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Microalgae can produce more than just fuel

Microalgae have played an important role as animal feed or food supplements for decades. They can also produce complex chemical compounds. This so-called material use of microalgae is already a major economic sector. However, when it comes to algal biotechnology, they are almost universally seen as just energy sources.

The mass production of spirulina began in the 1960s. Back then, seaweed farmers produced around 50 tons of spirulina per year in large, open water pools. Times have changed: spirulina is no longer regarded as algae and production volumes have multiplied. Spirulina lacks what algae have, namely a nucleus. For this reason, spirulina is now regarded as cyanobacterium. However, the term “algae” stubbornly persists. Packages of spirulina products still promote the contents as algae. More than 12,000 tons of spirulina biomass are produced every year; nearly 70 percent is produced in China, India and Taiwan.

Food and animal feed

Photobioreactors of the facility in Klötze, Saxony-Anhalt, Germany. © Bioprodukte Prof. Steinberg GmbH

Spirulina is a blue-green cyanobacterium (ed. note: cyanobacteria were previously classified as algae), whose blue colour comes from phycocyanine. Phycocyanine is used as a dye in cosmetics and foods, for example, and also as a fluorescent dye in the biosciences. Other commercially used components of spirulina are the iron-sulphur proteins thioredoxin and ferredoxin. The quantity of spirulina used in the production of chemical compounds is negligible. As spirulina has a very high protein content (70 percent of dry matter) and is rich in vitamin B12, 97 percent of the global spirulina production is used as biomass. Applications include feed, food and food supplements. 75 percent of all spirulina products are consumed by humans. 

In addition to spirulina, chlorella are also microalgae where the lion’s share of production is used as biomass. Chlorella is also used for the production of food, food supplements and animal feed. Worldwide, chlorella producers cultivate an estimated 5,000 tons per year. A state-of-the-art production facility in the city of Klötze (Saxony-Anhalt, Germany) uses a modern photobioreactor system for the cultivation of chlorella. However, chlorella is mostly cultivated in large, open water pools, so-called open-pond systems. It seems that tradition still has its place in modern microalgae production.

Polyunsaturated fatty acids

Some microalgae species can synthesise polyunsaturated fatty acids, in particular omega-3 fatty acids, which are commonly found in marine and plant oils. Many omega-3 fatty acids are essential for the human metabolism and have to be supplied through the diet. Docosahexaenoic acid (DHA), an omega-3 fatty acid with 22 carbon (C) atoms, is for example produced from the microalgae Ulkenia and Schizochytrium. Humans can synthesise DHA, but need linolenic acid for doing so. Linolenic acid is also an essential fatty acid that must be consumed for proper health, but humans only convert a small proportion of linolenic acid into DHA. One major source of DHA is seafish. Since many people eat too little seafish, nutrition experts recommend the consumption of DHA-containing food supplements and functionalised foods. 94 percent of DHA produced from Ulkenia is used in functional food; five percent are used in food supplements and only one percent is used for animal feed.

Schizochytrium is used for the production of DHA and the polyunsaturated C20 fatty acid eicosapentaenoic acid, which is also essential for humans. Gamma-linolenic acid and arachidonic acid are also important polyunsaturated fatty acids that are extracted from algae.

Carotene and astaxanthin

Haematococcus pluvialis microalgae produce the red dye astaxanthin. © Subitec GmbH

Dyes are also important molecules that are synthesised by algae. The carotinoids beta-carotene and astaxanthin are two such dyes. Dry Dunaliella salina biomass has a beta-carotene content of up to 14 percent. The dye secures 75 percent of the turnover that algal biotechnology companies achieve with Dunaliella salina products. Total turnover achieved with Dunaliella is estimated at around 75 million US dollars, including 60 million from food supplements. 

Astaxanthin is one of the most valuable products that are isolated and processed from microalgae. One way to produce the reddish dye is with Haematococcus algae. Although the astaxanthin market is dominated by chemically synthesised astaxanthin, there is huge interest in natural astaxanthin. People are willing to pay high prices for the natural dye. The average prices for natural astaxanthin are in the range of 7,000 US dollars per kilogramme. Haematococcus algae are therefore mainly (in 90 percent of cases) used for the extraction of astaxanthin. 

Natural astaxanthin is in demand particularly from companies that only use natural compounds in their products. Customers include cosmetics manufacturers as well as food and feed producers. Around 85 percent of all astaxanthin produced is used for food supplements.

Increasing demand

Experts estimate that the material use of microalgae will rise further. Around 35,000 tons of algal dry mass are processed in the three market segments, “diet”, “food”, “cosmetics”. More than 85 percent of biomass are used in the application areas “functionalised foods” and “food supplements”. Both markets have an estimated annual sales volume of around 280 million US dollars.

For the coming years, it is likely that the material use of microalgae will increase although their importance is also growing in the energy sector. Microalgae have found their place in various markets as the providers of raw material, both as biomass and as high-quality extracts.

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