Time-based comparative transcriptomics in engineered xylose-utilizing Saccharomyces cerevisiae identifies...

Area of Science:

• Biotechnology
• Metabolic Engineering
• Fermentation Science

Background:

• Agricultural residues are rich in lignocellulosic materials, a viable source for pentose sugars like xylose.
• Ethanol production through consolidated bioprocessing demands microorganisms resilient to high temperatures, ethanol concentrations, and inhibitors.
• Developing robust yeast strains is crucial for efficient and cost-effective biofuel production from renewable resources.

Purpose of the Study:

• To genetically enhance Saccharomyces cerevisiae for efficient xylose utilization and ethanol production at high temperatures (38 °C).
• To investigate the transcriptomic response of yeast to high-temperature fermentation using xylose as the sole carbon source.
• To identify key genes and cellular mechanisms involved in heat stress tolerance and xylose consumption.

Main Methods:

• Genetic enhancement of an industrial Saccharomyces cerevisiae strain (sun049) for xylose uptake at high temperatures.
• Fermentation experiments using engineered yeast to produce ethanol from xylose at 38 °C.
• Comparative transcriptomics analysis of yeast under high (38 °C) versus control (30 °C) temperature conditions during early fermentation.

Main Results:

• The engineered Saccharomyces cerevisiae strain produced 13.9 g/l ethanol from 50 g/l xylose at 38 °C.
• Transcriptomic analysis revealed down-regulation of genes for amino acid, cell wall, and ribosomal protein synthesis under heat stress.
• Key genes and pathways, including hexose transporter HXT5, heat shock proteins, ubiquitin proteins, and proteolysis, were induced to enhance cell stability and xylose uptake at high temperatures.
• A correlation between high temperature and increased xylitol accumulation was observed, potentially indicating a cellular protective mechanism.

Conclusions:

• Genetic enhancement of Saccharomyces cerevisiae enables efficient xylose fermentation to ethanol at high temperatures.
• Heat stress impacts cellular processes, necessitating the induction of specific genes for thermotolerance and substrate utilization.
• Understanding these molecular mechanisms is vital for optimizing yeast strains for industrial biofuel production from lignocellulosic biomass.