Understanding the molecular mechanisms of interactions between biochar and denitrifiers in N₂O emissions reduction: Pathway to more economical and sustainable fertilizers

Biochar application to topsoil has been repeatedly and independently reported to reduce N₂O emissions, yet the underlying mechanisms remain poorly understood. This study hypothesizes that biochar enhances the stability and catalytic activity of N₂O reductase enzymes in denitrifying bacteria, promoting the conversion of N₂O to N₂ during denitrification. Interactions between biochar and the N₂O reductase enzyme (PsN₂OR) from the denitrifying bacterium Pseudomonas stutzeri were investigated through molecular dynamics simulations. The obtained results firstly revealed that biochar stabilizes this periplasmic enzyme in the aqueous solution via hydrophobic and hydrophilic interactions. Specifically, π–π stacking and hydrophobic interactions reduce the thermal fluctuations of hydrophobic amino acids, lowering entropy and improving enzymatic efficiency. Additionally, biochar adsorbs N₂O molecules, facilitating their delivery to the active site of the enzyme and enhancing the reaction rate. Deeper understandings of molecular interactions open new pathways in developing biochar-based fertilizers with slower, more economically and more environmentally favorable release of nutrients. This new type of fertilizers creates new opportunities for the biochar market, positioning it as a valuable tool for carbon sequestration and the mitigation of N₂O emissions.