Fig. 2

Overexpression of a feedback-resistant phenylalanine biosynthetic pathway. The two feedback-resistant alleles of KmARO4 and KmARO7 constructed based on homology to S. cerevisiae are functional, with their episomal overexpression leading to the production of Ehrlich alcohols of phenylalanine (white) and tyrosine (grey) from the overflow of their increased synthesis, as well as excess shikimate (dark grey). All compounds were measured by HPLC in culture medium after 48 h growth at 30 °C as described in the Methods. Subsequent co-expression of the shikimate (KmARO4^fbr, KmARO1, KmARO2) + KmARO7^fbr and phenylalanine (KmARO4^fbr + KmARO1 + KmARO2 + KmARO7^fbr + KmPHA2 + KmARO9) pathways increased their production and converted more shikimate to amino acids. Chromosomal integration of the pathway further improved phenylalanine and tyrosine production. Strains marked with an asterisk (*) show a significantly higher level of 2-PE relative to that produced by ASR.004 as determined by an independent t-test (p < 0.05). The data in the bar plots are the mean ± s.d. of at least three biological replicates. All data plotted in this and following graphs can be found in Additional file 2: Supplementary Data 1