酿酒酵母转化木糖生产化学品的研究进展

Progress in studies on production of chemicals from xylose by Saccharomyces cerevisiae

摘要:

木糖的有效利用是木质纤维素生产生物燃料或化学品经济性转化的基础。30年来，通过理性代谢改造和适应性进化等工程策略，显著提高了传统乙醇发酵微生物——酿酒酵母Saccharomyces cerevisiae的木糖代谢能力。因此，近年来在酿酒酵母中利用木糖生产化学品的研究逐步展开。研究发现，酿酒酵母分别以木糖和葡萄糖为碳源时，其转录组和代谢组存在明显差异。与葡萄糖相比，木糖代谢过程中细胞整体呈现出Crabtree-negative代谢特征，如有限的糖酵解途径活性减少了丙酮酸到乙醇的代谢通量,以及增强的胞质乙酰辅酶A合成和呼吸能量代谢等，这都有利于以丙酮酸或乙酰辅酶A为前体的下游产物的有效合成。文中对酿酒酵母木糖代谢途径改造与优化、木糖代谢特征以及以木糖为碳源合成化学品的细胞工厂构建等方面进行了详细综述，并对木糖作为重要碳源在大宗化学品生物合成中存在的困难和挑战以及未来研究方向进行了总结与展望。

Abstract:

Effective utilization of xylose is a basis for economic production of biofuels or chemicals from lignocellulose biomass. Over the past 30 years, through metabolic engineering, evolutionary engineering and other strategies, the metabolic capacity of xylose of the traditional ethanol-producing microorganism Saccharomyces cerevisiae has been significantly improved. In recent years, the reported results showed that the transcriptome and metabolome profiles between xylose and glucose metabolism existed significant difference in recombinant yeast strains. Compared with glucose, the overall process of xylose metabolism exhibits Crabtree-negative characteristics, including the limited glycolytic pathway activity, which reduces the metabolic flux of pyruvate to ethanol, and the enhanced cytosolic acetyl-CoA synthesis and respiratory energy metabolism. These traits are helpful to achieve efficient synthesis of downstream products using pyruvate or acetyl-CoA as precursors. This review provides a detailed overview on the modification and optimization of xylose metabolic pathways in S. cerevisiae, the characteristics of xylose metabolism, and the construction of cell factories for production of chemicals using xylose as a carbon source. Meanwhile, the existed difficulties and challenges, and future studies on biosynthesis of bulk chemicals using xylose as an important carbon source are proposed.