Salicin is a natural glycoside compound widely used to treat fever, inflammation, and analgesia. Currently, salicin is primarily extracted from willow bark, which is not only cumbersome in terms of extraction and separate steps, but also subject to seasonal and geographic limitations. In this study, a highly efficient biosynthetic pathway for salicin synthesis was designed and constructed in E. coli. The most important precursor in the synthetic pathway of salicin designed in this study is salicyl alcohol. Building on a previously constructed biosynthetic salicylic acid metabolic pathway, the production of salicyl alcohol in shake flask fermentation reached 1.7 g/L by increasing the supply of shikimic acid pathway precursor PEP and salicyl alcohol precursor chorismate. According to the principle of substrate similarity, this study identified the key enzyme OsSGT1 from Oryza sativa, which uses E. coli endogenous UDP-glucose as a glycosyl donor to glycosylate salicyl alcohol into salicin. By redefining the optimal substrate of OsSGT1, and balancing metabolic flux along with increasing the supply of UDP-glucose, salicin production in shake flasks reached 4 g/L. Finally, culturing the high-yield strain in a 3-L fermenter resulted in the synthesis of 14.62 g/L of salicin. To the best of our knowledge, this achievement marks the highest salicin production through microbial fermentation to date.

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设计一种在大肠杆菌中高效生物合成水杨苷的新途径


水杨苷是一种天然糖苷化合物，广泛用于治疗发烧、炎症和镇痛。目前，水杨苷主要从柳树皮中提取，不仅提取和单独步骤繁琐，而且受季节和地理限制。本研究设计并构建了一种在大肠杆菌中合成水杨苷的高效生物合成途径。本研究设计的水杨苷合成途径中最重要的前体是水杨醇。在先前构建的生物合成水杨酸代谢途径的基础上，通过增加莽草酸途径前体 PEP 和水杨醇前体绒毛酸酯的供应，摇瓶发酵中水杨醇的产量达到 1.7 g/L。根据底物相似性原理，本研究从水稻中鉴定出关键酶 OsSGT1，它利用大肠杆菌内源性 UDP-葡萄糖作为糖基供体，将水杨醇糖化成水杨苷。通过重新定义 OsSGT1 的最佳底物，平衡代谢通量并增加 UDP-葡萄糖的供应，摇瓶中的水杨苷产量达到 4 g/L。最后，在 3 L 发酵罐中培养高产菌株，合成了 14.62 g/L 的水杨苷。据我们所知，这一成就标志着迄今为止通过微生物发酵产生的水杨苷达到最高水平。