We are excited to share the cover image of the November 18 issue of Biophysical Journal, capturing the complex association between biomass polymers—cellulose, hemicellulose, and lignin. The image is a molecular dynamics (MD) visualization of hydrothermal pretreatment in lignocellulosic biomass, showing cellulose fibril bundles in green and amorphous hemicellulose and lignin chains in brown and yellow, respectively.

This visualization highlights a research focus of our group on understanding the molecular-level organization in plant secondary cell walls. The assembly of lignocellulosic polymers in cell walls can be tuned with temperature and mixed solvents that interact with hydrophobic and hydrophilic cellulose, lignin, and hemicellulose surfaces. Co-solvent mixtures of organic solvents and water have effectively been shown to disrupt assembly through hydrogen bonding and hydrophobic interactions. Under favorable temperature and pressure conditions, these polymers can also be depolymerized in the presence of these co-solvents and a dilute acid catalyst.

The real-world implications of this research field are multifaceted. Manipulating polymers and their deconstruction is central to advanced biofuel production—breaking down cellulose to simple sugars and their fermentation to produce bioethanol, while converting lignin and hemicellulose into value-added co-products, MD simulation has uncovered fundamental interaction mechanisms and design principles for effective pretreatment, which have been corroborated by experiments. These insights are combined with artificial intelligence/ machine learning models to accelerate the discovery of novel solvent classes and optimize pretreatment processes.

This research contributes to the broader goal of a bio-based circular economy, in which lignocellulosic biomass can replace non-renewable resources as a sustainable energy source. In parallel, these insights help to control the self-assembly of nanocellulose to manufacture high-performance biomaterials.

To those outside the field, the work illustrates how molecular simulations can serve as a powerful tool to model sustainable bio-based materials and reveal the molecular interactions that govern their macroscopic behavior—advancing long-term sustainable energy and materials solutions affecting society.

Learn more about our work at https://cmb.ornl.gov and https://sfa-biofuels.ornl.gov.

— Jeremy C. Smith, Micholas Dean Smith, Shih-Hsien Liu, Shalini J. Rukmani, Mood Mohan, Yan Yu, and Monojoy Goswami