In order to survive from famine the Chinese used the microalgae Nostac more than two thousand years ago---probably the first human use of microalgae. In Chad and Mexico the Arthrospira species of microalgae was used in earlier times. Since then the use of microalgae has evolved gradually. Today they are used as human nutritional supplements, as animal feed additives, in acquaculture, and in cosmetics

An overview

Microalgae is important in terms of the biodiversity it depicts (more than 500,000 species exist) and also because it generates the maximum oxygen into the atmosphere and effectively removes carbon dioxide from the atmosphere as well. Microalgae are basically unicellular and can be seen only under the microscope unlike macro-algae that can be seen by the naked eye. Yet microalgae can be seen when they cluster up in chains or groups. But importantly, microalgae do not have distinct plant attributes like, roots, leaves and so on. Microalgae are a treasure house of important compounds like: antioxidants, fatty acids, peptides, toxins and enzymes. Research efforts directed at microalgae are mostly based on biotech initiatives.

Size

In size microalgae could range from one micron to a little above 2millimeters and can be seen in spectacular shapes and patterns under the microscope. Some microalgae grow tall while others grow flatly along the surface. They can be seen in different bright colors as well like red (Rhodophyta), green (Chlorophyta), brown (Phaeophyta) and blue.


Importance of microalgae

Microalgae can be seen in the seas, lakes and rivers etc. The reason why they are important is because of their prominent position in the aquatic food chain. They are the primary source of food for the zooplankton (includes small protozoans and large metazoans) that we see floating in water bodies like lakes and streams. The zooplanktons in turn are source of food for the larger aquatic animals. Therefore, without microalgae marine life would just not exist.

The second reason is the contribution of microalgae to the earth's supply of oxygen. A major portion of the earth's oxygen supply is made by the tiny cells of this organism---phytoplankton.


Composition of microalgae

The composition of microalgae is largely dependent on the species and the cultivation parameters referenced. However, the following constituents are generally seen.
• The cells of microalgae can synthesize amino acids
• Carbohydrates in the form of starch, sugars and glucose are present
• The Protein content is high
• The lipids in algae are in the form of saturated and unsaturated fatty acids.
• Plenty of chlorophyll and carotenoids
• All types of vitamins including folic acid, biotin and pantothenic acid (Vitamin B5)
• Ascorbic acid is also found in abundance in microalgae


On the negative side microalgae have nucleic acids, toxins and heavy-metal components which raise problems in commercial exploitation of microalgae.

In cosmetics

Microalgal extracts are used in following types of cosmetic preparations

• Anti-aging preparations
• Refreshing care products---emollients, anti-irritants
• Sun protection creams
• Hair- care products


In fact many leading cosmetic companies have their own captive micro-algal production systems. However, not all microalgae species are suitable for use in cosmetics. But some are.
These are:
• Arthrospira
• Chlorella


Examples of microalgae used in cosmetics

Pepha-Tight: A skin tightening product for combating wrinkled skin with ingredients from the algae Nannochloropsis oculata in combination with polysachharide fractions.

Pepha-Ctive: A product for stimulating skin cell proliferation using ingredients from the algae D. salina

Protulines: A vegetable protein extract from Spirulina platensis for tightening the skin and combating skin aging process especially in face and eye contour products and in anti-stretch mark products.

Dermochlorella: This product which is an extract from the green microalgae Chlorella vulgaris enhances skin collagen synthesis and helps reduce wrinkles. This product which is rich in natural aminoacids and oligopeptides exerts anti-angiogenic action on the skin and is useful to treat acne rosacea.

As you will note, the use of microalgae in cosmetics is mostly in face and skin care products.


In acquaculture

Microalgae have an important role in the food chain. They enrich zooplankton which is at the base of the food chain and which in turn is food for fish and larvae.

Microalgae are suitable for use as feed in aquaculture especially for larvae. In that case the content of polyunsaturated fatty acids in them (what are called PUFA) is important. These acids are:
eicosapentaenoic acid (EPA)
arachidonic acid
docosahexaenoic acid (DHA)

The maximum content of arachidonic acid and EPA's are to be found in the microalgae species Eustigmatophytes while the maximum content of DHA's is to be found in the microalgae species Prymnesiophytes

In general, the cell protein content serves as the basis for using microalgae as aquaculture feed.
The commonly used microalgae species in aquaculture are:

Category~diatoms

• Skeletonema costatum
• Thalassiosira pseudonana,
• C. calcitrans


Category ~ flagellates

• Isochrysis galbana
• Tetraselmis suecica


Category~ chlorococcalean

• Chlorella spp


In animal nutrition

Microalgae can be a useful feed component to ensure animal nutrition and in fact most of the commercially made algae are used for making animal feed especially using the species Arthrospira.

Chicken, Swine and Pets

One of the interesting findings is that, egg yolk of chicken fed with microalgae had reduced cholesterol levels and was darker in color indicating higher carotenoid content.

The microalgae Porphyridium sp used as feed supplement for chicken was found to be beneficial. Spirulina and Haematococcus pluvialis are some of the other microalgal species used as feed supplements for broiler chicken.

Docosahexaenoic acid- enriched microalgae of the species Schizochytrium sp is given as feed supplement for swine so as to help it gain in weight. Pet foods with microalgae extracts bettered the appearance of the pets in terms of shining hair coat etc. Spirulina extracts were found to enhance the functioning of the animal's immune system.

Constraints

One of the constraints in using microalgae as animal feed supplements is the extent of digestibility. The other is the fact that microalgae of marine origin have higher salt content. Another issue is the removal of nucleic acids and toxins from the microalgae.


Conclusion

A lot remains to be done as regards research on microalgae from a biotech point of view. For example, only a few hundred species of microalgae have been evaluated in terms of their content and utility value. Furthermore, only a few varieties have been cultivated for industrial use especially in photobioreactors as their growth in photobioreactors has been found to be rather on the slower side. On the contrary, the growth of microalgae in outdoor cultivation scenario has been abundant.

An area of possible research in the future could be how to genetically improve algal strains. The idea of transgenic microalgae is yet to materialize substantially and could be a matter of future research leading to perhaps several new drugs.

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