Feb 19, 2007

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Physical containment

Underground cultivation

Genetically modified plants that produce pharmaceutical substances are not allowed to spread or enter the food and feed chain. In order to ensure that they don’t, these kinds of plant can be cultivated in closed systems. In North America disused mines are being used for this purpose.

GM plants are generally kept under containment conditions for several years during their long development phase: first in the climate chamber, later in dedicated greenhouses. Only then are they released into the open, initially with safety requirements, which are gradually relaxed if it is seen that the plants do not pose a risk to the environment.

Disused mine in Marengo (Indiana/USA) used for the cultivation of plants under controlled conditions. Left: entrance to one of the plant chambers.

Containment: Inside a plant chamber.

Photos: Purdue University; Ag Communications

People are now considering whether certain GM plants, particularly those that produce pharmaceuticals, should not be released at all, but cultivated instead in closed systems with no direct contact with the environment.

• This would make it possible to rule out to a large extent the possibility of the plants or transgenes spreading.
• Conditions in closed systems are easier to control than in the open. This makes it possible not only to obtain higher yields of the pharmaceutical products, but also to achieve the high quality standards necessary for the production of pharmaceuticals.

Closed systems for the cultivation of plants include more than just greenhouses and climate chambers. For several years now, former copper, zinc and limestone mines in the USA and Canada have also been used for this purpose. Since 1991 a Canadian company has been conducting cultivation experiments under artificial light 360 metres below ground in a mine measuring several hundred hectares. The trials involve over five hundred different plant species, including tobacco, yew trees, maize, oilseed rape and poplars. These are not all transgenic plants – the company also supplies the Canadian government with marijuana for pharmaceutical purposes.

In the USA two companies are using disused mines for the contained underground cultivation of plants. Cultivation experiments with (non-transgenic) maize plants carried out in collaboration with researchers from Purdue University showed that it was possible to harvest more than twice as much maize under the artificial conditions underground than the US average. This is because where there is complete control over the cultivation conditions the plants can grow in a stress-free environment – no fluctuations in temperature or air humidity, no insects, no pathogenic fungi or viruses. The plants can put all their energy into growing.

Now that the regulations for releasing pharma plants have been tightened up in the USA and Canada, underground cultivation is opening up new possibilities for molecular pharming. From the perspective of the companies, mines are especially attractive because the administrative effort and costs for approval of the GM plants are very low or non-existent. Controlling the production conditions is much easier underground than in the field. Compared with a greenhouse, mines are also cheaper in terms of energy: In the greenhouse a lot of energy goes into offsetting temperature fluctuations. Temperatures in the mines are constant.