The physiology of trace elements in biological methane production

Area of Science:

• Microbiology
• Biotechnology
• Biochemistry

Background:

• Trace elements are crucial for microbial metabolism, particularly in methanogens.
• Understanding trace element requirements is key to optimizing biological methane production.

Purpose of the Study:

• To investigate the trace element requirements of Methanothermobacter okinawensis and Methanothermobacter marburgensis.
• To compare the growth and methane production capabilities of these two methanogens under various cultivation conditions.
• To optimize conditions for enhanced carbon dioxide-based biological methane production.

Main Methods:

• In silico genomic analysis of trace element transport systems and Wood-Ljungdahl pathway enzymes.
• Closed batch and fed-batch cultivation experiments to assess growth and methane production.
• Optimization of cultivation parameters including medium, trace element, and sulfide dilution rates, and gas inflow rates.

Main Results:

• Genomic differences were identified between M. okinawensis and M. marburgensis related to trace element metabolism.
• M. okinawensis showed increased specific growth rate (µ) and methane production rate (MER) with higher trace element concentrations.
• M. marburgensis exhibited higher µ and MER in fed-batch cultivation, leading to its selection for further optimization.
• Optimized exponential fed-batch cultivation of M. marburgensis achieved an MER of 476 mmol L^-1h^-1 and µ of 0.69 h^-1.

Conclusions:

• Methanothermobacter marburgensis is a promising candidate for efficient CO₂-based biological methane production.
• Optimized trace element and cultivation strategies significantly enhance methane yield.
• Further research into trace element optimization can improve the viability of methanogenic biogas production.