Fig. 5.

Reverse labeling confirms that carbon in lactic and itaconic acid is incorporated from the captured CO₂. (A) Experimental design of the reverse labeling approach. After labeling the cells on ¹³C glycerol, we inoculated them into YNB and supplemented them with ^natC CO₂ (CO₂ with natural isotope distribution) and ¹³C MeOH. Samples were taken at different time points (day 3, day 5 and day 8) for the analysis with GC-TOFMS to monitor the change in the¹³C labeling pattern of the produced organic acids. (B) ¹³C labeling degree at different timepoints of the produced itaconic acid using the production strain on the left and the nongrower control. (C) ¹³C labeling degree at different timepoints of the produced lactic acid using the production strain on the left and the nongrower control. Error bars indicate the SD of 3 biological replicates. Detailed isotopologue distribution of the carbon atoms can be found in SI Appendix, Fig. S5.