Genetic Engineering of an Industrial Strain of Saccharomyces cerevisiae for L-Malic Acid Degradation via an Efficient Malo-Ethanolic Pathway
Bibliographic record
Abstract
The optimal ratio of L-malic and L-tartaric acid in relation to other wine components is one of the most important aspects that ultimately determine wine quality during winemaking. Winemakers routinely rely on the judicious use of malolactic fermentation (MLF) after alcoholic fermentation to deacidify and stabilise their wines. However, due to theunreliability of the process and unsuitable sensory modifications in some grape cultivars, especially for fruity-floral wines, MLF is often regarded as problematic and undesirable. Alternative methods for reducing the amounts of L-malic acid in wine will contribute to improving the production of quality wines in the future, especially in coolclimate regions. Most wine yeast strains of Saccharomyces are unable to effectively degrade L-malic acid, whereas the fission yeast Schizosaccharomyces pombe efficiently degrades high concentrations of L-malic acid by means of malo-ethanolic fermentation. However, strains of S. pombe are not suitable for vinification due to the production of undesirable off-flavours. Previously, the 5. pombe malate permease (mael) and malic enzyme (mae2) genes were successfully expressed under the 3-phosphoglycerate kinase (PGK1) regulatory elements in 5. cerevisiae, resulting in a recombinant laboratory strain of S. cerevisiae with an efficient malo-ethanolic pathway. Stable integration of the S. pombe malo-ethanolic pathway genes has now been obtained through the construction of a unique integration strategy in a commercial wine yeast strain. Co-transformation of the linear integration cassette containing the mael and mae2 genes and PGK1 regulatory elements and a multi-copy plasmid containing the phleomycin-resistance marker into a commercial Saccharomyces cerevisiae strain resulted in the successful transformation and integration of the malo-ethanolic genes. The recombinant 5. cerevisiae strain was successfully cured of phleomycin-resistance plasmid DNA in order to obtain malo-ethanolic yeast containing only yeast-derived DNA. The integrated malo-ethanolic genes were stable in 5. cerevisiae and during synthetic and grape must fermentation, L-malic acid was completely fermented to ethanol without any negative effect on fermentation kinetics and wine quality.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".