continuous cultivations was quite alike, and the content of lysine and leucine was very extraordinary. The concentrations of amino acids in yeast protein isolates varied with diverse preparation methods. Yeast protein extracted with water and heat precipitated at 80 degrees, pH 6.0, contained the supreme amount of essential amino acids. Methionine and tryptophan were apparently the most limiting amino acids in all protein isolates prepared from S. fragilis.27
Bacteria:
Among bacterial species, Cellulomas and Alcaligenes are the most habitually used bacterial species as a single cell proteins source. Impending phototrophic bacterial strains recommended for Single Cell Protein production are used. Some researchers also suggest the use of methanotrophic and other bacterial species for protein production. The generation time of Methylophilus Methylotrophus is about 2 hours and this bacterium in animal feed is used. In general, produce a more favorable protein composition than yeast or fungi. Consequently, the large quantities of Single Cell Protein animal feed using bacteria made. Characteristics that make bacteria apposite for this application include rapid growth of bacteria, short generation times of bacteria almost can double their cell mass in 20 minutes to 2 hours. They are also capable of growing on a variety of raw materials that range from carbohydrates such as starch and sugars to gaseous and liquid hydrocarbons, which include methane, and petroleum fractions, to petrochemicals such as methanol and ethanol, nitrogen sources that are useful for bacterial growth include ammonia, ammonium salts, urea, nitrates, and the organic nitrogen in wastes. In addition, it is suggested to add a mineral nutrient supplement to the bacterial culture medium to fulfill dearth of nutrients that may be absent in natural waters in concentrations adequate to support growth.12
For cultivation of protein, bacteria recovered by centrifugation are used. Bacteria produce proteins that contain more than 80% protein even though they have a small amount of sulfur containing amino acids and are high in nucleic acid content. It has a high possibility of contamination during the production process and cell recovery sources many complications. It may also contain endotoxins from gram-negative bacteria [12]. Bacteria can grow more rapidly and efficiently than yeast on economic substrates, and they provide a greater content of protein. Bacteria has 50-65% dry weight of protein,1.5-3.0% dry weight of fat, 3-7% dry weight of ash and 8-12% dry weight of nucleic acid.24
Aeromonas hydrophylla uses lactose, Acromobacter delvacvate uses n-alkanes, Acinetobacter calcoacenticus uses ethanol, and Bacillus megaterium uses non-protein nitrogenous compounds. Bacillus subtilis, cellulomonas sp., flavobacterium sp., Thermomonospora fusca use cellulose and hemicellulose. Lactobacillus sp. uses glucose, amylose and maltose and Methylomonas methylotrophus, M.clara use methanol and Pseudomonas fluorescens uses uric acid and other non-protein nitrogenous compounds.5 It is capable of growing on a variety of raw materials, extending from carbohydrates such as starch and sugars, to gaseous and liquid hydrocarbons such as methane and petroleum fractions, to petrochemicals such as methanol and ethanol. Apposite nitrogen sources for bacterial growth comprise of ammonia, ammonium salts, urea, nitrates, and the organic nitrogen in wastes. To the bacterial culture medium to endow nutrients, a mineral nutrient supplement that may not be present in natural waters in concentrations sufficient to support growth added.6
Budding phototrophic bacterial strains for single cell protein production suggested. Some researchers advise the use of Methanotrophic and other bacterial species for single cell protein production.6 Liquid culture is ideal for growing unicellular organisms, which are bacteria. When examining analytical data on amino acid composition, there is the possibility that certain of the amino acids may be present as the D-isomer. In case of bacteria, D-alanine and D-glutamic acid are frequently present in the cell walls of bacteria.25 Single cell protein from different photosynthetic bacteria, grown on clarified supernatant, is rich in essential and sulfur amino acids. Rhodopseudomonas capsulate is the best-suited microorganism for cell protein.28 Photosynthetic bacteria is rich in B group of vitamins has been testified. Use of photosynthetic bacteria is of substantial importance in pisiculture, the poultry and horticulture.28
CONCLUSION:
Single cell protein from Spirulina and non-Spirulina sources can prove to be of great importance in future. Due to their exceptional properties, they can be a source of food for the malnourished people. It has a potential to be an excellent source of protein. Besides protein, it has various other vitamins and minerals required to carry out various biochemical reactions in our body. Both the sources have pros and cons and thus possess great potential to be a cloned product.
CONFLICT OF INTEREST:
No conflict of interest
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Received on 31.07.2018 Modified on 21.09.2018
Accepted on 29.10.2018 © RJPT All right reserved
Research J. Pharm. and Tech. 2019; 12(10):5051-5058.
DOI: 10.5958/0974-360X.2019.00877.1