Engineered Saccharomyces cerevisiae capable of simultaneous cellobiose and xylose fermentation
Engineered Saccharomyces cerevisiae capable of simultaneous cellobiose and xylose fermentation
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DOI：
10.1073/pnas.1010456108
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发表时间：
2011-01-11
影响因子：
11.1
通讯作者：
Jin, Yong-Su
中科院分区：
文献类型：
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作者：
Ha, Suk-Jin;Galazka, Jonathan M.;Jin, Yong-Su
将植物生物质用于生物燃料生产将需要有效利用木质纤维素中的糖，主要是葡萄糖和木糖。然而，目前用于生物乙醇生产的酿酒酵母菌株发酵葡萄糖而不是木糖。酵母工程发酵木糖这样做很慢，不能利用木糖，直到葡萄糖被完全消耗。为了克服这些瓶颈，我们设计了酵母来共发酵木糖和纤维二糖的混合物。在这些酵母菌株中，纤维二糖的水解在通过高亲和力纤维糊精转运蛋白输入后通过细胞内β-葡糖苷酶的作用在酵母细胞内发生。纤维二糖的胞内水解使木糖发酵的葡萄糖抑制最小化，允许纤维二糖和木糖的共同消耗。所得的酵母菌株，共发酵纤维二糖和木糖的同时，并表现出改善的乙醇产率相比，无论是纤维二糖或木糖作为唯一的碳源发酵。我们还观察到改进的产率和生产率从共发酵实验进行模拟纤维素水解产物，这表明这是一个有前途的共发酵策略，纤维素生物燃料生产。在酵母中成功整合纤维二糖和木糖发酵途径是实现经济生物燃料生产的关键一步。
The use of plant biomass for biofuel production will require efficient utilization of the sugars in lignocellulose, primarily glucose and xylose. However, strains of Saccharomyces cerevisiae presently used in bioethanol production ferment glucose but not xylose. Yeasts engineered to ferment xylose do so slowly, and cannot utilize xylose until glucose is completely consumed. To overcome these bottlenecks, we engineered yeasts to coferment mixtures of xylose and cellobiose. In these yeast strains, hydrolysis of cellobiose takes place inside yeast cells through the action of an intracellular beta-glucosidase following import by a high-affinity cellodextrin transporter. Intracellular hydrolysis of cellobiose minimizes glucose repression of xylose fermentation allowing co-consumption of cellobiose and xylose. The resulting yeast strains, cofermented cellobiose and xylose simultaneously and exhibited improved ethanol yield when compared to fermentation with either cellobiose or xylose as sole carbon sources. We also observed improved yields and productivities from cofermentation experiments performed with simulated cellulosic hydrolyzates, suggesting this is a promising cofermentation strategy for cellulosic biofuel production. The successful integration of cellobiose and xylose fermentation pathways in yeast is a critical step towards enabling economic biofuel production.