(66a) Mechanism-Based Lignin Bioprocess and Biomaterial Design

Lignin is one of the most abundant biopolymers on earth. Despite the abundance, lignin remains primarily a waste stream from paper, pulping, and biorefining industries. The utilization of lignin as a fungible material is fundamental to the sustainable development of our society. Nevertheless, the limited understanding of fundamental structure-property relationship between lignin chemistry and material/product properties have hindered the development lignin processing and materials. Our interdisciplinary team have advanced the understanding how lignin chemistry impacts processibility and material properties. First, we have revealed that lignin processing into smaller molecular weight, monomer-containing, and hydroxyl group-enriched fractions will significantly improve the bioprocessibility. Based on the fundamental understanding, we have designed a ‘plug-in’ module to transform the conventional pretreatment technologies into integrated biorefinery for both carbohydrate and lignin conversion. In particular, the innovative biorefinery design has enabled lignin processing into PHA to reach market-competitive prices. Second, we have discovered that lignin molecular weight, uniformity, linkage profile, and functional groups could all impact the lignin-derived biomaterials' properties, including carbon fibers, nanoparticles, recyclable plastic blends, and pavement materials. For example, the higher molecular weight, better uniformity, and more linear linkages could improve carbon material properties. The fundamental understanding has guided the lignin process design to derive the type of lignin to achieve highest reported tensile strength for lignin carbon fiber. This new type of lignin can also promote the performance of plastic blends, empowering quality UV-shading biomaterials. The lignin with more condensed structure benefits the stability and size selection for nanoparticles. The lignin functional groups and molecular weight also impact the interaction with asphaltene, in a way that lignin can be tailored to derive asphalt binder modifier with unique properties. Overall, based on the fundamental understanding, we have developed various processes to transform lignin into a precursor for broader biomaterial applications.