Adsorption of Bacteria\nExtracellular Polysaccharide\nSubstances on the Graphite (002) Surface: A DFT and MD Study

Understanding the principle of the bacteria–anode\nsurface\ninteraction can enhance electron transfer in microbial fuel cells\nand aid in antibiofouling. In this article, we investigate the adsorption\npropensity of common adhesins [<i>N</i>-acetylglucosamine\n(NAG), d-glucose, and alginate] found in microbial biofilms\non the surface of unmodified and modified graphite through density\nfunctional theory and molecular dynamics simulations. DFT results\nshowed that all the molecules could interact with the graphite surface,\nwith NAG (Δ<i>E</i><sub>gap</sub> = 3.677 eV) being\nthe most reactive molecule. The Fukui function results show that the\nmost active sites were located at O, C<sub>13</sub>, and N on the\nadsorbates. The optimum conditions were basic medium at 303 K across\nall systems. All adsorbates show energetically favorable adsorption,\nwith NAG showing the maximum adsorption energy irrespective of the\nmodification. The modified graphite system showed increased adsorption\ncompared to the unmodified graphite system. Electrostatic interactions,\nH-bonding, and π–π stacking or interactions are\nthe driving forces responsible for the chemical bond formation in\nthe adsorbates–adsorbent complexes. Altogether, this research\nprovides theoretical support for bacterial adhesin adsorption onto\ngraphite anodes and new ideas for studying bacteria–anode interactions\nin fuel cells, biofouling and antifouling, dental science, clean energy\nproduction, and wastewater treatment.