TABLE 1.

Percentage of ¹³C labeling on the fermentation products derived from the metabolism of [¹³C]glucose by cell suspensions of T. zilligii grown on tryptone^a

Substrate	Value for product:
	Acetate			Formate
	Total amt (μmol/mg of protein)	13CH3COO− (%)	CH313COO− (%)	Total amt (μmol/mg of protein)	H13COO− (%)
[1-13C]glucoseb	0.94 ± 0.26	9 ± 1	—e	0.19 ± 0.06	78 ± 3
[2-13C]glucosec	0.93 ± 0.07	13 ± 2	6 ± 2	0.17 ± 0.04	—
[3-13C]glucosec	1.05 ± 0.10	—	18 ± 2	0.21 ± 0.04	—
[4-13C]glucosec	1.03 ± 0.07	—	2 ± 1	0.18 ± 0.03	1 ± 1
[5-13C]glucosec	1.01 ± 0.06	1 ± 1	12 ± 2	0.13 ± 0.03	—
[6-13C]glucosed	1.19	27	—	0.21	4

^aCell suspensions were incubated with 15 mM glucose at 75°C for 2 h. Fermentation products were quantified in supernatants by proton NMR using formate as a concentration standard. Percentages of ¹³C labeling were calculated from the areas of the respective resonances in the ¹H spectra. Isotopic enrichment on the carboxylic group of acetate was confirmed by comparing the intensity of the carboxylic resonance in the ¹³C spectra with that of the resonance of the methyl group and taking into account the enrichment of this group determined by ¹H NMR. The natural abundance of ¹³C (1.1%) was subtracted, and therefore the values represent the excess of ¹³C in the metabolites. 

^bAverage values for five independent experiments. 

^cAverage values for two independent experiments. 

^dResult from a single experiment. 

^e—, not detected.