Bio-Based Production of Uroporphyrin and Protoporphyrin-IX in Escherichia coli
Bibliographic record
Abstract
Porphyrins are tetrapyrrole compounds with diverse medical applications but challenging chemical and biological synthesis. This thesis reports a novel bioprocess approach for enhanced production of porphyrins including uroporphyrin (UP) and protoporphyrin IX (PP-IX) in Escherichia coli (E. coli) through the implementation of the C4/Shemin pathway. We first heterologously implemented the C4/Shemin pathway in an E. coli strain with an enlarged intracellular succinyl-CoA pool. Using plasmids with trc and gracmax promoters regulating the expression of synthesized gene operons, we characterized the effects of key pathway genes (hemA, hemB, hemC, hemD, hemE, and hemF, and hemG) on UP and PP-IX biosynthesis. By cultivating the resulting engineered E. coli strains in a glycerol-fed batch bioreactor under aerobic conditions, we produced up to 901.9 mg/L UP and 64.7 mg/L PP-IX. This thesis demonstrates the utility of synthetic biology and metabolic engineering strategies for large-scale bio-based production of UP and PP-IX.
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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) | 0.000 | 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) | 0.001 | 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".