Bio-denitrification performance enhanced by graphene-facilitated iron acquisition

Area of Science:

• Environmental Microbiology
• Biotechnology
• Environmental Chemistry

Background:

• Biological denitrification is crucial for removing nitrate from contaminated sites and wastewater.
• Current methods often suffer from low efficiency, leading to nitrite accumulation and nitrous oxide emissions.
• Iron is vital for efficient denitrification, but intracellular iron levels in microbes are frequently insufficient.

Purpose of the Study:

• To investigate the use of graphene to enhance intracellular iron concentration in denitrifying microbes.
• To improve bio-denitrification efficiency and reduce intermediate accumulation.
• To explore the underlying mechanisms of graphene-mediated enhancement.

Main Methods:

• Utilizing graphene as a novel agent to facilitate iron transport into denitrifying bacteria.
• Quantifying nitrate removal, nitrite, and nitrous oxide generation with and without graphene.
• Analyzing the impact of graphene on microbial electron transfer, enzyme activity, gene expression, and intracellular energy levels.

Main Results:

• Graphene addition (50 mg/L) significantly improved nitrate removal efficiency by 67.3%.
• Nitrite and nitrous oxide generation were reduced by 49.0% and 63.9%, respectively.
• Graphene enhanced electron transfer, Fe-containing enzyme activity, and denitrifier growth by facilitating iron acquisition, increasing intracellular iron, proton-motive force, and ATP levels.

Conclusions:

• Graphene effectively enhances bio-denitrification by increasing intracellular iron concentrations in microbes.
• This method offers a promising strategy for efficient nitrate remediation with reduced byproducts.
• The study provides new insights into biological iron acquisition mechanisms and graphene's role in microbial processes.