Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Department of Agricultural Biotechnology and Center for Food and Bioconvergence, Seoul National University, Seoul 08826, South Korea.
Biotechnol Adv. 2019 Mar-Apr;37(2):271-283. doi: 10.1016/j.biotechadv.2018.12.003. Epub 2018 Dec 14.
Numerous metabolic engineering strategies have allowed yeasts to efficiently assimilate xylose, the second most abundant sugar component of lignocellulosic biomass. During the investigation of xylose utilization by yeasts, a global rewiring of metabolic networks upon xylose cultivation has been captured, as opposed to a pattern of glucose repression. A clear understanding of the xylose-induced metabolic reprogramming in yeast would shed light on the optimization of yeast-based bioprocesses to produce biofuels and chemicals using xylose. In this review, we delved into the characteristics of yeast xylose metabolism, and potential benefits of using xylose as a carbon source to produce various biochemicals with examples. Transcriptomic and metabolomic patterns of xylose-grown yeast cells were distinct from those on glucose-a conventional sugar of industrial biotechnology-and the gap might lead to opportunities to produce biochemicals efficiently. Indeed, limited glycolytic metabolic fluxes during xylose utilization could result in enhanced production of metabolites whose biosynthetic pathways compete for precursors with ethanol fermentation. Also, alleviation of glucose repression on cytosolic acetyl coenzyme A (acetyl-CoA) synthesis, and respiratory energy metabolism during xylose utilization enhanced production of acetyl-CoA derivatives. Consideration of singular properties of xylose metabolism, such as redox cofactor imbalance between xylose reductase and xylitol dehydrogenase, is necessary to maximize these positive xylose effects. This review argues the importance and benefits of xylose utilization as not only a way of expanding a substrate range, but also an effective environmental perturbation for the efficient production of advanced biofuels and chemicals in yeasts.
许多代谢工程策略使酵母能够有效地同化木糖，木糖是木质纤维素生物质中第二丰富的糖组分。在研究酵母利用木糖的过程中，发现了木糖培养时代谢网络的全局重布线，而不是葡萄糖抑制模式。对酵母中木糖诱导的代谢重编程有了清晰的认识，将有助于优化基于酵母的生物工艺，以利用木糖生产生物燃料和化学品。在这篇综述中，我们深入研究了酵母木糖代谢的特点，以及以木糖作为碳源生产各种生物化学物质的潜在好处，并举例说明。与葡萄糖（工业生物技术的常规糖）相比，木糖培养的酵母细胞的转录组和代谢组模式明显不同，这种差异可能为高效生产生物化学物质提供机会。事实上，在利用木糖时，有限的糖酵解代谢通量可能导致代谢物的产量增加，这些代谢物的生物合成途径与乙醇发酵竞争前体。此外，在利用木糖时，细胞溶质乙酰辅酶 A（acetyl-CoA）合成和呼吸能量代谢中的葡萄糖抑制得到缓解，增强了乙酰辅酶 A 衍生物的产量。考虑木糖代谢的单一特性，例如木糖还原酶和木糖醇脱氢酶之间的氧化还原辅因子失衡，对于最大限度地发挥这些积极的木糖效应是必要的。这篇综述认为，利用木糖不仅是扩大底物范围的一种方式，而且是在酵母中高效生产先进生物燃料和化学品的一种有效环境扰动，具有重要性和好处。
