H₂-driven reduction of CO₂ to formate using bacterial plasma membranes

Area of Science:

• Biocatalysis
• Nanotechnology
• Microbial Biochemistry

Background:

• Bacterial membranes can limit catalytic efficiency by controlling substance entry.
• Isolated bacterial plasma membranes offer potential as natural nanodevices for biocatalysis.
• Oxygen-stable [NiFe]hydrogenase and [Mo]formate dehydrogenase are key enzymes for CO2 conversion.

Purpose of the Study:

• To present a model system using isolated bacterial plasma membranes for efficient formate production.
• To investigate the catalytic efficiency and selectivity of a natural nanodevice for H2-driven CO2 conversion.
• To assess the stability of immobilized bacterial plasma membranes for formate synthesis.

Main Methods:

• Isolation of plasma membranes from Citrobacter sp. S-77.
• Integration of [NiFe]hydrogenase and [Mo]formate dehydrogenase into a natural catalytic nanodevice.
• Immobilization of membranes with multi-walled carbon nanotubes and encapsulation in gellan-gum hydrogel beads.

Main Results:

• The natural nanodevice catalyzed H2-driven conversion of CO2 to formate with a rate of 817 mmol·L−1·gprotein−1·h−1.
• The process demonstrated high selectivity and efficiency under mild conditions (30 °C, pH 7.0, 0.1 MPa).
• Immobilized catalyst remained stable over 10 repeated uses, indicating robustness.

Conclusions:

• Bacterial plasma membranes can function as efficient and selective natural nanodevices for formate production.
• Immobilization strategies enhance the stability and reusability of the biocatalyst.
• This study reports the first successful application of bacterial plasma membranes for efficient H2 and CO2 conversion to formate.