Science - February 16, 2011

Alga produces food supplement under stress

The single cell alga Dunaliella salina can produce large amounts of the nutritive orange pigment, beta-carotene. But it only does this under great stress, as the doctoral research work of Packo Lamers shows.

An orange alga (under stress) and a green alga.
Dunaliella salina is a resilient alga, one of the few organisms which can be found in the Dead Sea. This salt-tolerant alga is usually green in colour but becomes orange under stressful circumstances, such as not enough nitrogen or too much light. 'In such cases, an imbalance exists between the energy supply from the outside and the energy which the alga uses', says Lamers. 'The alga overcomes this by making a lot of beta-carotene. This works like a sunscreen.'
Excessive light
Lamers exposed the alga to all kinds of stressful circumstances in the laboratory to find out when it could produce the most beta-carotene. Both excessive light and a shortage of nitrogen resulted in the highest production. The alga then produced ten times as much beta-carotene per hour as what alga farmers in Israel and Australia are now aware of.
Beta-carotene is a natural colouring agent used in food substances. It is also an antioxidant. This nutritive property is the reason why beta-carotene is used in food supplements. The alga is currently being cultivated in ponds with salt water in warm countries such as Israel, India and Australia. Lamers cultivated the alga under ideal circumstances with artificial light in the laboratory. 'That is much too expensive for commercial production', he says. 'Free sunlight is required.' Further research is needed to find out if the high beta-carotene production in the laboratory can also be achieved in practice.
Secondary metabolism
During his research, Lamers worked with the Bioscience department of Plant Research International. His research project arose from a Vici grant awarded to his supervisor, René Wijffels, by the Netherlands Organization for Scientific Research (NWO). Lamers' co-workers found out how to produce large quantities of algae, what the best design is for the bioreactor used to cultivate algae, and how to effectively filter the right alga products from the alga mass. Lamers focused on the secondary metabolism: how the alga produces as much of a useful substance as possible and which cellular mechanisms are involved.
Packo Lamers graduated on 11 February under RenĂ© Wijffels, professor of  Bioprocess Technology and Raoul Bino, professor of Plant Metabolomics.