| Content Provider | Springer Nature : BioMed Central |
|---|---|
| Author | Pagliardini, Julien Hubmann, Georg Bideaux, Carine Alfenore, Sandrine Nevoigt, Elke Guillouet, Stéphane E |
| Abstract | Background Glycerol is the major by-product accounting for up to 5% of the carbon in Saccharomyces cerevisiae ethanolic fermentation. Decreasing glycerol formation may redirect part of the carbon toward ethanol production. However, abolishment of glycerol formation strongly affects yeast's robustness towards different types of stress occurring in an industrial process. In order to assess whether glycerol production can be reduced to a certain extent without jeopardising growth and stress tolerance, the yeast's capacity to synthesize glycerol was adjusted by fine-tuning the activity of the rate-controlling enzyme glycerol 3-phosphate dehydrogenase (GPDH). Two engineered strains whose specific GPDH activity was significantly reduced by two different degrees were comprehensively characterized in a previously developed Very High Ethanol Performance (VHEP) fed-batch process. Results The prototrophic strain CEN.PK113-7D was chosen for decreasing glycerol formation capacity. The fine-tuned reduction of specific GPDH activity was achieved by replacing the native GPD1 promoter in the yeast genome by previously generated well-characterized TEF promoter mutant versions in a gpd2 Δ background. Two TEF promoter mutant versions were selected for this study, resulting in a residual GPDH activity of 55 and 6%, respectively. The corresponding strains were referred to here as TEFmut7 and TEFmut2. The genetic modifications were accompanied to a strong reduction in glycerol yield on glucose; the level of reduction compared to the wild-type was 61% in TEFmut7 and 88% in TEFmut2. The overall ethanol production yield on glucose was improved from 0.43 g g-1 in the wild type to 0.44 g g-1 measured in TEFmut7 and 0.45 g g-1 in TEFmut2. Although maximal growth rate in the engineered strains was reduced by 20 and 30%, for TEFmut7 and TEFmut2 respectively, strains' ethanol stress robustness was hardly affected; i.e. values for final ethanol concentration (117 ± 4 g L-1), growth-inhibiting ethanol concentration (87 ± 3 g L-1) and volumetric ethanol productivity (2.1 ± 0.15 g l-1 h-1) measured in wild-type remained virtually unchanged in the engineered strains. Conclusions This work demonstrates the power of fine-tuned pathway engineering, particularly when a compromise has to be found between high product yield on one hand and acceptable growth, productivity and stress resistance on the other hand. Under the conditions used in this study (VHEP fed-batch), the two strains with \"fine-tuned\" GPD1 expression in a gpd2 Δ background showed slightly better ethanol yield improvement than previously achieved with the single deletion strains gpd1 Δ or gpd2 Δ. Although glycerol reduction is known to be even higher in a gpd1 Δ gpd2 Δ double deletion strain, our strains could much better cope with process stress as reflected by better growth and viability. |
| Related Links | https://microbialcellfactories.biomedcentral.com/counter/pdf/10.1186/1475-2859-9-36.pdf |
| Ending Page | 13 |
| Page Count | 13 |
| Starting Page | 1 |
| File Format | HTM / HTML |
| ISSN | 14752859 |
| DOI | 10.1186/1475-2859-9-36 |
| Journal | Microbial Cell Factories |
| Issue Number | 1 |
| Volume Number | 9 |
| Language | English |
| Publisher | BioMed Central |
| Publisher Date | 2010-05-21 |
| Access Restriction | Open |
| Subject Keyword | Applied Microbiology Biotechnology Microbiology Microbial Genetics and Genomics Enzymology Genetic Engineering Ethanol Production Ethanol Yield Ethanol Tolerance Glycerol Production GPDH Activity |
| Content Type | Text |
| Resource Type | Article |
| Subject | Applied Microbiology and Biotechnology Bioengineering Biotechnology |
| Journal Impact Factor | 4.3/2023 |
| 5-Year Journal Impact Factor | 5.5/2023 |
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