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- Pereira, Rui, 1986, et al.
(author)
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Adaptive laboratory evolution of tolerance to dicarboxylic acids in Saccharomyces cerevisiae
- 2019
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In: Metabolic Engineering. - : Elsevier BV. - 1096-7176 .- 1096-7184. ; 56, s. 130-141
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Journal article (peer-reviewed)abstract
- Improving the growth phenotypes of microbes in high product concentrations is an essential design objective in the development of robust cell factories. However, the limited knowledge regarding tolerance mechanisms makes rational design of such traits complicated. Here, adaptive laboratory evolution was used to explore the tolerance mechanisms that Saccharomyces cerevisiae can evolve in the presence of inhibiting concentrations of three dicarboxylic acids: glutaric acid, adipic acid and pimelic acid. Whole-genome sequencing of tolerant mutants enabled the discovery of the genetic changes behind tolerance and most mutations could be linked to the up-regulation of multidrug resistance transporters. The amplification of QDR3, in particular, was shown to confer tolerance not only to the three dicarboxylic acids investigated, but also towards muconic acid and glutaconic acid. In addition to increased acid tolerance, QDR3 overexpression also improved the production of muconic acid in the context of a strain engineered for producing this compound.
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2. |
- Pereira, Rui, 1986, et al.
(author)
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Elucidating aromatic acid tolerance at low pH in Saccharomyces cerevisiae using adaptive laboratory evolution
- 2020
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117:45, s. 27954-27961
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Journal article (peer-reviewed)abstract
- Toxicity from the external presence or internal production of compounds can reduce the growth and viability of microbial cell factories and compromise productivity. Aromatic compounds are generally toxic for microorganisms, which makes their production in microbial hosts challenging. Here we use adaptive laboratory evolution to generate Saccharomyces cerevisiae mutants tolerant to two aromatic acids, coumaric acid and ferulic acid. The evolution experiments were performed at low pH (3.5) to reproduce conditions typical of industrial processes. Mutant strains tolerant to levels of aromatic acids near the solubility limit were then analyzed by whole genome sequencing, which revealed prevalent point mutations in a transcriptional activator (Aro80) that is responsible for regulating the use of aromatic amino acids as the nitrogen source. Among the genes regulated by Aro80, ESBP6 was found to be responsible for increasing tolerance to aromatic acids by exporting them out of the cell. Further examination of the native function of Esbp6 revealed that this transporter can excrete fusel acids (byproducts of aromatic amino acid catabolism) and this role is shared with at least one additional transporter native to S. cerevisiae (Pdr12). Besides conferring tolerance to aromatic acids, ESBP6 overexpression was also shown to significantly improve the secretion in coumaric acid production strains. Overall, we showed that regulating the activity of transporters is a major mechanism to improve tolerance to aromatic acids. These findings can be used to modulate the intracellular concentration of aromatic compounds to optimize the excretion of such products while keeping precursor molecules inside the cell.
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