Study on Molecular Structure Model and Reactivity of Spent Mushroom Substrate: Experiment and Simulation

The infrastructure features of the spent mushroom substrate (SMS) were detected and explored based on experimental data acquired from Fourier Transform Infrared Spectroscopy, Pyrolysis–Gas Chromatography/Mass Spectrometry as well as Thermogravimetric Analysis. Further, molecular simulation methods were combined with diverse testing technologies to build the 2D and associated 3D models from cellulose, hemicellulose, and lignin. Eventually, a rational 3D model was constructed for SMS using geometry optimization calculations and annealing dynamics simulations. According to the Mulliken population analysis and electron density analysis, the π-π conjugation effect of the aromatic ring structures was influenced by the oxygen atoms, thus, resulting in the electron accumulation on these oxygen atoms. At the same time, oxygen exhibited a greater electronic charge density and reactivity in the Furan ring and pyran ring structures in contrast to other atoms. Furthermore, the molecular orbitals for HOMO and LUMO were computed to check the chemical reaction characteristics of the SMS. According to the HOMO–LUMO energy gap, the structure of the polycyclic aromatic hydrocarbons provided reaction sites for the reaction and played a key role in chemical bond breaking.Graphical Abstract