Modeling the Conformational Preference of the Lignocellulose Interface and Its Interaction with Weak Acids

Area of Science:

• Biomass Conversion and Utilization
• Computational Chemistry
• Materials Science

Background:

• Lignocellulose, a complex biopolymer, presents challenges in processing due to its intricate structure.
• Understanding the interactions between cellulose (sugar) and lignin components is crucial for efficient biomass conversion.
• Existing methods for lignocellulose processing often rely on harsh chemicals, necessitating exploration of milder alternatives.

Purpose of the Study:

• To investigate the conformational landscape of sugar-lignin linkages in lignocellulose models.
• To identify low-energy isomers and characterize their structural features.
• To evaluate the potential of weak acids as processing agents for lignocellulose.

Main Methods:

• Utilized multistage computational screening protocols to identify lowest-energy isomers of glucose and paracoumaryl alcohol models.
• Employed a hierarchy of quantum chemical methods, including DFTB3/3ob, SCANh/6-31+G(2d,p), DSD-PBEP86/ma-def2-TZVP, and CCSD(T)/CBS.
• Incorporated machine learning potentials (London and Axilrod-Teller-Muto) to accelerate the screening process.

Main Results:

• Identified low-energy conformers predominantly stabilized by hydrogen bonding between sugar and lignin moieties.
• Revealed strong interactions between covalently bonded sugar-lignin models and weak acids, particularly at the sugar-O-lignin linkage.
• Found that dihydrogen citrate and similar acids exhibit significant binding affinity.

Conclusions:

• Hydrogen bonding plays a critical role in stabilizing sugar-lignin structures within lignocellulose.
• Weak acids, especially dihydrogen citrate, represent promising, potentially milder alternatives to traditional agents like bisulfite (HSO3-) for lignocellulose processing.
• Computational modeling provides an effective strategy for exploring biomass component interactions and identifying novel processing agents.