Crabtree/Warburg-like aerobic xylose fermentation by engineered Saccharomyces cerevisiae
Crabtree/Warburg-like aerobic xylose fermentation by engineered Saccharomyces cerevisiae
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DOI：
10.1016/j.ymben.2021.09.008
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发表时间：
2021-10-04
影响因子：
8.4
通讯作者：
Sato, Trey K.
中科院分区：
文献类型：
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作者：
Lee, Sae-Byuk;Tremaine, Mary;Sato, Trey K.
木糖高效转化为经济高效的生物燃料的瓶颈限制了植物木质纤维素作为可再生原料的广泛应用。酿酒酵母将葡萄糖发酵成乙醇，其代谢通量如此之高，以至于它在有氧条件下发酵出高浓度的葡萄糖，这种特性称为克拉布特里/瓦尔堡效应。与葡萄糖相反，大多数工程化的S。酿酒酵母菌株不能以经济上可行的速率和产率发酵木糖，并且它们需要呼吸作用以获得足够的木糖代谢通量和能量返回用于有氧生长。在这里，我们进化出了呼吸缺陷型S。酿酒酵母菌株，可以在木糖上生长并将其有氧发酵为乙醇，这一特征类似于葡萄糖的克拉布特里/瓦尔堡效应。通过基因组序列比较和定向工程，我们确定了编码工程木糖代谢酶的基因的重复，以及编码戊糖磷酸途径中的转酮醇酶的基因TKL 1，是进化表型的致病遗传变化。这些酶的再工程复制，结合HOG 1，ISU 1，GRE 3和IRA 2中的缺失突变，增加了好氧和厌氧木糖发酵的速率。重要的是，我们发现这些遗传修饰在另一种遗传背景下起作用，并增加了工业相关柳枝稷水解产物中木糖转化为乙醇的速率和产量，这表明这些特定的遗传修饰可能使酵母可持续生产工业生物燃料成为可能。我们提出了一个模型，如何关键调控突变总理酵母好氧木糖发酵通过降低溢流代谢的阈值，允许突变增加木糖通量，并将其重定向到发酵产物。
Bottlenecks in the efficient conversion of xylose into cost-effective biofuels have limited the widespread use of plant lignocellulose as a renewable feedstock. The yeast Saccharomyces cerevisiae ferments glucose into ethanol with such high metabolic flux that it ferments high concentrations of glucose aerobically, a trait called the Crabtree/Warburg Effect. In contrast to glucose, most engineered S. cerevisiae strains do not ferment xylose at economically viable rates and yields, and they require respiration to achieve sufficient xylose metabolic flux and energy return for growth aerobically. Here, we evolved respiration-deficient S. cerevisiae strains that can grow on and ferment xylose to ethanol aerobically, a trait analogous to the Crabtree/Warburg Effect for glucose. Through genome sequence comparisons and directed engineering, we determined that duplications of genes encoding engineered xylose metabolism enzymes, as well as TKL1, a gene encoding a transketolase in the pentose phosphate pathway, were the causative genetic changes for the evolved phenotype. Reengineered duplications of these enzymes, in combination with deletion mutations in HOG1, ISU1, GRE3, and IRA2, increased the rates of aerobic and anaerobic xylose fermentation. Importantly, we found that these genetic modifications function in another genetic background and increase the rate and yield of xylose-to-ethanol conversion in industrially relevant switchgrass hydrolysate, indicating that these specific genetic modifications may enable the sustainable production of industrial biofuels from yeast. We propose a model for how key regulatory mutations prime yeast for aerobic xylose fermentation by lowering the threshold for overflow metabolism, allowing mutations to increase xylose flux and to redirect it into fermentation products.