Fig. 4

Optimising phenylalanine production by increasing precursor supply to the phenylalanine pathway. a Overexpressing heterologous enzymes to increase precursor supply either by themselves or with native enzymes had more variable results, with strategies that worked in KmASR.004 not working in KmASR.046. Ultimately precursor supply via the PPP (KmASR.062) could be matched by using a phosphoketolase (Xfpk) from B. breve and a phosphotransacetylase (Pta) from S. enterica (KmASR.149). b Using a partial (KmASR.062) or full (KmASR.047) overexpression of the non-oxidative pentose phosphate pathway (PPP), we were able to increase phenylalanine production in strain KmASR.046 overexpressing a feedback-resistant phenylalanine pathway by 33%. Strains producing significantly higher amounts of 2-PE relative to that produced by KmASR.046 as determined by an independent t-test are marked by an asterisk (*p < 0.05) or a hash (^#p < 0.005) All data are plotted as the mean ± s.d. of at least three biological replicates. Km: Kluyveromyces marxianus, Ct: Chaetomium thermophilum, Tt: Thielavia terrestris, Bb: Bifidobacter breve, Se: Salmonella enterica