The expression of a <i>Pichia stipitis</i> xylose reductase mutant with higher <i>K</i><sub>M</sub> for NADPH increases ethanol production from xylose in recombinant <i>Saccharomyces cerevisiae</i>
Bibliographic record
Abstract
Xylose fermentation by Saccharomyces cerevisiae requires the introduction of a xylose pathway, either similar to that found in the natural xylose-utilizing yeasts Pichia stipitis and Candida shehatae or similar to the bacterial pathway. The use of NAD(P)H-dependent XR and NAD(+)-dependent XDH from P. stipitis creates a cofactor imbalance resulting in xylitol formation. The effect of replacing the native P. stipitis XR with a mutated XR with increased K(M) for NADPH was investigated for xylose fermentation to ethanol by recombinant S. cerevisiae strains. Enhanced ethanol yields accompanied by decreased xylitol yields were obtained in strains carrying the mutated XR. Flux analysis showed that strains harboring the mutated XR utilized a larger fraction of NADH for xylose reduction. The overproduction of the mutated XR resulted in an ethanol yield of 0.40 g per gram of sugar and a xylose consumption rate of 0.16 g per gram of biomass per hour in chemostat culture (0.06/h) with 10 g/L glucose and 10 g/L xylose as carbon source.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".