Effects of overexpression on lignin and cell wall characteristics in transgenic hybrid aspen.

In plant cell walls, lignin, cellulose, and the hemicelluloses form intricate three-dimensional structures. Owing to its complexity, lignin often acts as a bottleneck for the efficient utilization of polysaccharide components as biochemicals and functional materials. A promising approach to mitigate and/or overcome lignin recalcitrance is the qualitative and quantitative modification of lignin by genetic engineering.

Synergetic effect of fungal pretreatment and lignin modification on delignification and saccharification: a case study of a natural lignin mutant in mulberry.

Background: Fungal pretreatment for partial separation of lignocellulosic components may reduce lignocellulose recalcitrance during the production of biofuels and biochemicals. Quantitative and qualitative modification of plant lignin through genetic engineering or traditional breeding may also reduce the recalcitrance. This study was conducted to examine the effects of combining these two approaches using three white rot fungi and mulberry wood with an altered lignin structure.

Corrigendum: Enhancing enzyme-mediated cellulose hydrolysis by incorporating acid groups onto the lignin during biomass pretreatment.

[This corrects the article DOI: 10.3389/fbioe.2020.

Fractionation of beech wood cell walls into digestible cellulose-rich residues and photoluminescent lignin-rich precipitates semi-flow hot-compressed water treatment with 2-naphthol.

Utilization of cell wall components of woody biomass has attracted attention as alternatives for fossil fuels towards a sustainable society. A semi-flow hydrothermal treatment was used to fractionate the beech () wood into cellulose-rich residues and lignin-rich precipitates. The enzymatic saccharification of the cellulose component in the residue was enhanced significantly because the preferential delignification from the secondary wall increased enzyme accessibility.

Solubilization of sulfuric acid lignin by ball mill treatment with excess amounts of organic compounds.

In order to improve the solubility of sulfuric acid lignin (SL) in ,-dimethylformamide (DMF), dry ball milling with excess amounts of additives such as l-tartaric acid was performed. Although the ball-milled SL without any additives was not soluble in DMF, when the SL was ball milled with an excessive amount of l-tartaric acid (the concentration of SL to be 0.1%), the dispersion and solubility of SL in DMF detected by the dynamic light scattering was greatly improved.

Influence of Proteins on the Lignin Decomposition Behavior of Japanese Cedar () Wood by Supercritical Methanol Treatment.

The effect of adding protein on the decomposition behavior of lignin in Japanese cedar under supercritical methanol conditions (270 °C/27 MPa) was studied. The Klason method was used to detect the lignin content in the insoluble residue following to a 30 min treatment. Adding either an animal (bovine serum albumin) or plant (soy) protein enhanced delignification from 50 to 65% of the lignin-based wt %.

Tunable Light Emission from Lignin: Various Photoluminescence Properties Controlled by the Lignocellulosic Species, Extraction Method, Solvent, and Polymer.

This report describes the tunable light emission from lignin, which was achieved by carefully selecting the lignocellulosic species, extraction method, solvent, and polymer. Lignins comprising various taxonomic species with distinct primary structures exhibited diverse photoluminescence (PL) intensities and spectral patterns. Investigations probing how the solvent affects the PL properties revealed that the PL quenching phenomenon originated from the decreasing distance between aromatic moieties (luminophores).

Topochemistry of the Delignification of Japanese Beech () Wood by Supercritical Methanol Treatment.

The topochemistry of Japanese beech () wood delignification was evaluated in this study following a supercritical methanol treatment (270 °C, 27 MPa). Ultraviolet microscopic analysis of the insoluble residue revealed that the lignin in the secondary wall was easily decomposed and removed because of the preferential cleavage of ether-type linkages. In contrast, the middle lamella lignin was initially resistant to supercritical methanol but eventually decomposed and was removed.

Enhancing Enzyme-Mediated Cellulose Hydrolysis by Incorporating Acid Groups Onto the Lignin During Biomass Pretreatment.

Lignin is known to limit the enzyme-mediated hydrolysis of biomass by both restricting substrate swelling and binding to the enzymes. Pretreated mechanical pulp (MP) made from Aspen wood chips was incubated with either 16% sodium sulfite or 32% sodium percarbonate to incorporate similar amounts of sulfonic and carboxylic acid groups onto the lignin (60 mmol/kg substrate) present in the pulp without resulting in significant delignification. When Simon's stain was used to assess potential enzyme accessibility to the cellulose, it was apparent that both post-treatments enhanced accessibility and cellulose hydrolysis.

Alkaline sulfonation and thermomechanical pulping pretreatment of softwood chips and pellets to enhance enzymatic hydrolysis.

To assess the impact of alkalinity on sulfonation and the enzyme-mediated hydrolysis of softwood cellulose, Lodgepole pine chips were impregnated with 8% sodium sulfite and increasing loadings of sodium carbonate before thermomechanical pulping. It was apparent that alkali addition enhanced lignin sulfonation with an additional 4% loading of sodium carbonate proving optimal. TEM indicated that sulfonation predominantly occurred within the secondary-cell-wall lignin, increasing cellulose accessibility to the cellulase enzymes.

Deep Eutectic Solvent Pretreatment of Transgenic Biomass With Increased CC Lignin Monomers.

The complex and heterogeneous polyphenolic structure of lignin confers recalcitrance to plant cell walls and challenges biomass processing for agroindustrial applications. Recently, significant efforts have been made to alter lignin composition to overcome its inherent intractability. In this work, to overcome technical difficulties related to biomass recalcitrance, we report an integrated strategy combining biomass genetic engineering with a pretreatment using a bio-derived deep eutectic solvent (DES).

The influence of lignin on the effectiveness of using a chemithermomechanical pulping based process to pretreat softwood chips and pellets prior to enzymatic hydrolysis.

Over the last century the pulp and paper sector has assessed various technologies to fractionate woody biomass to produce strong, bright fibers. Several of these processes have also been assessed for their potential to pretreat and fractionate biomass to enhance the subsequent enzymatic hydrolysis of the cellulosic component. Although many of these pretreatments are effective on agricultural residues, softwoods have proven more recalcitrant, primarily due to their high lignin content and structure.

The influence of lignin migration and relocation during steam pretreatment on the enzymatic hydrolysis of softwood and corn stover biomass substrates.

To be effective, steam pretreatment is typically carried out at temperatures/pressures above the glass transition point (Tg) of biomass lignin so that it can partly fluidize and relocate. The relocation of Douglas-fir and corn stover derived lignin was compared with the expectation that, with the corn stover lignin's lower hydrophobicity and molecular weight, it would be more readily fluidized. It was apparent that the Tg of lignin decreased as the moisture increased, with the easier access of steam to the corn stover lignin promoting its plasticization.