Lignin Valorization: Improving Lignin Processing in the Biorefinery

Abstract

Research and development activities directed toward commercial production of cellulosic ethanol have created the opportunity to dramatically increase the transformation of lignin to value-added products. Here, we highlight recent advances in this lignin valorization effort. Discovery of genetic variants in native populations of bioenergy crops and direct manipulation of biosynthesis pathways have produced lignin feedstocks with favorable properties for recovery and downstream conversion. Advances in analytical chemistry and computational modeling detail the structure of the modified lignin and direct bioengineering strategies for future targeted properties. Refinement of biomass pretreatment technologies has further facilitated lignin recovery, and this coupled with genetic engineering will enable new uses for this biopolymer, including low-cost carbon fibers, engineered plastics and thermoplastic elastomers, polymeric foams, fungible fuels, and commodity chemicals.

Direct rate assessment of laccase catalysed radical formation in lignin by electron paramagnetic resonance spectroscopy

“…Hence, a significant potential exists for exploitation of lignin to create value added products without compromising internal process requirements of biorefineries, and development of e.g. aromatic derived chemicals or functionalized polymeric materials by various catalytic technologies has already been reported in the literature [2][3][4][5][6].…”

“…It is considered useless for biomass processing and in current biorefineries residual lignin is combusted for internal energy consumption. However, it has been estimated that a surplus of lignin of 60% beyond what is needed for process energy is present in today's cellulosic ethanol biorefineries [2]. Hence, a significant potential exists for exploitation of lignin to create value added products without compromising internal process requirements of biorefineries, and development of e.g.…”

“…In the plants, lignin is synthesized via coupling reactions between primarily three phenylpropanoid subunits, p-coumaryl alcohol (H-unit), coniferyl (guaiacyl) alcohol (G-unit), and syringyl alcohol (S-unit), to form a hydrophobic, insoluble network linked together by ether and carbon-carbon bonds [1,2]. The lignin network essentially surrounds the plant polysaccharides in each plant cell wall and typically constitutes 10-30% of lignocellulosic plant material [1].…”

Physicochemical Characterisation of Technical Lignins for Their Potential Valorisation

“…It is expected that in the near future, the advent of new biorefineries, which convert cellulosic biomass into transportation biofuels, will introduce an excess supply of various lignins into the process streams, besides the substantial amounts of lignin produced annually from pulping [1]. This turns lignin into a potentially highly available and accessible renewable feedstock for the synthesis of bulk aromatic and phenolic compounds [2].…”

Depolymerization Pathways for Branching Lignin Spirodienone Units Revealed with ab Initio Steered Molecular Dynamics

“…Lignocellulosic biomass [1][2] has captured much interest in recent years [3][4][5][6] as a potential cheap and renewable energy source 7 . Lignin, in particular, is a biopolymer 8 (20-30% of biomass by weight 9 ) with high structural heterogeneity that has historically limited its utilization to the fast pyrolysis [10][11] generation of low-grade and volatile bio oil 2 of moderate value 12 .…”