Vanillin is one of the world’s most extensively used flavoring agents with high application value. However, the yield of vanillin biosynthesis remains limited due to the low efficiency of substrate uptake and the inhibitory effect on cell growth caused by vanillin. Here, we screened high-efficiency ferulic acid importer TodX and vanillin exporters PP_0178 and PP_0179 by overexpressing genes encoding candidate transporters in a vanillin-producing engineered Escherichia coli strain VA and further constructed an autoregulatory bidirectional transport system by coexpressing TodX and PP_0178/PP_0179 with a vanillin self-inducible promoter ADH7. Compared with strain VA, strain VA-TodX-PP_0179 can efficiently transport ferulic acid across the cell membrane and convert it to vanillin, which significantly increases the substrate utilization rate efficiency (14.86%) and vanillin titer (51.07%). This study demonstrated that the autoregulatory bidirectional transport system significantly enhances the substrate uptake efficiency while alleviating the vanillin toxicity issue, providing a promising viable route for vanillin biosynthesis.

中文翻译：

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在香草醛生产大肠杆菌细胞工厂中构建新型香草醛诱导的自动调节双向运输系统


香兰素是世界上应用最广泛的调味剂之一，具有很高的应用价值。然而，由于底物摄取效率低以及香草醛对细胞生长的抑制作用，香草醛生物合成的产量仍然有限。在这里，我们通过在产香草醛工程大肠杆菌VA中过表达编码候选转运蛋白的基因来筛选高效阿魏酸输入蛋白TodX和香草醛输出蛋白PP_0178和PP_0179，并通过将TodX和PP_0178/PP_0179与香草醛自诱导启动子 ADH7。与菌株VA相比，菌株VA-TodX-PP_0179能够高效地将阿魏酸跨细胞膜转运并转化为香草醛，显着提高了底物利用率（14.86%）和香草醛效价（51.07%）。这项研究表明，自动调节双向运输系统显着提高了底物吸收效率，同时减轻了香草醛毒性问题，为香草醛生物合成提供了一条有前途的可行途径。