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Front. Microbiol. | doi: 10.3389/fmicb.2019.01649

A Thi2p regulatory network controls the post-glucose effect of xylose utilization in Saccharomyces cerevisiae

Shan Wei1, Penggang Bai1, Yanan Liu1, Mengdan Yang Yang2, Juanzhen Ma2,  Jin Hou2,  Weifeng Liu2,  Xiaoming Bao2, 3 and  Yu Shen4*
  • 1Shandong University, China
  • 2Shandong University, China
  • 3Qilu University of Technology, China
  • 4State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Shandong University, China

The complete and efficient utilization of both glucose and xylose is necessary for the economically viable production of biofuels and chemicals using lignocellulosic feedstocks. Although recently obtained recombinant Saccharomyces cerevisiae strains metabolize xylose well when xylose is the sole carbon source in the medium (henceforth referred to as "X stage"), their xylose consumption rate is significantly reduced during the xylose-only consumption phase of glucose-xylose co-fermentation ("GX stage"). This post-glucose effect seriously decreases overall fermentation efficiency. We showed in previous work that THI2 deletion can alleviate this post-glucose effect, but the underlying mechanisms were ill-defined. In the present study, we profiled the transcriptome of a thi2Δ strain growing at the GX stage. Thi2p in GX stage cells regulates genes involved in the cell cycle, stress tolerance, and cell viability. Importantly, the regulation of Thi2p differs from a previous regulatory network that functions when glucose is the sole carbon source, which suggests that the function of Thi2p depends on the carbon source. Modeling research seeking to optimize metabolic engineering via TFs should account for this important carbon source difference. Building on our initial study, we confirmed that several identified factors did indeed increase fermentation efficiency. Specifically, overexpressing STT4, RGI2, and TFC3 increases specific xylose utilization rate of the strain by 36.9%, 29.7% and 42.8%, respectively, in the GX stage of anaerobic fermentation. Our study thus illustrates a promising strategy for the rational engineering of yeast for lignocellulosic ethanol production.

Keywords: Saccharomyces cerevisiae (Baker's yeast), Xylose metabolism, regulation of carbon metabolism, Thi2p, Anaerobic fermentation, the post-glucose effect

Received: 20 May 2019; Accepted: 03 Jul 2019.

Edited by:

Junbiao Dai, Shenzhen Institutes of Advanced Technology (CAS), China

Reviewed by:

Chaoguang Tian, Tianjin Institute of Industrial Biotechnology (CAS), China
Xinqing Zhao, Shanghai Jiao Tong University, China
Jiong Hong, University of Science and Technology of China, China  

Copyright: © 2019 Wei, Bai, Liu, Yang, Ma, Hou, Liu, Bao and Shen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Yu Shen, Shandong University, State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Qingdao, China,