Wei Shan, Bai Penggang, Liu Yanan, Yang Mengdan, Ma Juanzhen, Hou Jin, Liu Weifeng, Bao Xiaoming, Shen Yu
State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Shandong University, Qingdao, China.
Shandong Provincial Key Laboratory of Microbial Engineering, Qi Lu University of Technology, Jinan, China.
Front Microbiol. 2019 Jul 17;10:1649. doi: 10.3389/fmicb.2019.01649. eCollection 2019.
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 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 deletion can alleviate this post-glucose effect, but the underlying mechanisms were ill-defined. In the present study, we profiled the transcriptome of a Δ 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 , and increases specific xylose utilization rate of the strain by 36.9, 29.7, 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.
利用木质纤维素原料经济可行地生产生物燃料和化学品，需要完全且高效地利用葡萄糖和木糖。尽管最近获得的重组菌株在木糖是培养基中唯一碳源时（以下简称“X阶段”）能很好地代谢木糖，但在葡萄糖-木糖共发酵的仅木糖消耗阶段（“GX阶段”），它们的木糖消耗速率会显著降低。这种葡萄糖后效应严重降低了整体发酵效率。我们在之前的工作中表明，基因缺失可以减轻这种葡萄糖后效应，但其潜在机制尚不明确。在本研究中，我们分析了在GX阶段生长的Δ菌株的转录组。GX阶段细胞中的Thi2p调节参与细胞周期、应激耐受性和细胞活力的基因。重要的是，Thi2p的调节不同于葡萄糖是唯一碳源时起作用的先前调控网络，这表明Thi2p的功能取决于碳源。旨在通过转录因子优化代谢工程的建模研究应考虑到这一重要的碳源差异。基于我们的初步研究，我们证实了几个已确定的因素确实提高了发酵效率。具体而言，在厌氧发酵的GX阶段，过表达、和分别使菌株的木糖比利用率提高了36.9%、29.7%、42.8%。因此，我们的研究说明了一种为木质纤维素乙醇生产对酵母进行合理工程改造的有前景的策略。
