Optimizing anaerobic growth rate and fermentation kinetics in Saccharomyces cerevisiae strains expressing Calvin-cycle enzymes for improved ethanol yield

Table 5 Specific growth rates (μ), yields (Y) of biomass, ethanol and glycerol on glucose and stoichiometric relationships between glycerol production and biomass formation in anaerobic bioreactor batch cultures of S. cerevisiae strains IME369 and IMX1489

Strain	IME369	IMX1489
Relevant genotype	GPD1 GPD2	GPD1 gpd2Δ pDAN1-prk cbbm non-ox PPP↑
μ (h⁻¹)	0.31 ± 0.00	0.30 ± 0.01
Y biomass/glucose (g g⁻¹)	0.091 ± 0.009	0.096 ± 0.001*
Y ethanol/glucose (g g⁻¹)	0.376 ± 0.005	0.421 ± 0.002*
Y glycerol/glucose (g g⁻¹)	0.107 ± 0.004	0.014 ± 0.000**
Glycerol produced/biomass [mmol (g biomass)⁻¹]	12.189 ± 1.080	1.669 ± 0.082**

Cultures were grown on synthetic medium containing 20 g L⁻¹ glucose (pH 5). Specific growth rates and stoichiometries were calculated from sample points during the mid-exponential growth phase. Values represent averages ± mean deviations of measurements on independent duplicate cultures. * (p < 0.02) and ** (p < 0.01) denote statistical significance of differences between IME324 (Table 3) and strains IME369 and IMX1489 in Student’s t tests. Degree of reduction balances constructed over the exponential growth phase yielded electron recoveries between 96 and 100%

ISSN: 1754-6834