AUTHOR=Mohammadi Nargesi Behrouz , Sprenger Georg A. , Youn Jung-Won 

TITLE=Metabolic Engineering of Escherichia coli for para-Amino-Phenylethanol and para-Amino-Phenylacetic Acid Biosynthesis

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=6

YEAR=2019

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2018.00201

DOI=10.3389/fbioe.2018.00201

ISSN=2296-4185

ABSTRACT=<p>Aromatic amines are an important class of chemicals which are used as building blocks for the synthesis of polymers and pharmaceuticals. In this study we establish a <italic>de novo</italic> pathway for the biosynthesis of the aromatic amines <italic>para-</italic>amino-phenylethanol (PAPE) and <italic>para-</italic>amino-phenylacetic acid (4-APA) in <italic>Escherichia coli</italic>. We combined a synthetic <italic>para</italic>-amino-<sc>l</sc>-phenylalanine pathway with the fungal Ehrlich pathway. Therefore, we overexpressed the heterologous genes encoding 4-amino-4-deoxychorismate synthase (<italic>pabAB</italic> from <italic>Corynebacterium glutamicum</italic>), 4-amino-4-deoxychorismate mutase and 4-amino-4-deoxyprephenate dehydrogenase (<italic>papB</italic> and <italic>papC</italic> from <italic>Streptomyces venezuelae</italic>) and ThDP-dependent keto-acid decarboxylase (<italic>aro</italic>10 from <italic>Saccharomyces cerevisiae</italic>) in <italic>E. coli</italic>. The resulting <italic>para</italic>-amino-phenylacetaldehyde either was reduced to PAPE or oxidized to 4-APA. The wild type strain <italic>E. coli</italic> LJ110 with a plasmid carrying these four genes produced (in shake flask cultures) 11 ± 1.5 mg l<sup>−1</sup> of PAPE from glucose (4.5 g l<sup>−1</sup>). By the additional cloning and expression of <italic>feaB</italic> (phenylacetaldehyde dehydrogenase from <italic>E. coli</italic>) 36 ± 5 mg l<sup>−1</sup> of 4-APA were obtained from 4.5 g l<sup>−1</sup> glucose. Competing reactions, such as the genes for aminotransferases (<italic>aspC</italic> and <italic>tyrB</italic>) or for biosynthesis of L-phenylalanine and L-tyrosine (<italic>pheA, tyrA</italic>) and for the regulator TyrR were removed. Additionally, the <italic>E. coli</italic> genes <italic>aroFBL</italic> were cloned and expressed from a second plasmid. The best producer strains of <italic>E. coli</italic> showed improved formation of PAPE and 4-APA, respectively. Plasmid-borne expression of an aldehyde reductase (<italic>yahK</italic> from <italic>E. coli</italic>) gave best values for PAPE production, whereas <italic>feaB</italic>-overexpression led to best values for 4-APA. In fed-batch cultivation, the best producer strains achieved 2.5 ± 0.15 g l<sup>−1</sup> of PAPE from glucose (11% C mol mol-1 glucose) and 3.4 ± 0.3 g l<sup>−1</sup> of 4-APA (17% C mol mol<sup>−1</sup> glucose), respectively which are the highest values for recombinant strains reported so far.</p>