Fig. 5
From: Rewiring carbon metabolism in yeast for high level production of aromatic chemicals
Optimization of carbon distribution increases p-HCA production. a Schematic illustration of carbon redistribution between glycolysis and the AAA biosynthesis pathway through a promoter library screening approach. A promoter library was created to replace the original promoters of PFK1, PFK2, and PYK1, which encode phosphofructokinase and pyruvate kinase, respectively, at key nodes between glycolysis and the AAA biosynthesis pathway. This promoter library was transformed into a yeast strain harboring the PHK pathway alongside the upregulated shikimate pathway, with the resulting strain screened by using a l-Tyr-derived pathway that indicated increased tyrosine production via the formation of the yellow pigment betaxanthin. Selected promoters exhibiting enhanced color intensity are listed in Supplementary Table 2. Furthermore, AAA degradation pathway was eliminated by deleting the corresponding genes (marked with a red cross) in the final strains. Open triangles indicate the use of constitutive strong promoters for controlling gene expression, while filled triangles indicate the use of galactose-inducible promoters. b Simultaneous optimization of the promoters of PFK1, PFK2, and PYK1 improves p-HCA production. c Removing the AAA degradation pathway further enhances p-HCA titers. Deletion of GAL80 was additionally introduced to enable the induction of GAL promoters without the addition of galactose. For shake-flask cultivation, cells were grown in defined minimal medium with six tablets of FeedBeads as the sole carbon source and 1% galactose as the inducer when required. For strains with the deletion of GAL80, no galactose was supplemented. Cultures were sampled after 96 h of growth for p-HCA detection. Statistical analysis was performed by using Student’s t test (one-tailed; two-sample unequal variance; *p < 0.05, **p < 0.01, ***p < 0.001). All data represent the mean of n = 3 biologically independent samples and error bars show standard deviation. The source data underlying figures b and c are provided in a Source Data file
