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Lütke-Eversloh, T and Stephanopoulos, G (2007) L-tyrosine production by deregulated strains of Escherichia coli. Appl. Microbiol. Biotechnol. 75:103-10


The excretion of the aromatic amino acid L: -tyrosine was achieved by manipulating three gene targets in the wild-type Escherichia coli K12: The feedback-inhibition-resistant (fbr) derivatives of aroG and tyrA were expressed on a low-copy-number vector, and the TyrR-mediated regulation of the aromatic amino acid biosynthesis was eliminated by deleting the tyrR gene. The generation of this L: -tyrosine producer, strain T1, was based only on the deregulation of the aromatic amino acid biosynthesis pathway, but no structural genes in the genome were affected. A second tyrosine over-producing strain, E. coli T2, was generated considering the possible limitation of precursor substrates. To enhance the availability of the two precursor substrates phosphoenolpyruvate and erythrose-4-phosphate, the ppsA and the tktA genes were over-expressed in the strain T1 background, increasing L: -tyrosine production by 80% in 50-ml batch cultures. Fed-batch fermentations revealed that L: -tyrosine production was tightly correlated with cell growth, exhibiting the maximum productivity at the end of the exponential growth phase. The final L: -tyrosine concentrations were 3.8 g/l for E. coli T1 and 9.7 g/l for E. coli T2 with a yield of L: -tyrosine per glucose of 0.037 g/g (T1) and 0.102 g/g (T2), respectively.


PubMed Online version:10.1007/s00253-006-0792-9


Biotechnology/methods; Culture Media; Escherichia coli/genetics; Escherichia coli/growth & development; Escherichia coli/metabolism; Escherichia coli K12/genetics; Escherichia coli K12/growth & development; Escherichia coli K12/metabolism; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Fermentation; Gene Expression Regulation, Bacterial; Genetic Engineering/methods; Tyrosine/biosynthesis


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