Zhu Yixuan, Zhang Jingtao, Zhu Lang, Jia Zefang, Li Qi, Xiao Wei, Cao Limin
Key Laboratory of Plant Gene Resources and Biotechnology for Carbon Reduction and Environmental Improvement, College of Life Sciences, Capital Normal University, Beijing, China.
China Center of Industrial Culture Collection, Beijing, China.
Front Bioeng Biotechnol. 2021 Feb 26;9:639595. doi: 10.3389/fbioe.2021.639595. eCollection 2021.
Xylose is the second most abundant sugar in lignocellulose, but it cannot be used as carbon source by budding yeast . Rational promoter elements engineering approaches were taken for efficient xylose fermentation in budding yeast. Among promoters surveyed, exhibited the best performance. The promoter is suppressed in the presence of glucose and derepressed by xylose, making it a promising candidate to drive xylose metabolism. However, simple ectopic expression of both key xylose metabolic genes and by the promoter resulted in massive accumulation of the xylose metabolic byproduct xylitol. Through the -driven expression of a reported redox variant, , along with optimized expression of and the downstream pentose phosphate pathway genes, a balanced xylose metabolism toward ethanol formation was achieved. Fermented in a culture medium containing 50 g/L xylose as the sole carbon source, xylose is nearly consumed, with less than 3 g/L xylitol, and more than 16 g/L ethanol production. Hence, the combination of an inducible promoter and redox balance of the xylose utilization pathway is an attractive approach to optimizing fuel production from lignocellulose.
木糖是木质纤维素中含量第二丰富的糖类，但芽殖酵母不能将其用作碳源。为了在芽殖酵母中实现高效木糖发酵，采用了合理的启动子元件工程方法。在所研究的启动子中，[具体启动子名称未给出]表现出最佳性能。该启动子在葡萄糖存在时受到抑制，而在木糖作用下解除抑制，这使其成为驱动木糖代谢的一个有潜力的候选者。然而，仅通过该启动子简单异位表达关键木糖代谢基因[基因名称未给出]和[基因名称未给出]，会导致木糖代谢副产物木糖醇大量积累。通过该启动子驱动报道的氧化还原变体[变体名称未给出]的表达，以及[基因名称未给出]和下游磷酸戊糖途径基因的优化表达，实现了向乙醇生成的平衡木糖代谢。在以50 g/L木糖作为唯一碳源的培养基中发酵时，木糖几乎被消耗殆尽，木糖醇含量低于3 g/L，乙醇产量超过16 g/L。因此，诱导型启动子与木糖利用途径的氧化还原平衡相结合，是优化从木质纤维素生产燃料的一种有吸引力的方法。
