Critical analysis of peptidoglycan structure of Lactobacillus acidophilus for phthalate removal

Our previous studies have shown that lactic acid bacteria (LABs) can bind and remove di-n-butyl phthalate (DBP), diethyl phthalate, and dioctyl phthalate; three ubiquitous environmental phthalate contaminants. In this study, Lactobacillus acidophilus NCFM was chosen to study the DBP binding mechanism. We found that the three-dimensional structure of the bacterial cell wall, including the carbohydrates and proteins, was essential for DBP adsorption. Peptidoglycan was the main binding component in the cell wall (80.71%), and binding sites exposed to DBP were C-N, N-H, O-H, and C-O bonds. Molecular dynamic (MD) studies demonstrated that hydrophobic interaction plays an important role in DBP adsorption, the chemical sites that influenced the binding in the peptidoglycan model were O2, O3>N1, N2, N3>O1, O4, and the form of adsorption force included hydrogen bonding force, electrostatic force, and van der Waals forces. These theoretical data from the MD simulation were consistent with the experimental results in terms of the ability of this bacterium to bind DBP, so the MD simulation proposed a new way to investigate the mechanisms of phthalate binding to LABs.