Molecular Dynamics Simulation in the Delignification Process by Low Transition Temperature Mixtures (LTTM) Solvents Using the GROMACS Application

Abstract

Low Transition Temperature Mixture (LTTM) is one of green solvents that can be widely used for many applications such as delignification in the biomass pretreatment process. The aim of molecular dynamics simulation of lignin in LTTM is to predict the potential composition of LTTM in the delignification process application then to analyze which the molecular interactions affecting. Study of the delignification process was carried out by analyzing the Solvent Accessible Surface Area (SASA) and lignin’s radius of gyration in LTTM using GROMACS application. During the simulation, GROMOS was chosen as a force field because it had been validated for the LTTM simulation in the previous study. The used coordinate files consisted of the lignin model in the form of 15 syringyl units and LTTM molecules with compositions lactic acid-sucrose (LS), malic acid-sucrose-water (MSW), and tartaric acid-sucrose-water (TSW). Based on the result analysis of simulation, molecular structural changes, lignin which dissolved in LS is predicted to have the best potential composition for delignification compared to TSW or MSW. Van der Waals interactions, electrostatic interactions, or the total of both (nonbonding interactions) affect the changes in the conformation of lignin molecules in LTTM. However, electrostatic interactions tend to give more effect on the radius of gyration changes compared to van der Waals interactions. Meanwhile, the number of hydrogen bonds between the lignin molecule and LTTM has no correlation on the conformation of lignin.