Exploring biological mechanisms and materials to enable the bioeconomy through computational physics
ABSTRACT: Advances in physics tools and techniques have been fundamental in the study of biological processes at diverse length and timescales, with molecular simulation in particular probing length and timescales that would otherwise be inaccessible. This computational microscope can be applied to topics surrounding sustainability, applying simulation tools to better understand biological material properties at the nanoscale in the service of integrating biopolymers into industry. This includes lignin, an aromatic heteropolymer found in the secondary cell walls of terrestrial plants. Due to its abundance, lignin is being evaluated as a feedstock for many bioproducts, but its utilization has been hampered by its heterogeneity at the molecular level. Recent progress in molecular simulation tools have enabled lignin simulation, elucidating critical parameters for under-standing lignin dynamics and structure within relevant molecular environments. These simulations quantify lignin nanostructure and polymer expansion within specific solvent environments, its affinity to cellulose, and its permeability across biological membranes. In each case, the results provide actionable intelligence to improve lignin utilization within the emerging bioeconomy. Solvent with modest polarity are shown to be optimal solvents for lignin. The swelling induced by these solvents reduces the contact surface with other biopolymers, reducing their affinity and likely improving the separations performance. The observed high permeability for small uncharged lignin compounds indicates that passive diffusion is likely enough for microbes to uptake lignin fragments, obviating the need to engineer specific transport proteins for lignin. These results pave the way for future work in developing new materials from lignin.