Chemical Transformations of Buddleja davidii Lignin during Ethanol Organosolv Pretreatment

Abstract

Detailed chemical structural elucidation of ethanol organosolv lignin (EOL) of Buddleja davidii was performed to determine the fundamental structure released from an ethanol organosolv pretreatment (EOP). Several nuclear magnetic resonance (NMR) techniques were used to analyze the structure of EOL, including quantitative 13 C, 31 P NMR, and qualitative DEPT-135 13 C, 2D 1 H-13 C correlation NMR. As revealed by NMR, the aryl-O-ether linkage (β-O-4 0 ) of lignin was extensively cleaved via homolysis during pretreatment and led to the formation of stilbene structures. Other linkages, such as resinol (β-β 0 ) and phenylcoumaran (β-5 0 ), were resistant to degradation. The high degree of condensation of EOL indicated that condensation reactions occurred but did not impede the delignification efficiency of EOP. Both guaiacyl and syringyl lignin were found to be reactive toward condensation during pretreatment. The results from gel-permeation chromatography showed that the degree of polymerization (DP) of lignin significantly decreased by ∼85%, facilitating lignin solubilization in ethanol.

Structural Characterization of Lignin in Wild-Type versus COMT Down-Regulated Switchgrass

“…The signal assignments and quantitative analysis of 13 C NMR spectra of lignin were performed following literature reports (Higuchi et al, 1967;Marita et al, 2001;Ralph et al, 2001;Capanema et al, 2005;Pu et al, 2005;Hallac et al, 2010). The signals from both guaiacyl and syringyl units were readily observed from the G 2 , G 6 , and S 2/6 signals centered~δ 109.5, 119.1, and 104.6 ppm, respectively.…”

Effect of structural changes of lignin during the autohydrolysis and organosolv pretreatment on Eucommia ulmoides Oliver for an effective enzymatic hydrolysis

“…To overcome the biological recalcitrances of the biomass, various pretreatment methods have been developed (Chandra et al, 2007). However, the basic chemical mechanisms mentioned in pretreatment processes played a vital role in the next step of selecting a suitable technology for the viable production of second-generation bioethanol (Hallac et al, 2010). To improve the overall effectiveness of bioethanol production, all components of biomass (such as agriculture waste, starch of plant and lignocellulose substance as raw materials, etc.)…”

“…It is an amorphous polymer, comprising of different linkages, such as b-O-4, a- O-4, b-b, b-5, b-1, 5-5, 4-O-5, and dibenzodioxocin ones, depending on the biomass species (Pu et al, 2008). The lignin in the plant cell wall have a role in providing structural support, impermeability, and resistance against microbial attack (Hallac et al, 2010). Whereas, the existence of lignin affects the efficiency of pretreatment process in further applications (e.g.…”

“…Traditionally, this process was used to delignify wood chips for the production of chemical pulp and lignin. Nowadays, EOP process is applied to lignocellulosic biomass to obtain more reactive cellulose-rich substrate and result in a high conversion of cellulose to glucose (more than 90%) (Hallac et al, 2010). In fact, the efficient conversion was in part due to the limited amount of residual lignin after EOP .…”

Homogeneous Esterification Mechanism of Bagasse Modified with Phthalic Anhydride in Ionic Liquid, Part 3: Structural Transformation of Lignins

“…5. Based on the previous publications (Hallac et al 2010;Wang et al 2012;Cheng et al 2013;Mbotchak et al 2015), the primary correlations were well assigned. The HSQC spectra of lignins were divided into two regions: aromatic region (δH 5.8 to 8.0 ppm, δC 95 to 145 ppm) and side-chain region (δH 2.5 to 6.0 ppm, δC 50 to 90 ppm).…”