carbonate dissolving microbes bioenergy

Carbonate-Dissolving Microbes: A Game Changer for Sustainable Bioenergy

New Insights into the Global Carbon Cycle

A research team from the University of Nebraska-Lincoln has uncovered unknown microscopic contributors to the global carbon cycle, offering fresh insights into carbon dynamics and supporting sustainable bioenergy development.

The Role of Methanogens in Carbonate Dissolution

A recent published in Communications Earth & Environment is among the first to demonstrate that methanogens—microorganisms prevalent in low-oxygen environments such as lakes, wetlands and permafrost—can sustain their growth by tuilizing hydrogen and dissolving calcium carbonate, a widely abundant mineral on Earth. This metabolic activity generates methane, serving as both a biofuel and a potent greenhouse gas.

Early Demonstrations of Microbial Calcium Carbonate Dissolution

"This study provides one of the earliest demonstrations of microbial calcium carbonate dissolution occurring at elevated pH levels," said Karrie Weber, professor of Biological Sciences and Earth and Atmospheric Sciences.

Team Leadership and Collaborative Research Efforts

Under the leadership of Weber and Nicole Fiore, a lecturer and former graduate student in biological sciences, the team's research builds upon more than ten years of dedicated efforts at the university, with significant contributions from graduate and undergraduate students, along with postdoctoral researchers.

Challenging Longstanding Assumptions About Carbonate Stability

By identifying microorganisms capable of dissolving carbonate minerals, the research team has challenged the longstanding assumption that these minerals—holding approximately 80% of Earth's carbon—remain stable at higher pH levels. This newfound instability suggests that in environments where subsurface carbon is stored as carbonates and microbial life thrives, sequestered carbon could be transformed into methane, particularly within underground hydrogen energy reservoirs.

Assessing the Impact of Methanogens on Mineral Sequestration

"As we explore these strategies, we must consider whether methanogens are involved and how significantly they could undermine the intended effects of mineral sequestration," Fiore explained.

Investigating Methanogen Activity in a Controlled Environment

The study began with a mud sample collected from alkaline saline wetland soil in Lincoln. While the researchers were aware that any methanogens present would utilize hydrogen, it remained uncertain whether these microbes could also dissolve calcium carbonate to produce methane. To investigate, they established controlled culture conditions containing hydrogen and calcium carbonate, effectively filtering out microorganisms unable to metabolize the carbonate.

Key Findings: Microbial Community and Visualization

A small microbial community persisted through the culture process and its genomes were reconstructed by the researchers using genome-resolved metagenomics. This community included methanogens alongside five distinct bacterial species. Using Nebraska's CARS (coherent anti-Stokes Raman scattering) microscope, housed within the Laser Assisted Nano Engineering Lab, the team successfully visualized these microorganisms. Their findings revealed that the microbes adhered to the surface of the carbonate mineral.

Ensuring pH Control for Accurate Results

Unlike previous studies addressing this question, the team maintained strict control over the culture's pH—its level of acidity or basicity. This was crucial, as fluctuations in pH can alter the state of carbonate minerals. By stabilizing the pH, the researchers ensured that any observed mineral dissolution was primarily driven by microbial metabolism rather than chemical changes in the culture medium.

Implications for Bioenergy and Hydrogen Research

The metabolic activity of methanogens has significant implications for bioenergy research. With growing interest in natural hydrogen as a clean fuel, Nebraska has become a focal point, hosting the United States' first well drilled to explore naturally occurring hydrogen. According to Weber, understanding the extent to which microbial processes influence subsurface hydrogen reservoirs is crucial. Additionally, researchers are investigating whether methane produced by methanogens could serve as an alternative natural gas alongside subsurface hydrogen.

Future Directions: Global Research and Environmental Impact

According to Weber, the next phase of research involves identifying additional carbonate materials that methanogens can dissolve and detecting biosignatures that validate this process in natural environments, beyond controlled laboratory settings. The team hypothesizes that this phenomenon is occurring on a global scale, given that similar carbonate formations and methanogens coexist in numerous locations worldwide.

"While this research originates locally, its impact extends across the globe," said Weber.

Acknowledgments: Collaborative Efforts in Microbial Research

The interdisciplinary research team includes:

• Xi Huang — Research Assistant Professor of Electrical and Computer Engineering
• Yongfeng Lu — Lott Distinguished Professor in Electrical and Computer Engineering
• Nicole Buan — Professor of Biochemistry
• Dan Miller — Adjunct Faculty in Agronomy and Horticulture, USDA Research Microbiologist
• Sanjay Antony-Babu —  Former Postdoctoral Researcher
• Anthony Kohtz, Donald Pan, Caitlin Lahey — Former Students

Source

Unlock the Future of Microbial Research & Sustainable Energy!

Recent discoveries about methanogens and carbonate dissolution are reshaping our understanding of Earth's carbon cycle, bioenergy potential, and underground hydrogen reservoirs. As researchers uncover the role of microorganisms in methane production, the implications for climate science, renewable energy, and environmental sustainability are profound.

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