Response mechanisms of Saccharomyces cerevisiae to the stress factors present in lignocellulose hydrolysate and strategies for constructing robust strains

Abstract

Bioconversion of lignocellulosic biomass to biofuels such as bioethanol and high value-added products has attracted great interest in recent decades due to the carbon neutral nature of biomass feedstock. However, there are still many key technical difficulties for the industrial application of biomass bioconversion processes. One of the challenges associated with the microorganism Saccharomyces cerevisiae that is usually used for bioethanol production refers to the inhibition of the yeast by various stress factors. These inhibitive effects seriously restrict the growth and fermentation performance of the strains, resulting in reduced bioethanol production efficiency. Therefore, improving the stress response ability of the strains is of great significance for industrial production of bioethanol. In this article, the response mechanisms of S. cerevisiae to various hydrolysate-derived stress factors including organic acids, furan aldehydes, and phenolic compounds have been reviewed. Organic acids mainly stimulate cells to induce intracellular acidification, furan aldehydes mainly break the intracellular redox balance, and phenolic compounds have a greater effect on membrane homeostasis. These damages lead to inadequate intracellular energy supply and dysregulation of transcription and translation processes, and then activate a series of stress responses. The regulation mechanisms of S. cerevisiae in response to these stress factors are discussed with regard to the cell wall/membrane, energy, amino acids, transcriptional and translational, and redox regulation. The reported key target genes and transcription factors that contribute to the improvement of the strain performance are summarized. Furthermore, the genetic engineering strategies of constructing multilevel defense and eliminating stress effects are discussed in order to provide technical strategies for robust strain construction. It is recommended that robust S. cerevisiae can be constructed with the intervention of metabolic regulation based on the specific stress responses. Rational design with multilevel gene control and intensification of key enzymes can provide good strategies for construction of robust strains. Graphical Abstract

Comparative chemical genomic profiling across plant-based hydrolysate toxins reveals widespread antagonism in fitness contributions

“…Several studies have investigated the response to particular hydrolysate toxins, including phenolic compounds (Fletcher and Baetz 2020 ), ionic liquids (Kumari et al 2020 ), or various other classes of compounds (Jönsson and Martín 2016 , Kim 2018 , Li et al 2022 ). Yet much remains unknown about mechanisms of toxicity and how to overcome them, especially for sets of toxins variably found together and under anaerobic conditions, which is preferred for the industrial production of fermentative biofuels.…”

Differential Protein Expression in Set5p-Mediated Acetic Acid Stress Response and Novel Targets for Engineering Yeast Stress Tolerance

“…1,2 However, the presence of inhibitors in lignocellulosic hydrolysate repress the performance of yeast, causing low fermentation efficiency. 3 One of the main inhibitors is acetic acid which is mainly generated during the pretreatment of hemicellulose, and the concentration of acetic acid may reach as high as 11 g/L. 4 The toxicity of acetic acid on yeast may be shown in multiple aspects, such as disruption of chromatin homeostasis, acidification of the internal environment, and ATP deficiency, as well as the excessive accumulation of reactive oxygen species (ROS), which results in oxidative stress.…”

“…Sustainable bioproduction using lignocellulosic biomass has received worldwide attention. The budding yeast Saccharomyces cerevisiae is widely studied for the production of cellulosic ethanol and biobased chemicals. , However, the presence of inhibitors in lignocellulosic hydrolysate repress the performance of yeast, causing low fermentation efficiency . One of the main inhibitors is acetic acid which is mainly generated during the pretreatment of hemicellulose, and the concentration of acetic acid may reach as high as 11 g/L .…”

High-pressure microwave-assisted pretreatment of softwood, hardwood and non-wood biomass using different solvents in the production of cellulosic ethanol

“…furfural from xylose or 5-(hydroxymethyl) furfural (5-HMF) from glucose. These compounds are undesirable in larger concentrations since they are considered fermentation inhibitors negatively affecting the activity of yeast [ 11 , 12 ]. In addition, the intense thermobaric processing makes the process more cost-intensive.…”