An Elusive Green Dream?

You don’t need to know a lot about cows to realise that their genetic code is different to that of horses.

Scientists became interested in algae as a possible food source in the 1960s. You could feed the whole world in this way, idealists thought, and they set to work. Hardly surprising, since algae are tiny plants that can grow quickly using few S resources. They contain important nutrients to boot. For instance, algae contain up to 70 per cent protein. They make healthy ingredients such as vitamins, minerals, antioxidants and unsaturated fatty acids atlittle cost. The fact that algae might be able to clean exhaust gases andwaste water – after all, they use ‘water pollutants’ and carbon dioxidefor their metabolism – and turn them into valuable raw materialsseemed promising. Micro-algae are unicellular plants. They grow injust 12 to 24 hours and are not particularly demanding. They need only need light, carbon dioxide, water, and a minimal quantity of nutrients such as phosphates, nitrates and sulphates.

The first open-air culture ponds were in Mexico, the United States (including Hawaii) and Australia. Many still exist. They are large shallow lakes, about 30cm deep, covering several hectares. They are not very efficient: the yield is only 0.5g to 1g of algae per litre of water. That’s due to poor penetration of light, sedimentation of algae and barely controllable climatic conditions.

The method is indiscriminate and only suitable for some algae: strains that can be cultivated selectively or thrive under competition from other algae and bacteria. But, because of the large volumes and the low ‘reactor’ costs, these flooded .elds are still the major source for commercial micro-algae and micro-algal products.

The ideal of ‘feeding the world’ was abandoned long ago. But the health-promoting substances present in algae make the organism highly interesting for commercial cultivation. And the market for algae and algal ingredients is growing steadily. Most of the algal biomass used as food supplements in western countries or as ingredients for cosmetics. Algae produce some substances that are difficult to make by chemical means and therefore expensive, such as the red pigment astaxanthin, a carotenoid. In the US, this is produced on a large scale by the algae, Haemotococcus pluvialis. Astaxanthin is also a strong antioxidant and is therefore believed to contribute to the prevention of cardiovascular diseases, skin diseases and age-related eye defects. Such valuable ingredients supplied by algae are the subject of intensive research. Essential fatty acids are another example. Some algae are rich in omega-3 fatty acids and long-chain poly-unsaturated fatty acids (PUFAs), such as EPA (eicosapentaenoic acid). Types of algae Microalgae are microscopic – unicellular – plants. The autotrophic strains from this heterogeneous group of organisms use light as a source of energy to convert carbon dioxide and water into biomass. They use chlorophyll for this assimilation. Mixotrophic strains can use both light and organic substances such as glucose as their energy source for growth. Heterotrophic strains do not need light to reproduce, but derive all their energy from the organic substances. Macroalgae are multi-cellular, such as the group of seaweeds. Why algae?

High concentrations of healthy ingredients for food and feed

High concentrations of natural colorants

Contain up to 70 per cent protein

Alternative for green herbs

Whole organism can be used as a food supplement (contains minerals, trace elements, metals)

Production of expensive fine chemicals for cosmetics

Consume exhaust gases

Convert contaminated waste water and liquid waste into rich biomass

Potential source of energy by production of hydrogen

Fish feed for the booming aquaculture business

Potential source of ingredients for medicines

Algae versus fish Ingredient suppliers also have discovered algae as a useful source. For example, Nutrinova produces a highly concentrated, vegetarian form of DHA (docosahexaenoic acid). The company markets this omega-3 fatty acid under the Nutrinova DHA brand name. While DHA-oils are commonly extracted from fatty cold water fish, DHA is extracted from microalgae via a patented fermentation process. Nutrinova’s DHA is said to have many advantages over typical fish oil. It contains a much higher concentration of DHA and a lower amount of undesirable fatty acids. Infants and embryos need these ingredients to build the brain and the retina. But they’re also interesting to adults, because of they are believed to help prevent cancer and cardiovascular diseases. Whole algae Spirulina and Chlorella are commercially available as powder or pills in organic food shops. Antioxidants, omega-3 fatty acids and vitamins (B and E) are produced as functional ingredients. The algae Dunaliella salina is also a recognised source of natural colorants (betacarotene). At the moment, most of the market still consists of whole algae, produced in culture ponds outside Europe. For food supplements it is necessary to isolate the components from the organisms, extract them and process them into pure substances. This is only possible using more advanced technologies, such as membrane .ltration, centrifuging, fiocculation or (chemical) extraction. That is why the cultivation methods should be advanced. Economic production needs high yields. Open lakes have limitations for growing algae. So with rising demand, the focus shifted to .nding alternatives. A technologically more advanced method of making algae grow more ef.ciently was developed: the photobioreactor. This reactor is a translucent, closed vessel in which the temperature and composition of the substrate—the medium in which the algae grow—are controlled, and the intensity of the incoming light is regulated accurately. The first laboratory-scale photobioreactors were glass cylinders with water in which air enriched with carbon dioxide is injected from the bottom. Artificial light (from .uorescent or discharge lamps) produces the energy required for the photosynthesis so that the necessary organic substances can be produced.