Systems engineering of <i>Escherichia coli</i> for high-level hydroxytyrosol production.
Engineered E. coli achieved the highest hydroxytyrosol production to date, offering a potential platform for scalable biomanufacturing.
Where it sits
this study against the rest of the cerebrolysin corpusSummary and findings
This study engineered an Escherichia coli strain to produce hydroxytyrosol (HT) from glucose, achieving a titer of 9.25 g/L. The approach involved metabolic pathway optimization and cofactor engineering to enhance production and tolerance. The findings suggest a promising biomanufacturing platform for HT production.
Abstract
Hydroxytyrosol (HT) is a potent polyphenolic antioxidant widely utilized in the biomedical and food industries. However, its high-level microbial biosynthesis is primarily hindered by the metabolic flux imbalances and severe cellular toxicity. In this study, an artificial synthetic pathway from 4-hydroxyphenylpyruvate was constructed in an engineered l-phenylalanine producing <i>E</i>. <i>coli</i> chassis. Building on this, the endogenous precursor supply was strengthened via targeted promoter engineering of <i>aroK</i>, <i>aroC</i>, and <i>tyrA</i>, and the heterologous HT biosynthetic pathway was enhanced by overexpressing ARO10. To mitigate intermediate l-DOPA accumulation, co-expression of l-DOPA decarboxylase (DODC) and tyramine oxidase (TYO) reduced l-DOPA by 63.7%, while expression of l-amino acid deaminase (LAAD) reduced l-DOPA by 76.1%. Additionally, precise cofactor engineering was implemented; overexpressing the riboflavin metabolic genes <i>ribH</i>, <i>ribC</i>, and <i>ribF</i>, alongside introducing <i>pntAB</i>, increased HT production by 30.9% and 12.7%, respectively. Furthermore, transcriptomic analysis under HT stress revealed significant upregulation of genes related to transport and stress responses. Among these targets, overexpressing <i>marR</i> substantially improved cellular tolerance and HT production. Finally, during a 5-L bioreactor fermentation supplemented with Fe<sup>2+</sup> and ascorbic acid, the engineered strain achieved an HT titer of 9.25 g/L, a yield of 0.102 g/g glucose, and a productivity of 0.193 g/L/h. This study reports the highest HT titer to date in <i>E. coli</i> using glucose as the carbon source, providing a robust biomanufacturing platform.
Background
Hydroxytyrosol (HT) is a valuable antioxidant with applications in the biomedical and food industries. Current microbial biosynthesis methods face challenges due to metabolic imbalances and cellular toxicity. This study aims to overcome these barriers by engineering E. coli for efficient HT production, potentially providing a scalable biomanufacturing solution.
Methods
The study utilized an engineered E. coli chassis with an artificial synthetic pathway from 4-hydroxyphenylpyruvate. Promoter engineering of aroK, aroC, and tyrA was performed to enhance precursor supply. Overexpression of ARO10 and co-expression of DODC and TYO reduced l-DOPA accumulation. Cofactor engineering involved riboflavin metabolic genes and pntAB. The engineered strain was tested in a 5-L bioreactor with Fe2+ and ascorbic acid supplementation.
Results
The engineered E. coli strain achieved an HT titer of 9.25 g/L, a yield of 0.102 g/g glucose, and a productivity of 0.193 g/L/h. l-DOPA accumulation was reduced by 63.7% and 76.1% through targeted gene co-expression. Riboflavin gene overexpression increased HT production by 30.9%. Transcriptomic analysis showed upregulation of stress response genes, and overexpressing marR improved tolerance and production.
Interpretation
This study represents a significant advancement in microbial HT production, achieving the highest reported titer in E. coli. While the results are promising, the clinical and industrial applicability remains uncertain due to potential scalability and regulatory challenges. The findings align with previous efforts in metabolic engineering but offer enhanced production metrics.
Key findings
- HT titer of 9.25 g/L achieved in E. coli.
- Yield of 0.102 g/g glucose.
- Productivity of 0.193 g/L/h.
- 63.7% reduction in l-DOPA accumulation via DODC and TYO co-expression.
- 76.1% reduction in l-DOPA via LAAD expression.
- 30.9% increase in HT production with riboflavin gene overexpression.
Limitations
- E. coli model only, no human data.
- Potential scalability issues for industrial application.
- Regulatory challenges not addressed.
- Focus on metabolic engineering without clinical translation.