Table 1.
Reported impacts on glycerol production, maximum specific growth rate and ethanol production in anaerobic batch cultures of S. cerevisiae strains subjected to different pathway engineering strategies aimed at reducing glycerol production and improving ethanol yield. Depending on the studies, changes in product yields were either expressed per amount of substrate or per amount of biomass. Subscript x denotes dry biomass, ↑ indicates overexpression of native S. cerevisiae genes.
| Strategy | Genotype | Glycerol yield | Growth rate | Ethanol yield | Reference |
|---|---|---|---|---|---|
| Altered cofactor specificity of ammonium assimilation | gdh1Δ GLN1↑GLT1↑ | −38% (g/g glucose) | −10% | +10% (g/g glucose) | [18] |
| gdh1Δ GDH2↑ | −30% (g/g glucose) | −5% | +3% (g/g glucose) | [18] | |
| NADH-dependent reduction of acetate to ethanol | gpd1Δ gpd2Δ Ec-mphF | −100% (g/gx) | −56% | +13% (g/g glucose) | [90] |
| (Ec = E. coli) | gpd1Δ gpd2Δ Ec-eutE | −100% (g/gx) | −7% | +9% (g/g glucose) | [94] |
| NADH-dependent reduction of acetate to ethanol with increased NADH generation via pentose-phosphate pathway | gnd2Δ gnd1Δ gndAΔ ald6Δ gpd1Δ gpd2Δ Ec-eutE | −100% (g/gx) | −29% | +11% (g/g glucose) | [94] |
| NADH re-oxidation via expression of Calvin-cycle enzymes, optimized for anaerobic growth rate (So = Spinacia oleracea, Td = Thiobacillus denitrificans) | gpd2Δ RPE1↑TKL1↑ TAL1↑ NQM1↑ RKI1↑ TKL2↑ So-prk Td-cbbm (9 copies) Ec-groES, Ec-groEL | −86% (g/gx) | 0% | +15% (g/g glucose) | [77] |
| Reduced NADH and ATP formation in glycolysis by expression of gapN | Sm-gapN | −40% (g/g glucose) | 0% | +2% (g/g glucose) | [64] |
| (Sm = Streptococcus mutans) | gpd1Δ Sm-gapN TPS1↑ TPS2↑ | −73% (g/g glucose) | 0% | +8% (g/g glucose) | [62] |