Methanogenic population dynamics during semi-continuous biogas fermentation and acidification by overloading.

Area of Science:

• Microbiology
• Biotechnology
• Environmental Science

Background:

• Biogas reactors are crucial for renewable energy production.
• Understanding the methanogenic community is key to optimizing biogas production.
• Process instability in biogas reactors can lead to reduced efficiency.

Purpose of the Study:

• To investigate the methanogenic community dynamics in a biogas reactor during startup and under acidification conditions.
• To evaluate the reliability and accuracy of quantitative real-time PCR (Q-PCR) for monitoring microbial communities.
• To identify potential biological indicators of biogas reactor instability.

Main Methods:

• A mesophilic, continuously stirred tank reactor fed with maize silage was operated at increasing organic loading rates (OLRs).
• Gas production and organic acid composition were measured.
• Methanogenic community structure was analyzed using 16S rDNA-based Q-PCR to quantify key microorganisms.

Main Results:

• Hydrogenotrophic Methanobacteriales dominated at higher OLRs (>=3.7 g DOM l(-1) day(-1)).
• Aceticlastic Methanosaetaceae predominated at lower OLRs but disappeared at OLRs >=4.1 g DOM l(-1) day(-1).
• A dramatic increase in propionate concentration indicated digester acidification, coinciding with Methanosaetaceae disappearance. Q-PCR accuracy showed potential variation within one log cycle.

Conclusions:

• The absence of Methanosaetaceae can serve as a biological indicator for biogas reactor process instability.
• Q-PCR is a valuable tool for monitoring methanogenic communities in biogas reactors.
• Insights into methanogen abundance can guide strategies for improving biogas reactor performance.