Yeast cells are remarkable. They can be used as model systems for added knowledge about human cells; almost everything found in yeast is actually also found in humans. Furthermore, they can be used as small, efficient, factories for producing fuels and chemicals of various kinds.
Research on yeast is conducted at the Department of Biology and Biological Engineering at Chalmers, where two major breakthroughs recently was published in prestigious research journals. Both projects have succeeded in altering the metabolism of the yeast cells, thereby significantly improving their potential as cell factories.Producing fatty acids
In one of the studies – published in Cell – the research team rewired the cell metabolism, making it produce large quantities of free fatty acids instead of ethanol, which it normally produces. The fatty acids can be used for example in manufacturing of detergents, lubricants, cosmetics, and pharmaceutical ingredients.
– We achieved the highest production level of free fatty acids by fermentation ever, says Tao Yu, postdoc at the division of Systems and Synthetic Biology.
The metabolic network of the yeast cell is tightly regulated to maintain metabolic homeostasis, thereby protecting the cell from environmental perturbations. Consequently, it is challenging to alter, and the research proving it possible to achieve this high yield of fatty acid is therefore to be considered as a major breakthrough.
– Our work demonstrates that despite millions of years of evolution, the metabolism of yeast – Saccharomyces cerevisiae
– is remarkably plastic, says Tao Yu.
– Engineering microbes, like yeast, for the production of fuels and chemicals enables the replacement of fossil based production. It thereby supports the growing population and economy with a lower carbon footprint.More efficient without the Crabtree effect
The other study, published in Nature Communications, prove it possible to modify the metabolism of yeast to abolish the so called Crabtree effect. The Crabtree effect, named after the biochemist Herbert Crabtree, is a phenomenon which ensures the advantage of yeast in its ecological niche by rapidly consuming glucose and producing ethanol. On the other hand, this effect also makes it harder to make the cell produce anything else but ethanol. Abolishing the Crabtree effect is a true challenge, as it requires a global rewiring of the entire metabolic network.
– There is much interest in doing this, as a yeast cell without the Crabtree effect is able to produce much higher yields of target products such as pharmaceuticals, chemicals and biofuels, says Zongjie Dai, a visiting researcher at Systems and Synthetic Biology.
– This study created a platform strain with high potential. Additionally, our findings may give an insight into cancer cell metabolism due to the similarity between the Crabtree effect and the Warburg effect in cancer cells.
The next steps for Zongjie Dai include combining adaptive laboratory evolution with systems biology, to get further knowledge about the new yeast.
– I will also take advantage of this novel platform strain, and produce bulk and fine chemicals as well as biofuels with higher yield.
Tao Yu will further couple the cell growth to the free fatty acid producing pathway.
– And we will further improve the yield of free fatty acids by metabolic engineering, he concludes.
Text: Mia Malmstedt
Photo: Martina Butorac