One of the breakthrough discoveries for Thomas Brück and his team are yeasts that, during their growth stage, metabolise carbohydrates (sugar) into energy-rich oils rather than alcohol (ethanol), as is normally the case. This feat is accomplished by the yeast Trichosporon oleaginosus, which was isolated from a compost heap in Ireland. It is a highly unconventional yeast that can convert diverse carbohydrates into biomass and special oils. With up to 40% fatty acids, the oils produced resemble olive oil.

Trichosporon oleaginosusisn’t too choosy when it comes to food: it feasts on the waste of corn, crabs, wheat bran, wood shavings or straw, pulling out every convertible carbohydrate. “The yeast can be added to all manner of existing waste products, which ensures that production is sustainable,” says project leader Daniel Garbe. In a series of chemical metabolic steps, the yeast converts the carbohydrates into fat that it can fall back on in lean times—much like our own “padding”.

Stress triggers fat production

Normally, a single yeast cell consists of 20% fat, but in times of stress, it increases its fat reserves up to 80%. The researchers take advantage of this reaction and put the yeast on a “diet”: during its growth phase, the yeast is deprived of nitrogen and phosphate. The yeast reacts by using all its remaining energy to create emergency fat reserves. “When we view yeast under a microscope, we basically see only fats and a few cell structures,” says Thomas Brück. When the yeast reaches this point, the researchers end the “diet”. This ensures they have the highest yield because the “hungry” yeast hasn’t yet begun to resort to the fat stores for its own survival.

Profiling fatty acids

By applying the art of chemistry, fats can be transformed into just about anything. One of the research teams in the Synthetic Biotechnology group is now experimenting with a variety of fatty acid “profiles”. The team changes various parameters and observes how the yeast reacts. For example, when the researchers feed the yeast different kinds of sugar, the fatty acids produced have different profiles. And a similar effect on the profile of the fatty acids can be attained by varying the temperature or by removing sulphureous substances from the culture medium. These manipulations prompt the versatile yeast to release a different profile of the fatty acids.

How is this possible? Chemically speaking, the different fats and oils are related: they’re structured around a glycerol molecule joined to three different fatty acid units having a different number of carbon atoms. This gives rise to the term “triglyceride” for biologically produced fats and oils. Oils used as food also have many double bonds, in which case they are called polyunsaturated fats, whose antioxidant properties render them very healthy. Depending on the profile, various kinds of oil can be made from the fatty acids: oil for food (palm oil alternatives, fish oil derivatives, Omega-3 fatty acids for baby food) or the oily base for biofuels, plastics and cosmetics.

Alternatives to palm oil

To date, many plant oils are harvested from plants that are grown in environmentally detrimental monoculture and that damage or destroy the ecosystem. To produce palm oil, valuable rainforests have been cut down, depriving endangered animals such as the Orang-utan of their habitat. Palm oil, in the meantime, is an ingredient in numerous food and cosmetic products—and despite its non-ecological production, demand remains high.

“The composition of fatty acids in palm oil unfortunately can’t be produced naturally in other organisms.” This is how Norbert Mehlmer, genetic engineer at Synthetic Biotechnology, frames the problem. To find an alternative to palm oil, the researchers are resorting to new methodologies to insert a foreign gene into yeasts. As a first step, the researchers use the soil bacterium Agrobacterium tumefaciensas a door opener for the foreign gene. In a second step, the yeast culture is then treated with an antibiotic, causing the Agrobacterium tumefaciensto die. What remains is yeast with the desired genetic make-up able to produce tailor-made, high-quality fats and oils—safely, year-round and reliably.

The industrial partners of Thomas Brück’s team at Synthetic Biotechnology see great potential in two other fatty acid profiles: fish oil alternatives and linoleic acid, an Omega-3 fatty acid for baby food. “In the next five to seven years, these two oils could be ready for commercial production,” Brück says.