Many phenylalanine- and tyrosine-producing strains have used plasmid-based overexpression of pathway genes. The resulting strains achieved high titers and yields of phenylalanine and tyrosine. Chromosomally engineered, plasmid-free producers have shown lower titers and yields than plasmid-based strains, but the former are advantageous in terms of cultivation cost and public health/environmental risk. Therefore, we engineered here the Escherichia coli chromosome to create superior phenylalanine- and tyrosine-overproducing strains that did not depend on plasmid-based expression. Integration into the E. coli chromosome of two central metabolic pathway genes (ppsA and tktA) and eight shikimate pathway genes (aroA, aroB, aroC, aroD, aroE, aroG^fbr, aroL, and pheA^fbr), controlled by the T7lac promoter, resulted in excellent titers and yields of phenylalanine; the superscript “fbr” indicates that the enzyme encoded by the gene was feedback resistant. The generated strain could be changed to be a superior tyrosine-producing strain by replacing pheA^fbr with tyrA^fbr. A rational approach revealed that integration of seven genes (ppsA, tktA, aroA, aroB, aroC, aroG^fbr, and pheA^fbr) was necessary as the minimum gene set for high-yield phenylalanine production in E. coli MG1655 (tyrR, adhE, ldhA, pykF, pflDC, and ascF deletant). The phenylalanine- and tyrosine-producing strains were further applied to generate phenyllactic acid-, 4-hydroxyphenyllactic acid-, tyramine-, and tyrosol-producing strains; yield of these aromatic compounds increased proportionally to the increase in phenylalanine and tyrosine yields.

中文翻译：

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染色体工程产生无质粒的苯丙氨酸和酪氨酸过量生产的大肠杆菌菌株，可用于产生芳香化合物的细菌的产生。

许多产生苯丙氨酸和酪氨酸的菌株已使用基于质粒的通路基因过表达。所得菌株实现了高滴度和苯丙氨酸和酪氨酸的产率。经染色体工程改造的无质粒生产者的滴度和产量均低于基于质粒的菌株，但前者在培养成本和公共卫生/环境风险方面具有优势。因此，我们在这里设计了大肠杆菌染色体，以产生不依赖于质粒表达的优良的苯丙氨酸和酪氨酸过量生产菌株。两个中央代谢途径基因（ppsA和tktA）和八个shikimate途径基因（aroA）整合到大肠杆菌染色体中。，aroB，AROC，AROD，净资产回报率，aroG ^FBR，卡罗尔，和的pheA ^FBR），由T7lac启动子控制的，导致了优良的效价和苯丙氨酸的产率; 上标“ fbr ”表示该基因编码的酶具有反馈抗性。通过用tyrA ^fbr代替pheA ^fbr，可以将产生的菌株改变为优良的酪氨酸生产菌株。合理的方法揭示了七个基因（ppsA，tktA，aroA，aroB）的整合。，aroC，aroG ^fbr和pheA ^fbr是必需的，是在大肠杆菌MG1655中高产苯丙氨酸生产的最小基因集（tyrR，adhE，ldhA，pykF，pflDC和ascF缺失）。进一步将产生苯丙氨酸和酪氨酸的菌株用于产生苯乳酸，4-羟基苯基乳酸，酪胺和酪醇的菌株。这些芳族化合物的产率与苯丙氨酸和酪氨酸产率的增加成比例地增加。