Formate as an intermediate in the bovine rumen fermentation

Area of Science:

• Rumen microbiology
• Biogeochemical cycles
• Microbial metabolism

Background:

• Formate is a key intermediate in anaerobic microbial ecosystems.
• Understanding formate metabolism is crucial for comprehending rumen function and methane production.

Purpose of the Study:

• To quantify formate production and utilization in bovine rumen contents.
• To determine the Michaelis constants (K(m)) for formate and hydrogen conversion to methane.
• To elucidate the role of non-methanogenic microbes in formate metabolism.

Main Methods:

• In vitro incubation of whole bovine rumen contents.
• Measurement of formate concentration and turnover rates.
• Analysis of methanogenesis rates in relation to substrate concentrations.
• Pure culture studies with Methanobacterium ruminantium.

Main Results:

• Average formate production and utilization was 11 µmoles/g/hr.
• Intercellular formate concentration averaged 12 nmoles/g, while total rumen formate was up to 1000 times higher.
• Michaelis constants (K(m)) for formate and hydrogen conversion to methane were estimated at 30 nmoles/g and 1 nmole/g, respectively.
• Non-methanogenic microbes were implicated in metabolizing intercellular formate.

Conclusions:

• Non-methanogenic microbes play a significant role in metabolizing intercellular formate within the rumen.
• Carbon dioxide and hydrogen are the primary substrates for rumen methanogenesis.
• Formate contributes approximately 18% to the total methane production in the bovine rumen.