Production Of Tyrosine And Dervate Through Phenylalanine Hydroxylation In Escherichia Coli

Tyrosine is a proteinogenic aromatic amino acid that is often used as a supplement of food and animal feed, as well as a (bio-)synthetic precursor to various pharmaceutically or industrially important molecules. Extensive metabolic engineering efforts have been made towards the efficient and cost-effective microbial production of tyrosine. Conventional strategies usually focus on eliminating intrinsic feedback inhibition and redirecting carbon flux into the shikimate pathway. In this study, we found that continuous conversion of phenylalanine into tyrosine by the action of tetrahydromonapterin (MH4)-utilizing phenylalanine 4-hydroxylase (P4H) can bypass the feedback inhibition in Escherichia coli, leading to tyrosine accumulation in the cultures. Specific research contents include:1、Expressed plasmid pZE-XcABM in the wild type strains of E. coli, get a L-tyrosine production of 262 mg·L-1 yield, verified the feasibility of research strategy.2、Build the plasmid pCS-AX and plasmid pCS-APTA-AX, and then expressed in the strains previously built. After the optimization of fermentation condition, on the basis of the original, L-tyrosine product can improve the yield to 401 mg·L-1.3、Furthermore, the plasmid pSA-hpaBC was built and expressed in Escherichia coli genetic engineering strain, to detect the possibility of production of L-DOPA.This work demonstrated a novel approach to tyrosine production and verified the possibility to alleviate feedback inhibition by creating a phenylalanine sink. Furthermore, we tried to produce of L-tyrosine derivative L-DOPA, but as a result of oxidation problem. We did not get the desired production. Although for tyrosine derivatives research was not successful, but for thOPA microbial production, separated from the product in a timely and antioxidant aspects should be considered.