Fig. 3.

Isotopic profiling of anoxic-electrogenic P. putida KT2440 grown on [¹³C₆] glucose. The data display the ¹³C enrichment of extracellular accumulated organic acids (A) and intracellular amino acids (B), sampled after 100 h from the bio-electrochemical process using [¹³C₆] glucose as the substrate. For comparison, the BES process was conducted using naturally labelled glucose, i.e. non-¹³C-labelled glucose, as the substrate. The bar graphs represent the measured mass isotopomer distributions of the analytes (m + 0 to m + x) using [¹³C₆] glucose (lower bars, lab.) and non-¹³C-labelled glucose (upper bars, unlab.). The numbers given above the bar charts display the summed fraction labelling from the tracer study on [¹³C₆] glucose, calculated after correction of the measured labelling data for natural isotope abundance. As shown, gluconate and 2-ketogluconate exclusively originate from glucose, while the other organic acids partially stem from the [¹³C₆]-labelled glucose and (non-labelled) biomass constituents. Amino acids are largely derived from biomass