Systems metabolic engineering for hydroxytyrosol production in Escherichia coli

Area of Science:

• Metabolic Engineering and Synthetic Biology
• Biotechnology and Bioprocessing
• Microbial Fermentation

Background:

• Hydroxytyrosol (HT), a key olive oil component, is challenging to biosynthesize microbially due to its chemical properties.
• Existing methods for HT production face limitations in yield and scalability.
• Developing engineered microbial strains is crucial for efficient and sustainable HT production.

Purpose of the Study:

• To engineer Escherichia coli (E. coli) for the de novo biosynthesis of hydroxytyrosol (HT).
• To optimize fermentation strategies for enhanced HT production and stability.
• To establish a foundation for the large-scale production of HT and its derivatives.

Main Methods:

• Modular engineering of the HT biosynthetic pathway in E. coli using genes from E. coli and Saccharomyces cerevisiae.
• Metabolic flux optimization, including pathway attenuation and reinforcement, and gene copy number adjustment.
• Strain engineering to improve cofactor supply (NADPH, FADH2) and implemented controlled fermentation strategies (pH, dissolved oxygen, fed-batch supplementation with Vitamin B1).

Main Results:

• Successfully established a de novo HT biosynthetic pathway in E. coli.
• Generated a high-producing strain (HT32-3) through comprehensive metabolic engineering.
• Achieved a final HT titer of 9.22 g/L in a 5 L bioreactor using optimized fermentation conditions.

Conclusions:

• The study presents a practical and effective strategy for engineering microbial strains for high-value compound production.
• Developed fermentation strategies mitigate oxidative degradation and cofactor limitations, significantly improving HT yield and retention.
• The engineered strain and fermentation process lay the groundwork for the industrial-scale production of HT and related tyrosine derivatives.