What is Chlorella

The unicellular, mostly fresh-water chlorococcal algae of the genus Chlorella belong to the most important among the many algal species known - important in terms of their biological value, growth rate and suitability for controlled cultivation. Their predominantly spherical cells, 5-10 micrometres in diameter (if placed in a line, 100-200 of these cells would take up no more than a millimetre), have a simple life cycle. The youngest (daughter) cell grows to attain the stage of an adult (mother) cell, which then divides to usually 4-8 new daughter cells. The growth cycle is then repeated. Under suitable conditions (with a sufficient supply of nutrients, light, and a suitable temperature), the growth rate is very fast, a doubling of their biomass taking place in 3-6 hours (cultivated higher plants would need at least 10 days to do that). Microscopic pictures of one of the Třeboň production Chlorella cultures can be seen in Figs. 1 and 2.
The cell content of Chlorella is extraordinarily valuable (see Tables 1-4). Some 60 % of the cell is formed from proteins, which in their composition resemble animal rather than plant proteins. These proteins contain all the essential amino acids in well-balanced proportions, i.e. proteins that cannot be synthesised by the human or animal body. (For comparison - soybeans, the highest valued plant source of proteins, do not contain more than 35 % proteins). Saccharides, in particular starch, form about 10 % of the cell content's dry weight, while lipids make up around 15 %. These are formed for the most part by essential unsaturated fatty acids. These acids are indispensable for the human body as starting materials for the production of a number of complex compounds (prostacyclins, prostaglandins, leukotrienes) that regulate the body level of cholesterol, control blood pressure and prevent blood clotting, and therefore play an important part in the prevention of cardiovascular disorders (2-8). About 8 % öf Chlorella's dry weight is made up of fibre and cell-wall polysaccharides, which are assumed to induce the production of the antiviral agent interferon (9).

Table 1 - Basic chemical biomass composition of a production strain of Chlorella kessleri (% algal dry weight)

* The proportion of essential unsaturated fatty acids (oleic, linoleic, linolenic) in the total fatty acids, under optimum growth conditions, is in the range of 40-60 %.

Table 2 - The percentage of essential amino acids in Chlorella and other protein-rich sources

In addition to 3-4 % chlorophyll (about 10 times more than in lucerne, the most common source of chlorophyll), a green pigment with a high content of magnesium, Chlorella contains also carotenoids, orange and yellow pigments. The most valuable of these is beta-carotene, a compound that the human body cannot synthesize. The pigmentation efficiency of algal carotenoids is unequalled among plants: enrichment of a feed mixture for egg-laying hens with 2 % Chlorella rises the concentration of carotenoids in the yolk 5 times (10). Apart from being well-known as provitamin A, beta-carotene has lately been found to exert an important protective action in the prevention of tumour malignancies. Significant, also, are its very strong antioxidative effects - protecting body cells and tissues against the adverse effects of free radicals, which disrupt the homeostasis of cell structures and lower the resistance of an organism to diseases (11, 12).
A number of experiments have shown that the biological efficiency of natural beta-carotene is higher than that of the synthetic one, commonly used as a colouring agent in the food industry. The massive use of synthetic beta-carotene has given rise to the suspicion that, with prolonged use, it may cause tumour growth (13). The amount of beta-carotene in Chlorella is in the range of 0.10 to 0.40 % dry weight, i.e. about 10-20 times more than in carrots, the best-known plant source of this substance.
An important component of Chlorella cells is biologically complexed, and therefore readily-utilised, essential minerals (phosphorus, potassium, magnesium, calcium and especially iron). Their concentration in the algae is usually higher than that in land plants (Table 3). For instance, the level of iron in Chlorella is 30 times higher than that in spinach or chives, i.e. plants that are among the richest in iron. Important is the content of trace elements - elements forming part of enzyme complexes and vitamins necessary for normal metabolism in both the developing and adult body. These elements include in particular manganese, zinc, molybdenum, copper and cobalt. Increased attention has recently been paid to the study of the cellular functions of selenium and chromium. Although the need for these elements is very low, many populations of industrial countries are exhibiting their deficit. The selenium intake per person in the Czech Republic is strongly subnormal for more than 60 % of the population tested (14,15).
Selenium is the functional component of glutathione peroxidase which, in conjunction with vitamin E, buffers the destructive effect of peroxidation reactions on living cells. The protective function of selenium involves also its role in the synthesis of the thyroid hormones (16,17). Furthermore, it reduces the toxicity of heavy metals in the organism because it aids in their binding in the form of harmless complexes (18). All these functions regulate virtually the whole metabolism.
An equally-important element is chromium, which stabilises the tertiary structure of proteins and forms part of the glucose tolerance factor (GTF) that enhances the effect of insulin, with the subsequent improved control of blood sugar levels.
These trace elements in the algal cells are most often chelated with amino acids. Their concentration and type of binding can be considerably modified. This offers us the possibility of obtaining algal biomass with a defined, mostly-increased content of desirable elements - or their mixture in a natural organic form. An organic form enhances the biological efficiency of these elements. The utilisation of the elements is thus promoted - thereby attaining much higher levels than that achieved in the many recommended artificial mineral mixtures which contain the desirable elements in the form of inorganic compounds (19).
Another group of substances which is present in Chlorella at higher levels than in other plants is vitamins. Table 4 shows a comparison of their levels in Chlorella and in some common vitamin-rich sources. Noteworthy is the high content of group-B vitamins, ascorbic acid (vitamin C), nicotinic acid (vitamin B3) and tocopherols (vitamin E).

Table 3 - Proportion of mineral substances and important trace elements in Chlorella dry weight (mg /100 g)

Table 4 - Comparison of vitamin content of Chlorella with that of other vitamin-rich sources

The last, but certainly not least, of the biologically-active substances that has made Chlorella famous is the so-called Chlorella Growth Factor (CGF), a water-extractable cell fraction containing free amino acids, peptides, glycoproteins, polyamines, some vitamins, minerals and other, as yet not-exactly-defined components. The effects of the extract are striking:
It promotes tissue regeneration, cell growth and division (20-26). It stimulates the production of leukocytes and their phagocytic activity, i.e. the ability to eliminate foreign bacteria (27,28) and also the production of lymphocytes responsible for the synthesis of antibodies - important factors in the immunity against infections (29,30,31). It is a suitable dietary supplement during the administration of probiotics, i.e. substances positively affecting the composition of intestinal microflora (32). It has been shown that, following an administration of the algal extract, an organism exhibits better regeneration of damaged tissue caused by ionising radiation (33-38). Chlorella extracts have found their use in topical applications, e.g. in the treatment of chronic inflammations, eczemas, crural ulcers, burns and other badly-healing wounds, which are healed to a fully-functional tissue (39-42). Japanese laboratories have repeatedly published data on the anti-tumour activity of the algal extract (43-53).
The nutrient solution in which Chlorella has been cultured also displays a conspicuous stimulatory effect when used for watering freshly-planted fruit or forest trees, or vegetables. This has been attributed to its stimulatory effects on a plant's root-taking and growth (54). The stimulatory effect is ascribed, apart from other components, to compounds of the phytohormone group, which have been identified in the algal extracts (55,56,57).

The Chlorella from Třeboň in everyday use

The first establishments making use of the algae from Třeboň - and making products from the algae - have been Imuna Šarišské Michal´any and Bioveta, Ivanovice in Haná. The pharmaceutical company Imuna have used a Chlorella preparation to enrich some of their media for microbial culture. The growth of the microorganisms was then made substantially faster (69). Bioveta used an algal extract obtained from a production strain of heterotrophically-cultivated Chlorella (i.e. the source of energy and carbon for the building of the algal cell body is not sunlight and CO2 but glucose) to produce Ivastimul, a veterinary-supportive therapeutic drug (70,71). Extensive experiments performed for several years, both here and abroad, showed that the preparation enhances the immunity against infections and improves the health condition of animals (72,73).
One of the largest corporations interested in Chlorella is currently the dynamic Brno enterprise Algafeed. Based on prescriptions and formulations developed at the Institute of Physiology, Veterinary and Pharmaceutical Faculty, Brno University, and verified in tests conducted in collaboration with a number of other research institutions, Algafeed supplements animal feeds with Chlorella. The algal supplement enhances the immunity to infections in the animals, and improves their reproduction, promotes weight gain, quality of fur, meat and also yolks in laying hens (74-80). New attractive products that are to be gradually introduced into human nutrition and into fodder production also include Chlorella with a programmed high-content of biologically-bound, physiologically-important trace elements.
A high-quality product in the field of human dietary supplements is the patented Algamin (81) - which is, in fact, the popular product of the Braník Brewery, Pangamin (dried brewers´ yeast) enriched with Chlorella in an amount that ensures an optimum supplementation of the active Pangamin components with active algal constituents. Another product is Unilakt of the Prague producer HM-Harmonie, which contains, apart from Chlorella, fibre and pure cultures of bifidobacteria which adjust the intestinal flora composition. Pure Chlorella, powdered or in tablets, can be obtained from Algafeed under the trade name Viradalgin. The first Czech cosmetics products enriched with extracts from Třeboň algae, are a soothing ointment and a set of skin and regeneration creams of the Třeboň company Dihe. Some of these products are shown in Fig. 7.
Other products based on Chlorella are in the phase of development and long-term tests.
What about Chlorella as a foodstuff? Can we envisage it as a daily component of our diet? Yes, we can - that would be the automatic answer of astronauts who took Chlorella from Třeboň on their space sojourns. Its taste is a bit exotic (it resembles spinach with a fish flavour) but is delicious as a supplement of salads, sauces, dressings, cheese spreads, soups, etc. In the sixties, the Jordán hotel in Tábor offered algae in more than forty variations. At that time, these dishes did not yet have the (quite necessary today) approval of the Ministry of Public Health for the use of algae in human nutrition, and the quality of the algae was not controlled as strictly as it would be today, but despite this (or because of it?), these dishes tasted exquisitely. We are going to revive this tradition, this time directly in Třeboň.