Adsorption kinetics between tetrodotoxin and peptidoglycan derived from lactic acid bacteria

Peptidoglycan (PG) is a key component that enables lactic acid bacteria to remove tetrodotoxin (TTX). However, the adsorption behaviors and interaction mechanisms between PG and TTX remain unclear. Herein, three types of PGs (A3α-PG, A1γ-PG, and A4α-PG) were used to treat TTX. After treatment, the residual TTX content was reduced by 82.85 %-84.73 %, and TTX toxicity decreased by 87.30 %-93.02 %, indicating that the three PGs could effectively remove TTX. Adsorption kinetics analysis showed that the adsorption of TTX by the three PGs conformed to the quasi-second-order (R² > 0.99) and the Freundlich (R² > 0.99) models. These findings suggest that the adsorption behavior between PG and TTX involves a coexistence of chemical adsorption and multilayer physical adsorption modes. Furthermore, molecular docking simulations and quantum chemical calculations clarified that the adsorption interaction between PG and TTX involved physical interactions mediated by hydrophobic interactions and van der Waals forces, as well as chemical interactions mediated by strong hydrogen bonds (1.352 Å) with a Mayer bond order of 0.2687. This study elucidates the mechanism of PG in removing TTX, providing a theoretical basis for developing more efficient TTX adsorbents and detoxification technologies in the future. Further research on the adsorption kinetics and interactions between PG and TTX may offer methodological references and novel insights into the adsorption mechanisms of other biological molecules.