Quantification and Molecular Analysis of Antagonism between Xylose Utilization and Acetic Acid Tolerance in Glucose/Xylose Cofermentation Saccharomyces cerevisiae Strains

For bioethanol production from lignocellulosic materials,
an ideal
microorganism must possess both excellent xylose utilization and a
high tolerance to inhibitory compounds. However, these two traits
often exhibit antagonism in recombinant xylose-utilizing Saccharomyces cerevisiae strains. In this study,
we developed a quantitative metric using an aggregated parameter to
evaluate the degree of this antagonism and applied it to evaluate
the antagonism of three strains (LF1, LF1-6M, and 6M-15), which had
been iteratively evolved in xylose and hydrolyzate environments. Transcriptomic
analysis revealed that the yeast strain elevates the alert level to
stresses related to DNA replication, unfolded protein, starvation,
and hyperosmosis, and reduces the uptake of unimportant nutrients
to have a higher acetic acid tolerance during adaptive evolution in
hydrolyzate. Additionally, the Snf1p-Mig1p signaling pathway was reprogrammed,
enabling the strain to utilize xylose more efficiently during adaptive
evolution in xylose. We also confirmed that disruption of the glyceraldehyde-3-phosphate
dehydrogenase gene TDH1 significantly shortened the
time required for glucose and/or xylose cofermentation under acetic
acid stress by reducing reactive oxygen species accumulation and increasing
ATP production. This study offers valuable insights for developing
robust and efficient S. cerevisiae strains
capable of glucose/xylose cofermentation.