Sequential UV mutagenesis and CO₂ acclimation reprogram metabolic carbon allocation in Euglena gracilis

Area of Science:

• Microbiology
• Biotechnology
• Metabolic Engineering

Background:

• Euglena gracilis is a candidate for carbon dioxide (CO2) bioutilization.
• Its metabolic responses to high CO2 levels remain poorly understood.
• Optimizing CO2 utilization requires understanding metabolic shifts.

Purpose of the Study:

• To evaluate the LE-ZW mutant of Euglena gracilis under elevated CO2 conditions (5% and 10%).
• To characterize the metabolic reprogramming and carbon flux redirection in response to varying CO2 concentrations.
• To assess the potential of LE-ZW for industrial CO2 mitigation and bio-production.

Main Methods:

• UV mutagenesis and CO2 acclimation to generate the LE-ZW mutant.
• Cultivation of LE-ZW under 5% and 10% CO2.
• Measurement of cell density, photosynthetic carbon fixation, and biomass composition (lipids, paramylon, proteins).
• Transcriptomic and metabolomic analyses to identify gene and metabolite changes.
• Enzyme activity assays (superoxide dismutase).

Main Results:

• LE-ZW exhibited higher cell density and photosynthetic carbon fixation at 10% CO2 compared to 5% CO2.
• Carbon allocation shifted from lipid accumulation under 5% CO2 to paramylon accumulation under 10% CO2.
• High CO2 induced upregulation of genes involved in the Calvin cycle and GS-GOGAT pathway, alongside increased protein content.
• Metabolic reprogramming involved key regulatory hubs controlling carbon flux, and enhanced antioxidant defense was observed.

Conclusions:

• The LE-ZW mutant demonstrates significant metabolic flexibility and enhanced performance under elevated CO2.
• Integrated regulation of carbon-nitrogen metabolism and redox homeostasis was observed.
• LE-ZW shows strong potential for industrial CO2 mitigation and the production of bio-based products.