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Biotechnol Biofuels. 2019 Apr 23;12:97. doi: 10.1186/s13068-019-1427-6. eCollection 2019.

Evolutionary engineering in Saccharomyces cerevisiae reveals a TRK1-dependent potassium influx mechanism for propionic acid tolerance.

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1Department of Molecular Sciences, Macquarie University, Sydney, NSW 2109 Australia.
2CSIRO Synthetic Biology Future Science Platform, Canberra, ACT 2601 Australia.
3KTH School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, 106 91 Stockholm, Sweden.



Propionic acid (PA), a key platform chemical produced as a by-product during petroleum refining, has been widely used as a food preservative and an important chemical intermediate in many industries. Microbial PA production through engineering yeast as a cell factory is a potentially sustainable alternative to replace petroleum refining. However, PA inhibits yeast growth at concentrations well below the titers typically required for a commercial bioprocess.


Adaptive laboratory evolution (ALE) with PA concentrations ranging from 15 to 45 mM enabled the isolation of yeast strains with more than threefold improved tolerance to PA. Through whole genome sequencing and CRISPR-Cas9-mediated reverse engineering, unique mutations in TRK1, which encodes a high-affinity potassium transporter, were revealed as the cause of increased propionic acid tolerance. Potassium supplementation growth assays showed that mutated TRK1 alleles and extracellular potassium supplementation not only conferred tolerance to PA stress but also to multiple organic acids.


Our study has demonstrated the use of ALE as a powerful tool to improve yeast tolerance to PA. Potassium transport and maintenance is not only critical in yeast tolerance to PA but also boosts tolerance to multiple organic acids. These results demonstrate high-affinity potassium transport as a new principle for improving organic acid tolerance in strain engineering.


Adaptive laboratory evolution; Organic acid tolerance; Potassium uptake; Propionic acid; TRK1; Yeast

Conflict of interest statement

The authors declare that they have no competing interests.

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