Engineering prokaryotic regulator IrrE to enhance stress tolerance in budding yeast

Abstract

Background: Stress tolerance is one of the important desired microbial traits for industrial bioprocess and global regulatory protein engineering is an efficient approach to improve strain tolerance. In our study, IrrE, a global regulatory protein from prokaryotic organism Deinococcus radiodurans, was engineered to confer yeast the improved tolerance to the inhibitors in lignocellulose hydrolysates or high temperature.Results: Three IrrE mutants were developed through directed evolution and the expression of these mutants could improve the yeast fermentation rate by 3- to 4-fold in the presence of multiple inhibitors. Subsequently, the tolerance to multiple inhibitors of single-site mutants based on the mutations from the variants was then evaluated, and eleven mutants including L65P, I103T, E119V, L160F, P162S, M169V, V204A, R244G, Base 824 Deletion, V299A and A300V were identified to be critical for the improved FAP tolerance. Further studies indicated that IrrE caused genome-wide transcriptional perturbation in yeast, and the mutant I24 led to the rapid growth of Saccharomyces cerevisiae mainly by regulating the transcription level of transcription activators/factors, protecting the intracellular environment and enhancing the antioxidant capacity under inhibitor environment, which reflected the plasticity of IrrE. Meanwhile, we observed that the expression of the wild-type or mutant IrrE could also protect Saccharomyces cerevisiae from the damage caused by thermal stress. The recombinant yeast strains were able to grow with glucose at 42 ºC.Conclusions: IrrE from Deinococcus radiodurans can be engineered as a tolerance-enhancer for Saccharomyces cerevisiae. Systematic research on the regulatory model and mechanism of a prokaryotic global regulatory factor IrrE to increase yeast tolerance provided valuable insights for the improvement of microbial tolerance to complex industrial stress conditions.

Recent advances in yeast genome evolution with stress tolerance for green biological manufacturing

“…Prokaryotic molecular elements may also be employed in the yeast for enhanced thermotolerance. In one study, directed evolution‐derived mutants of global regulatory protein (IrrE) from Deinococcus radiodurans and their integration in yeast revealed enhanced thermotolerance (L. Wang et al, 2020). In addition, wild‐type or mutant IrrE expression in S. cereviseae may also protect the strain from the damage caused by thermal stress (L. Wang et al, 2020), suggesting its significance in enhancement of thermotolerance under stress conditions.…”