InnCoCells uses a range of technologies for the sustainable production of cosmetic ingredients
We are using plant cell suspension cultures, aeroponic cultivation, and whole plants growing in the greenhouse and field to avoid the overharvesting of wild plants
Image credit: lychees by B. Navez (CC BY-SA 4.0)
Plant cell suspension and organ cultures
Plants are composed of millions of cells and each of those cells carries the same genetic information as the whole plant. This means in theory that whatever molecules can be made by whole plants can also be made by single cells. The cells can be cultivated aseptically in bioreactors to produce extracts or pure ingredients. However, the undifferentiated plant cells in bioreactors are sometimes unable to produce the same molecules as specialized cells in the whole plant, and it may be necessary to add extra components to the medium to persuade them. For example, we can add intermediates for conversion to the target molecules, or we can add elicitors that stimulate the cells to activate the target metabolic pathways. It may also be possible to engineer the cells to behave in different ways. The InnCoCells project will be testing cell suspension cultures derived from many different plants to see if we can produce the molecules that make the best cosmetic ingredients. As an example, the picture below shows the appearance of tomato cells under a microscope.
How do you make plant cell suspension cultures? The first step is to cut off a small piece of plant tissue, such as part of a leaf, and expose it to a medium containing plant hormones that cause the cells to return to a basal, undifferentiated state known as a callus. The picture below shows callus tissue producing molecules that confer different colours. Callus can be persuaded to produce roots and shoots if the hormone balance is changed again. Alternatively, the cells can be separated to make a cell suspension culture that can be grown in large vats.
Another way to make plant cells produce specific target metabolites is the induction of hairy root cultures. This involves the use of a natural soil pathogen that infects the roots and colonizes them, causing rapid and unregulated growth (resulting in many additional root hairs, hence the name “hairy roots”). Hairy roots can be grown independently and indefinitely in culture, allowing the continuous production of valuable metabolites. Although hairy roots cannot be cultivated at the same scale as plant cell suspension cultures, they remain stable for longer in culture and produce more biomass, which maximizes their ability to produce target compounds.
Aeroponics means the cultivation of plants in the air, so that the roots are exposed rather than embedded in soil or another medium. Aeroponics is a useful cultivation method because many plants secrete proteins and metabolites from their roots, and these molecules are easier to recover if the roots are exposed. Plants are usually irrigated by applying water and nutrients to the soil, but in aeroponic cultivation water and nutrients are sprayed on the roots as a mist. Exposure to the air also increases the availability of oxygen to the roots.
In the InnCoCells project, the aeroponic cultivation of plants will allow us to collect root exudates. Molecules exuded from roots are usually absorbed by the soil or dispersed in water, but aeroponics allows the exudate droplets to be collected, together with any valuable molecules they contain.
Cultivation in the greenhouse and field
The final upstream production strategy we are using in the InnCoCells project is the cultivation of plants in greenhouses or in the open field. This is similar to conventional agriculture although we will be harvesting the plants to extract cosmetic ingredients rather than food, feed, fuel or materials as would be the case for typical crops. The pictures below show the cultivation and harvesting of marigold, a source of many valuable metabolites.
Cultivation in the greenhouse or field is only possible when a plant has been domesticated (adapted to agricultural conditions) and this is a useful strategy to avoid the overharvesting of wild species. However, domestication can sometimes alter the properties of plants, including the characteristics that prompted domestication in the first place. So the InnCoCells project will be experimenting with different agricultural conditions to optimize the production of cosmetic ingredients.
The harvested plants can then be sent to other partners in the InnCoCell consortium for downstream processing and ingredient testing.