Fig. 4.

(two columns) Engineering methylxanthine production using an alternate pathway. The top molecular structure illustrates methyltransferases used in the study and their corresponding N-methylation position on the xanthine backbone. The plot below represents the titer of four different methylxanthines produced in the media of the engineered strains, optimized for 1-, 3-methylxanthine and theophylline production (grey) and for 3-methylxanthine production (light blue). Production of methylxanthines was analyzed by LC–MS/MS and data are reported as the mean and standard deviation of biological triplicates. Relevant genetic contents for each strain are displayed next to the vertical bar on the left of the plot (see Table 1 for complete strain information).