Biorefinery Processing of Diverse Protolignins to Assist Biorefinery Lignin Valorization

摘要

Carbohydrate-derived products are currently the primary and sole output of biorefinery processes. Biorefinery lignin co-products, if properly developed, are expected to supplement biorefinery income and reduce reliance upon the market of a single output product. A broad survey of biomasses have been comprehensively analyzed, focusing upon differing lignin's responses to biorefinery processing. Characterization results are intended to elucidate biorefinery lignin properties and aid biomass selection for biorefineries looking to valorize lignin.;The pretreatment utilized in the investigated cellulase-based biorefinery process was autohydrolysis. Autohydrolysis is a simple pretreatment that utilizes only water, temperature, and pressure to facilitate biomass degradation and deconstruction. Chemical degradation is enabled by cleavage of hemicellulosic acetates to produce acetic acid in the water hydrolyzate ("autohydrolyzate").;Autohydrolysis was found to render minor quantities of hardwood and non-wood lignin soluble in autohydrolyzate. A method for soluble lignin segregation was developed and applied across all studied biomasses in order to elucidate this mostly unknown biorefinery lignin fraction. Autohydrolyzate-soluble lignin is of particular interest based upon its low molecular weight, low polydispersity, high phenolic functionality, and aqueous solubility. These properties are ripe for innovation of co-products based upon autohydrolyzate-soluble lignin. In addition, sequestration of autohydrolyzate-solute lignin backhandedly revealed a means of separating lignin from hemicellulosic xylooligosaccharides. These oligosaccharides are also attractive biorefinery co-products based on the existing market for similar non-digestible oligosaccharide food additives.;Insoluble residues after pretreatment and cellulolytic hydrolysis are lignin enriched due to the carbohydrate-targeting unit operations preceding its generation. This material has been partially characterized to describe it relative to protolignin, with conclusions being drawn that identify key markers in protolignin that are most influential upon residual lignin's chemical and molecular properties. For both hardwood and non-wood, trends have been identified that relate lignin reactivity with monolignol constituency.