DICARBOXYLIC ACIDS PLATFORM CHEMICALS FOR VALORIZATION OF BIOREFINERY LIGNIN

Despite decades of effort, commercial development of biomass-to-biofuel conversion processes is still not an economically viable proposition. The emerging biomass refinery industry will inevitably generate an enormous amount of lignin as the solid waste stream. Development of selective biorefinery lignin-to-bioproducts conversion processes will play a pivotal role in significantly improving the economic feasibility and sustainability of biofuel production from renewable biomass. Due to the aromatic skeleton of lignin, most previous lignin valorization studies were limited to converting lignin to monomeric phenolics. Aromatic ring opened structures such as dicarboxylic acids (DCA) have been overlooked, though commonly observed during conversion. This thesis presents a new pathway for producing DCA as a new group of platform chemicals for lignin valorization, and specifically aims to develop a systematic understanding of the reaction mechanisms and to identify the key hurdles to optimizing conversion. To achieve this goal, a variety of oxidant and catalyst combinations were screened for oxidative depolymerization and conversion. A set of representative biorefinery lignin obtained from various commercial biorefineries for testing; the lignin samples were fully characterized by a number of selected analytical techniques. Representative monomeric and dimeric model compounds were used to help identify key intermediates and interpret the reaction mechanisms. Statistical analysis methods were developed as a new approach for providing quantitative guidance in lignin depolymerization research by relating and predicting lignin structure and reactivity. Techno-economic analysis (TEA) was conducted to direct future work toward addressing key bottlenecks in process costs. The new insights gained in this work inspired the development of novel catalytic oxidation pathways and processes to convert biorefinery lignin to DCA as a new group of platform chemicals/intermediates, enabling sustainable biofuel production from lignocellulosic biomass

New Insights Toward Quantitative Relationships between Lignin Reactivity to Monomers and Their Structural Characteristics

The heterogeneous and complex structural characteristics of lignin present a significant challenge to predict its processability (e.g., depolymerization, modifications etc.) tovaluable products. This study provides a detailed characterization and comparison of structural properties of seven representative biorefinery lignin samples derived from forest and agricultural residues, which were subjected to representative pretreatment methods. A range of wet chemistry and spectroscopy methods were applied to determine specific lignin structural characteristics such as functional groups, inter-unit linkages, and peak molecular weight. In parallel, oxidative depolymerization of these lignin samples toeither monomeric phenolic compounds or dicarboxylic acids were conducted, and the product yields were quantified. Based on these results (lignin structural characteristicsand monomer yields), we applied for the first time the multivariable linear estimation (MVLE) approach using R Statistics (an open-source programming language and software environment for statistical computing and graphics) to gain insight toward a quantitative correlation between lignin structural properties and their conversion reactivitytoward oxidative depolymerization to monomers

Characterization and Potential Applications of Milled Wood Lignin Obtained from Sugar Depot Biorefinery Process

This report aims at characterizing the structural properties of milled wood lignin and identifying its potential application

Peracetic Acid Depolymerization of Biorefinery Lignin for Production of Selective Monomeric Phenolic Compounds

Lignin is the largest source of renewable material with an aromatic skeleton. However, due to the recalcitrant and heterogeneous nature of the lignin polymer, it has been a challenge to effectively depolymerize lignin and produce high‐value chemicals with high selectivity. In this study, a highly efficient lignin‐to‐monomeric phenolic compounds (MPC) conversion method based on peracetic acid (PAA) treatment was reported. PAA treatment of two biorefinery lignin samples, diluted acid pretreated corn stover lignin (DACSL) and steam exploded spruce lignin (SESPL), led to complete solubilization and production of selective hydroxylated monomeric phenolic compounds (MPC‐H) and monomeric phenolic acid compounds (MPC‐A) including 4‐hydroxy‐2‐methoxyphenol, p‐hydroxybenzoic acid, vanillic acid, syringic acid, and 3,4‐dihydroxybenzoic acid. The maximized MPC yields obtained were 18 and 22 % based on the initial weight of the lignin in SESPL and DACSL, respectively. However, we found that the addition of niobium pentoxide catalyst to PAA treatment of lignin can significantly improve the MPC yields up to 47 %. The key reaction steps and main mechanisms involved in this new lignin‐to‐MPC valorization pathway were investigated and elucidated. A lignin to monomeric phenolic compounds (MPC) conversion method based on peracetic acid (PAA) treatment is been reported (see scheme). PAA treatment of two biorefinery lignin samples, diluted acid pretreated corn stover lignin (DACSL) and steam exploded spruce lignin (SESPL), led to complete solubilization and production of selective hydroxylated monomeric phenolic compounds (MPC‐H) and monomeric phenolic acid compounds (MPC‐A) in yields of 18 and 22 %

Protective effects of macrophage-specific integrin α5 in myocardial infarction are associated with accentuated angiogenesis

Abstract Macrophages sense changes in the extracellular matrix environment through the integrins and play a central role in regulation of the reparative response after myocardial infarction. Here we show that macrophage integrin α5 protects the infarcted heart from adverse remodeling and that the protective actions are associated with acquisition of an angiogenic macrophage phenotype. We demonstrate that myeloid cell- and macrophage-specific integrin α5 knockout mice have accentuated adverse post-infarction remodeling, accompanied by reduced angiogenesis in the infarct and border zone. Single cell RNA-sequencing identifies an angiogenic infarct macrophage population with high Itga5 expression. The angiogenic effects of integrin α5 in macrophages involve upregulation of Vascular Endothelial Growth Factor A. RNA-sequencing of the macrophage transcriptome in vivo and in vitro followed by bioinformatic analysis identifies several intracellular kinases as potential downstream targets of integrin α5. Neutralization assays demonstrate that the angiogenic actions of integrin α5-stimulated macrophages involve activation of Focal Adhesion Kinase and Phosphoinositide 3 Kinase cascades