Developing a robust biomethanation process by improving oxygen tolerance of Methanothermobacter wolfeii strain BSEL

Area of Science:

• Biotechnology
• Microbial Engineering
• Renewable Energy

Background:

• Biomethanation converts CO2 and H2 to renewable natural gas (RNG).
• Methanogenic archaea are sensitive to oxygen (O2), limiting RNG production in biogas facilities.
• Oxygen contamination can destabilize biomethanation processes due to intermittent oxidative conditions.

Purpose of the Study:

• To improve oxygen tolerance in the hydrogenotrophic methanogen Methanothermobacter wolfeii BSEL.
• To develop a more robust biocatalyst for large-scale biomethanation and biogas upgrading.
• To reduce reliance on strict anaerobic conditions for biomethanation.

Main Methods:

• Adaptive laboratory evolution (ALE) was applied in serial batch and continuous cultures.
• Methanothermobacter wolfeii BSEL was subjected to increasing oxygen concentrations.
• Bioreactor performance was monitored under various oxygen levels and oxidation-reduction potentials (ORP).

Main Results:

• An evolved Methanothermobacter wolfeii culture demonstrated tolerance to 2000 ppmv O2 in batch cultures.
• The evolved culture maintained methanogenesis at up to 3600 ppmv O2 in a continuous bioreactor.
• High methane (CH4) productivity was sustained despite oxygen exposure and changes in cell morphology (decreased size, biofilm formation).

Conclusions:

• Methanothermobacter wolfeii can adapt to elevated oxygen levels in continuous cultivation.
• This adaptation maintains high methane production, expanding the operational redox range for biomethanation.
• The findings support more resilient and scalable biomethanation processes for renewable natural gas production.