Credit: Colourbox

Baker’s yeast could pave the way for fossil-free plastic production

Friday 11 Oct 19

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Irina Borodina
Senior Researcher
DTU Biosustain
+45 45 25 80 20

Acrylic acid

• Today, approximately 50-75 per cent of all acrylic acid converted into superabsorbent polymers, e.g. sodium polyacrylate, which is the absorbent material used in sanitary towels and nappies. The polymers are formed into little jelly balls that can absorb up to 100 times their own weight.

• Acrylic acid is also used to make paint, which is almost always acrylic-based. The substance polymerizes easily to form a fine surface that is sturdy and does not peel.

• Acrylic acid is also to make plexiglas, which is used in monitors, aquariums, contact lenses, dentures, etc. 

Ordinary baker’s yeast can be genetically engineered to produce an acid known as 3HP. This acid can be converted into acrylic acid, which, among other things, is used in the production of clear plastic.

Acrylic acid is a substance in high demand in the chemical industry because it is used to produce transparent types of plastic such as monitors, aquariums, contact lenses, dentures, and more. According to a study by market research and consulting company Grand View Research, the acrylic acid market will surpass USD 22 billion with an annual demand of almost nine million tonnes by 2022.

Today, acrylic acid is produced from gas and oil. But with the help of gene technology, yeast cells, and biomass such as sugar, the production of acrylic plastic can become fossil free, according to the findings of a research group at DTU Biosustain headed by Senior Researcher Irina Borodina. 

Improving the yeast
Using gene manipulation, the research group managed to make yeast cells produce 3-hydroxypropionic acid, or 3HP. This acid can be converted into acrylic acid when dehydrated, which is a relatively simple and inexpensive chemical process. The group based their work on two existing production pathways within the yeast cell which they ‘extended’ with enzymes from other organisms. They found these enzymes in red flour beetles and in bacteria such as E. coli and Bacillus cereus. Once the researchers had built the production pathways in the cell, they diverted the yeast cell’s metabolism to ensure that the cell produced as much 3HP as possible instead of using its energy to make other substances. 

After three years, the research group had developed a yeast strain that could produce 44 g/L of 3HP. “We’ve shown that it’s possible. Now it’s up to the companies to take the technology even further,” says Irina Borodina. 

In order to be commercially interesting, the yeast strains need to be able to produce up to 200 g/L of 3HP. Finetuning the yeast strains to the point where they can produce that much 3HP requires an investment in further development, but according to Irina Borodina it is entirely possible.

Sugar more expensive than oil
While the DTU Biosustain research group developed the new technology, several major enzyme and chemical companies also produced 3HP biologically in both yeast and E. coli, albeit using slightly different methods.

"We’ve shown that it’s possible. Now it’s up to the companies to take the technology even further"
SENIOR SCIENTIST IRINA BORODINA, DTU BIOSUSTAIN

However, it will be hard for the biologically produced 3HP to compete with the fossil-based production in terms of price, as the generally low oil prices put a spoke in the wheel of the green transition, according to Irina Borodina: 

“It’s unfair competition. The oil industry can sell the chemicals even cheaper than they do today and still make a profit, while the biomanufacturers hardly make any profit.”

The major challenge is that the microbes need food in the form of a biomass such as sugar in order to produce biochemicals. Sugar production requires a farmer to sow, fertilize, harvest, and process the biomass, which means that sugar ends up being twice as expensive as oil.

“But if we factor in the damage to the environment, climate, and health caused by oil-based chemicals and fuels and add these costs to the price, oil-based chemicals and fuels should be much more expensive—and then it would be worthwhile to use bio-based products,” says Irina Borodina.