Adsorption of Bacteria Extracellular Polysaccharide Substances on the Graphite (002) Surface: A DFT and MD Study

Understanding the principle of the bacteria-anode surface interaction can enhance electron transfer in microbial fuel cells and aid in antibiofouling. In this article, we investigate the adsorption propensity of common adhesins [N-acetylglucosamine (NAG), d-glucose, and alginate] found in microbial biofilms on the surface of unmodified and modified graphite through density functional theory and molecular dynamics simulations. DFT results showed that all the molecules could interact with the graphite surface, with NAG (ΔE _gap = 3.677 eV) being the most reactive molecule. The Fukui function results show that the most active sites were located at O, C₁₃, and N on the adsorbates. The optimum conditions were basic medium at 303 K across all systems. All adsorbates show energetically favorable adsorption, with NAG showing the maximum adsorption energy irrespective of the modification. The modified graphite system showed increased adsorption compared to the unmodified graphite system. Electrostatic interactions, H-bonding, and π-π stacking or interactions are the driving forces responsible for the chemical bond formation in the adsorbates-adsorbent complexes. Altogether, this research provides theoretical support for bacterial adhesin adsorption onto graphite anodes and new ideas for studying bacteria-anode interactions in fuel cells, biofouling and antifouling, dental science, clean energy production, and wastewater treatment.