Membrane Fluidity of Saccharomyces cerevisiae from
            <i>Huangjiu</i>
            (Chinese Rice Wine) Is Variably Regulated by
            <i>OLE1</i>
            To Offset the Disruptive Effect of Ethanol

Cheng

et al. 2020

Biotechnol Biofuels

Background Product toxicity is one of the bottlenecks for microbial production of biofuels, and transporter-mediated biofuel secretion offers a promising strategy to solve this problem. As a robust microbial host for industrial-scale production of biofuels, Saccharomyces cerevisiae contains a powerful transport system to export a wide range of toxic compounds to sustain survival. The aim of this study is to improve the secretion and production of the hydrophobic product (β-carotene) by harnessing endogenous ABC transporters combined with physiological engineering in S. cerevisiae. Results Substrate inducibility is a prominent characteristic of most endogenous transporters. Through comparative proteomic analysis and transcriptional confirmation, we identified five potential ABC transporters (Pdr5p, Pdr10p, Snq2p, Yor1p, and Yol075cp) for β-carotene efflux. The accumulation of β-carotene also affects cell physiology in various aspects, including energy metabolism, mitochondrial translation, lipid metabolism, ergosterol biosynthetic process, and cell wall synthesis. Here, we adopted an inducible GAL promoter to overexpress candidate transporters and enhanced the secretion and intracellular production of β-carotene, in which Snq2p showed the best performance (a 4.04-fold and a 1.33-fold increase compared with its parental strain YBX-01, respectively). To further promote efflux capacity, two strategies of increasing ATP supply and improving membrane fluidity were following adopted. A 5.80-fold increase of β-carotene secretion and a 1.71-fold increase of the intracellular β-carotene production were consequently achieved in the engineered strain YBX-20 compared with the parental strain YBX-01. Conclusions Overall, our results showcase that engineering endogenous plasma membrane ABC transporters is a promising approach for hydrophobic product efflux in S. cerevisiae. We also highlight the importance of improving cell physiology to enhance the efficiency of ABC transporters, especially energy status and cell membrane properties.

Section: Resultsmentioning

confidence: 99%

Section: Improving Membrane Fluidity To Enhance β-Carotene Secretionmentioning

confidence: 99%

Engineering endogenous ABC transporter with improving ATP supply and membrane flexibility enhances the secretion of β-carotene in Saccharomyces cerevisiae

Cheng

et al. 2020

Biotechnol Biofuels

“…Interestingly, we also found the cell volume of G14 was moderately smaller than the parent. Other researchers have found that the composition change in membrane [ 34 ] or cell wall [ 35 ] is generally associated with the improvement of stress tolerance in industrial strains. Therefore, we inferred that the cell membrane composition and cell wall composition were changed in the G14.…”

Section: Resultsmentioning

confidence: 99%

Augmented peroxisomal ROS buffering capacity renders oxidative and thermal stress cross-tolerance in yeast

et al. 2021

Microb Cell Fact

Background Thermotolerant yeast has outstanding potential in industrial applications. Komagataella phaffii (Pichia pastoris) is a common cell factory for industrial production of heterologous proteins. Results Herein, we obtained a thermotolerant K. phaffii mutant G14 by mutagenesis and adaptive evolution. G14 exhibited oxidative and thermal stress cross-tolerance and high heterologous protein production efficiency. The reactive oxygen species (ROS) level and lipid peroxidation in G14 were reduced compared to the parent. Oxidative stress response (OSR) and heat shock response (HSR) are two major responses to thermal stress, but the activation of them was different in G14 and its parent. Compared with the parent, G14 acquired the better performance owing to its stronger OSR. Peroxisomes, as the main cellular site for cellular ROS generation and detoxification, had larger volume in G14 than the parent. And, the peroxisomal catalase activity and expression level in G14 was also higher than that of the parent. Excitingly, the gene knockdown of CAT encoding peroxisomal catalase by dCas9 severely reduced the oxidative and thermal stress cross-tolerance of G14. These results suggested that the augmented OSR was responsible for the oxidative and thermal stress cross-tolerance of G14. Nevertheless, OSR was not strong enough to protect the parent from thermal stress, even when HSR was initiated. Therefore, the parent cannot recover, thereby inducing the autophagy pathway and resulting in severe cell death. Conclusions Our findings indicate the importance of peroxisome and the significance of redox balance in thermotolerance of yeasts.

“…The integrity of cell membranes has also attracted much attention. For example, Yang et al [109] found that S. cerevisiae strain with increasing content of unsaturated fatty acid (UFA) and cell membrane fluidity can tolerate high concentrations (up to 25 vol%) of ethanol. Researchers have found that the increasing content of some amino acids helps yeast to resist environmental stresses.…”

Section: Evident Correlation Among Functional Factorsmentioning

confidence: 99%

Overview of yeast environmental stress response pathways and the development of tolerant yeasts

Syst Microbiol and Biomanuf

2021

Yeast is widely used for industrial production of various types of products, such as ethanol and enzymes. However, its fermentation efficiency is strongly reduced by harmful environmental stresses. Specifically, harmful environmental stresses damage important cellular components, such as cell wall, cell membrane, proteins, etc. Then, these damages cause cellular metabolic disorders or even death. In the past decades, there has been a portfolio of studies on the environmental stress tolerance of yeasts, which mainly aimed at cell damages caused by different environmental stresses, different ways to improve yeast environmental stress tolerance or a tolerance mechanism for certain environmental stress. However, a comprehensive overview of how yeasts respond to environmental stresses is lacking, and the correlation of tolerance mechanism between different environmental stresses is unclear. In this review, we summarized the general damages induced by most of environmental stresses, the existing major mechanisms of environmental stress tolerance from the perspective of key signalling pathways, and the common ways to improve the resistance to environmental stresses in yeast cells. The tolerance mechanisms of yeast cells to different environmental stresses are diverse, but sometimes they share the same signalling pathway. Cells use sensors on the cell surface to recognize environmental stresses and transmit signals to the nucleus to cause changes in gene expression. By summarizing the main signalling pathways, including MAPK pathway, cAMP/PKA pathway, YAP1/ SKN7 pathway, it will provide a powerful reference for future efforts to promote yeast environmental stress tolerance and study yeast tolerance mechanisms.