Improving trans-cinnamic acid production in a model cyanobacterium

Area of Science:

• Synthetic biology and metabolic engineering of cyanobacteria.
• Biotechnology for renewable chemical production.
• Bioprocess engineering for microbial fermentation.

Background:

• trans-Cinnamic acid (tCA) is a valuable precursor for pharmaceuticals, polymers, and cosmetics.
• Current tCA production relies on fossil fuels or expensive plant extraction.
• Cyanobacteria offer a sustainable platform for metabolite production using CO2 and sunlight.

Purpose of the Study:

• To develop a high-titer cyanobacterial strain for renewable trans-Cinnamic acid (tCA) production.
• To optimize tCA biosynthesis in Synechocystis sp. PCC 6803 using an inducible promoter system.
• To evaluate tCA production under various light conditions and in photobioreactors.

Main Methods:

• Engineered Synechocystis sp. PCC 6803 (S. 6803) to express a plant phenylalanine ammonia lyase (PAL) gene under an inducible promoter.
• Cultivated engineered strains in shake flasks with constant and cyclic light, and in environmental photobioreactors (ePBRs).
• Assessed tCA production and culture density over 14 days under different cultivation conditions.

Main Results:

• Achieved a four-fold increase in tCA production (~500 mg L⁻¹) compared to previous studies in S. 6803.
• Demonstrated 30-50% improved average tCA production per culture density (60 mg·L⁻¹·OD730⁻¹) in ePBRs.
• Successfully scaled tCA bioproduction to 500 mL culture volumes.

Conclusions:

• The developed high-titer cyanobacterial strain significantly enhances renewable tCA bioproduction.
• An inducible promoter system effectively controls tCA production in S. 6803.
• This study validates cyanobacteria as a robust biological factory for sustainable chemical synthesis.