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Chlorella is a genus of single-celled green algae, belonging to the phylum Chlorophyta. It is spherical in shape, about 2 to 10 μm in diameter, and is without flagella. Chlorella contains the green photosynthetic pigments chlorophyll-a and -b in its chloroplast. Through photosynthesis it multiplies rapidly requiring only carbon dioxide, water, sunlight, and a small amount of minerals to reproduce .

The name Chlorella is taken from the Greek word chloros meaning green and the Latin diminutive suffix ella meaning "small". Germanmarker biochemist and cell physiologist Otto Heinrich Warburg, awarded with the Nobel Prize in Physiology or Medicine for his research on cell respiration in 1931, also studied photosynthesis in Chlorella. In 1961 Melvin Calvin of the University of California received the Nobel Prize in Chemistry for his research on the pathways of carbon dioxide assimilation in plants using Chlorella. In recent years, researchers have made less use of Chlorella as an experimental organism because it lacks a sexual cycle and, therefore, the research advantages of genetics are unavailable .

Many people believed Chlorella could serve as a potential source of food and energy because its photosynthetic efficiency can, in theory, reach 8%, comparable with other highly efficient crops such as sugar cane. It is also an attractive food source because it is high in protein and other essential nutrients; when dried, it is about 45% protein, 20% fat, 20% carbohydrate, 5% fiber, and 10% minerals and vitamins. However, because it is a single-celled algae, harvest posed practical difficulties for its large-scale use as a food source. Mass-production methods are now being used to cultivate it in large artificial circular ponds.

Aquarium

Chlorella can create green and opaque water problems in aquaria. Chlorella can grow due to high nitrate and phosphate levels or direct sunlight. Decreasing phosphate and nitrate by partial water change and moving the aquarium to shade can help alleviate the problem.

Chlorella as a food source

Following global fears of an uncontrollable population boom, during the late 1940s and the early 1950s Chlorella was seen as a new and promising primary food source and as a possible solution to the then current world hunger crisis. Many people during this era thought that world hunger was a growing problem and saw Chlorella as a way to end this crisis by being able to provide large amounts of high quality food for a relatively low cost.

Many institutions began to research the algae, including the Carnegie Institution, the Rockefeller Foundation, the NIHmarker, UC Berkeleymarker, the Atomic Energy Commission, and Stanford Universitymarker. Following WWII, many Europeans were starving and many Malthusians attributed this not only to the war but to the inability of the world to produce enough food to support the currently-increasing population. According to a 1946 FAO report, the world would need to produce 25 to 35 percent more food in 1960 than in 1939 to keep up with the increasing population, while health improvements would require a 90 to 100 percent increase. Because meat was costly and energy-intensive to produce, protein shortages were also an issue. Increasing cultivated area alone would go only so far in providing adequate nutrition to the population. The USDAmarker calculated to feed the U.S. population by 1975, it would have to add 200 million acres (800,000 km²) of land, but only 45 million were available. One way to combat national food shortages was to increase the land available for farmers, yet the American frontier and farm land had long since been extinguished in trade for expansion and urban life. Hopes rested solely on new agricultural techniques and technologies. Because of these circumstances, an alternative solution was needed.

To cope with the upcoming post-war population boom in the United States and elsewhere, researchers decided to tap into the unexploited sea resources. Initial testing by the Stanford Research Institute showed Chlorella (when growing in warm, sunny, shallow conditions) could convert 20 percent of solar energy into a plant which when dried, contained 50 percent protein. In addition, Chlorella contained amino acids, fat, calories, and vitamins. The plant's photosynthetic efficiency allowed it to yield more protein per unit area than any other plant—one scientist predicted 10,000 tons of protein a year could be produced with just 20 workers staffing a one thousand-acre (4 km²) Chlorella farm. The pilot research performed at Stanford and elsewhere led to immense press from journalists and newspapers, yet its promise was never realized. Chlorella was a seemingly-viable option because of the technological advances in agriculture at the time and the widespread acclaim it got from experts and scientists who studied it. Algae researchers had even hoped to add a neutralized Chlorella powder to conventional food products, as a way to fortify them with vitamins and minerals. However, the hype far surpassed the productivity of the plant, and early estimates of its success were proven to be no more than exaggerated optimism.

In the end, scientists discovered Chlorella would be much more difficult to produce than previously thought. The experimental research was carried out in laboratories, not in the field. In order to be practical, the entire batch of algae grown would have to be placed either in artificial light or in shade to produce at its maximum photosynthetic efficiency. Also, for the Chlorella to be as productive as the world would require, it would have to be grown in carbonated water, which would have added millions to the production cost. A sophisticated process, and additional cost, was required to harvest the crop, and for Chlorella to be a viable food source, its cellulose cell walls would have to be pulverized. The plant could reach its nutritional potential only in highly-modified artificial situations. Economic problems and the public's distaste for the flavor of chlorella and its byproducts ultimately led to the plan's demise.

Since the growing world food problem of the 1940s was solved by better crop efficiency and not from a "super food", Chlorella has lost public and scientific interest for the time being. Chlorella can still be found today in rare occasions from companies still promoting its "super food" effects.

Nutrition

Chlorella has been found to have anti-tumor properties when fed to mice.Another study found enhanced vascular function in hypertensive rats given oral doses of chlorella.

Chlorella is a complete protein. It is also packed with calories, fat, and vitamins.At its onset, Chlorella was suggested as a "dirt-cheap to the human diet. However, later studies proved otherwise. Chlorella actually loses most of its nutritional value when altered or processed in any way. No longer considered an effective protein, pro-Chlorella supporters focused on other supposed health benefits of the algae, such as claims of weight control, cancer prevention, and immune system support.

Under certain growing conditions, Chlorella yields oils high in polyunsaturated fatsChlorella minutissima has yielded EPA at 39.9% of total lipids.

Evidence of health and healing effects

Like Aphanizomenon flos-aquae (blue green algae) clinical studies on chlorella suggest effects including dioxin detoxification in humans and animals, healing from radiation exposure in animals and the ability to reduce high blood pressure, lower serum cholesterol levels, accelerate wound healing, and enhance immune functions in humans. However, the use of Chlorella for healing effects has received criticism.

Early reception and scientific backing

When the preliminary laboratory results were published the reaction of scientific literature backed the possibilities of the supposed superfood. Science News Letter praised the optimistic results in an article entitled "Algae to Feed the Starving." John Burlew, the reported editor of Carnegie Institute stated, "the algae culture may fill a very real need," which Science News Letter turned into "future populations of the world will be kept from starving by the production of improved or educated algae related to the green scum on ponds." The cover of the magazine also featured Arthur D. Little's Cambridge laboratory, which was a supposed future food factory. A few years later, the magazine published an article entitled "Tomorrow's Dinner", which stated, "There is no doubt in the mind of scientists that the farms of the future will actually be factories." Science Digest also reported, "common pond scum would soon become the world's most important agricultural crop." Yet the optimistic initial promises of the algae fell short when further testing was conducted.

Current challenges in mass production

Although the production of Chlorella looked promising and involved creative technology, it would not prove to be economically viable in the market. In competition with Spirulina, soybean products and whole-grains, algae were less successful in the health-food market. In practice, algae was not as cheaply or easily harvested as technicians predicted it would be 40 years earlier. The efficiency of other "normal" dietary products actually turned out to supersede that of algae growth and production. Aside from production inefficiencies, Chlorella, as it turned out, did not capture the benefits of photosynthesis and sunlight as predicted. After a decade of experimentation, studies showed that following exposure to sunlight, Chlorella captured just 2.5 percent — not much better than conventional crops. Chlorella, too, was found by scientists in the 1960s to be impossible for humans and animals to digest in its natural state due to the tough cell walls encapsulating the nutrients, which presented further problems for the use of algae in American food production. Since then, multiple methods have been developed to crack/break down this cell wall to make the nutrients available for digestion.

See also



References

  1. I. Zelitch, Photosynthesis, Photorespiration and Plant Productivity, Academic Press, 1971, p.275.
  2. .
  3. Immunopharmacol Immunotoxicol - Oral administration of Chlorella vulgaris augments concomitant antitumor immunity
  4. Ethnopharmacol - Immunomodulation by a unicellular green algae (Chlorella pyrenoidosa) in tumor-bearing mice
  5. Cancer Immunol Immunother - Antitumor effect induced by a hot water extract of Chlorella vulgaris (CE): resistance to Meth-A tumor growth mediated by CE-induced polymorphonuclear leukocytes
  6. J Nutr Sci Vitaminol (Tokyo) - Effect of chlorella and its fractions on blood pressure, cerebral stroke lesions, and life-span in stroke-prone spontaneously hypertensive rats
  7. Nakano, S et al. “Maternal-fetal distribution and transfer of dioxins in pregnant women in Japan, and attempts to reduce maternal transfer with Chlorella (Chlorella pyrenoidosa) supplements...” Chemosphere 2005 Dec; 61(9): 1244–55.
  8. Takekoshi, H et al. “Effect of Chlorella pyrenoidosa on fecal excretion and liver accumulation of polychlorinated dibenzo-p-dioxin in mice”. Chemosphere 2005 Apr; 59(2): 297b–304.
  9. Singh, SP et al. “Post-exposure radioprotection by Chlorella vulgaris (E-25) in mice”. Indian J Exp Biol. 1995 Aug; 33(8): 612–5.
  10. Merchant RE and Andre, CA. “A review of recent clinical trials of the nutritional supplement Chlorella pyrenoidosa in the treatment of fibromyalgia, hypertension, and ulcerative colitis”. Altern Ther Health Med. 2001 May–Jun; 7(3): 79–91. Review.
  11. E.W. Becker (1994). Microalgae: Biotechnology and Microbiotechnology. Cambridge University Press.


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