Table 3.

Specific growth rate, stoichiometries of biomass and (by)product formation and biomass-specific acetate consumption rates in anaerobic bioreactor batch cultures of S. cerevisiae strains IME324 (reference strain), IMX2503 (Δgpd2 Δald6 pTDH3-eutE), and IMX2502 (non-ox PPP↑ Δgpd2 Δald6 pTDH3-eutE pDAN1-PRK 2x pTDH3-cbbM pTPI1-groES pTEF1-groEL).

Strain	IME324	IMX2503	IMX2502
Relevant genotype	Reference	gpd2∆ ald6∆ eutE	gpd2∆ ald6∆ eutE
			PRK 2x cbbM
µ (h−1)	0.31 ± 0.00	0.32 ± 0.00	0.25 ± 0.01
Y biomass/glucose (gx g−1)	0.071 ± 0.003	0.081 ± 0.001	0.072 ± 0.001
Y ethanol/glucose (mol mol −1)	1.65 ± 0.02	1.76 ± 0.01	1.71 ± 0.00
Y acetaldehyde/glucose (mol mol −1)	<0.005	<0.005	0.026 ± 0.001
Y glycerol/glucose (mol mol −1)	0.117 ± 0.000	0.033 ± 0.000	0.024 ± 0.002
Y acetate/glucose (mol mol−1)	−0.032 ± 0.004	−0.084 ± 0.002	−0.023 ± 0.001
Glycerol production (mmol gx−1)	8.5 ± 0.1	2.1 ± 0.1	1.8 ± 0.1
Acetate consumption (mmol gx−1)	2.3 ± 0.3	5.7 ± 0.3	1.7 ± 0.1
q acetate (mmol gx−1 h−1)	−0.7 ± 0.0	−1.8 ± 0.1	−0.4 ± 0.0
Electron recoveries (%)	99–101	99–100	100–101

Cultures were grown on synthetic medium with 20 g L⁻¹ of glucose and 50 mmol L⁻¹ of acetate at pH 5 and at 30°C and sparged with a 90:10 mixture of N₂ and CO₂. Stoichiometries of biomass and metabolite production formation were calculated from at least six sampling points in the exponential growth phase. Values represent averages ± mean deviations of measurements on independent duplicate cultures. Since the high concentration of CO₂ in the inlet gas precluded construction of carbon balances, degree-of-reduction balances were used to verify data consistency (Roels 1980). Non-ox PPP↑ indicates the integration of the expression cassettes of pTDH3-RPE1, pPGK1-TKL1, pTEF1-TAL1, pPGI1-NQM1, pTPI1-RKI1, and pPYK1-TKL2. Symbols: μ, specific growth rate; g_x, gram biomass; Y, yield; q_acetate: biomass-specific rate of acetate consumption in exponential growth phase.