13C-metabolic flux analysis of ethanol-assimilating Saccharomyces cerevisiae for S-adenosyl-l-methionine production

Table 1 Fermentation profiles of the high-SAM-producing strain (Kyokai no. 6) under aerobic carbon-limited chemostat cultures (dilution rate of 0.06 h⁻¹)

	Carbon source
	Glucose^a	Ethanol
Carbon source consumption rate (mmol/g_CDW/h)	0.65	2.5
SAM content (mg/g_CDW)	0.58	1.8
Yield on carbon source
Cell (g_CDW/mol C)	15	12
CO₂ (mol C/mol C)^b	0.41	0.54
Specific production rate (μmol/g_CDW/h)
SAM	0.089	0.27
Malate	3.6	5.1
Acetate	4.9	29
Lactate	5.9	2.0
Pyruvate	0	0.27
Citrate	1.3	0.51
Succinate	4.2	4.3
Glycerol	0.35	0.44
Ethanol	0	–

All data were obtained from a single experiment. CDW cell dry weight
^aData from previous study [4]
^bEstimated by the carbon recoveries for biomass synthesis calculated from the specific growth rate and the reported elemental composition of carbon (glucose: 0.455 g/g_CDW, ethanol: 0.467 g/g_CDW) [15], and by the specific rates for carbon source consumption and for products including SAM productions. The total carbon recovery was considered to be 1.0

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