Metabolic engineering strategies for optimizing acetate reduction, ethanol yield and osmotolerance in Saccharomyces cerevisiae

Table 3 Specific growth rates (μ) and stoichiometric relationships between glycerol production and biomass formation, acetate consumption and glucose consumption, and acetate consumption and biomass formation in anaerobic bioreactor batch cultures of S. cerevisiae strains with different genetic modifications in glycerol and acetate metabolism

Strain	IME324	IMX992	IMX884	IMX776	IMX901	IMX888^a
Relevant genotype	GPD1 GPD2	GPD1 GPD2 sga1::eutE	GPD1 gpd2::eutE	gpd1::gpsA gpd2::eutE	gpd1::gpsA gpd2::eutE ald6Δ	gpd1Δ gpd2::eutE
μ (h⁻¹)	0.31 ± 0.01	0.30 ± 0.00	0.31 ± 0.01	0.24 ± 0.01	0.24 ± 0.01	0.26 ± 0.01
Ratio glycerol produced/biomass [mmol (g biomass)⁻¹]	9.19 ± 0.08	8.28 ± 0.14	1.92 ± 0.06	<0.1	<0.1	<0.1
Ratio acetate consumed/biomass [mmol (g biomass)⁻¹]	2.43 ± 0.16	3.35 ± 0.08	5.77 ± 0.25	6.66 ± 0.01	6.41 ± 0.28	6.92 ± 0.12
Ratio acetate consumed/glucose (g g⁻¹)	0.010 ± 0.000	0.015 ± 0.000	0.026 ± 0.001	0.031 ± 0.001	0.031 ± 0.000	0.032 ± 0.000

Cultures were grown on synthetic medium containing 20 g L⁻¹ glucose and 3 g L⁻¹ acetic acid (pH 5). Specific growth rates and stoichiometries were calculated from the mid-exponential growth phase and represent averages ± mean deviations of data obtained from independent duplicate cultures. In all cultures, carbon recoveries were between 95 and 100%. Enzyme activities of acetylating-acetaldehyde dehydrogenase in cell extracts of eutE-expressing strains were similar (Additional file 2)
^aData on strain IMX888 were taken from [29]

ISSN: 2731-3654