Combination of Analytical Pyrolysis and fractionation of technical lignin as a tool for improvement of its antioxidant properties

Antioxidant properties of parent lignin and its fractions was assessed in the tests with free radicals ABTS•+ and DPPH. Increasing ratio between content of syringyl and guaiacyl substructures and the extent of conjugation of lignin macromolecule (Py-GC/MS data) enhanced lignin radical scavenging capacity. The compositional heterogeneity (the presence of lipophillic extractives) had negative impact on the lignin radical scavenging capaci

Study on single calibration of near infrared reflectance spectroscopy for lignin

The study of single calibration of near infrared reflectance srectroscory for lignin was done using 50 feed samples and its paired 50 fecal samrles from dairy cows. These samrles were collected from digestion trials. in which the in vivo digestibility values were deternlined, The dlgC-ostibillty of these feed samples were separated into two grours, namely Italian ryegruss only (n= 19) and combinution of Italian ryegrass and concentmte (n=31), The NIRS srectm or these samrles were recorded using I'aciflc Scientific (Neotec) model 6500 (Perstorp Analytical, Silver Srring, MD) instrument equirrl'Cl with lSI software (InfraSoft International, Port Matilda, PAl for analysIs, Three arproach methods for devcloring the single calibmtion were, (I) Lignin in feed and feces was detcn;1ined usmg lignin calibratIOn developed from Italian ryegrass (L1RG): (2) Lignin of ft.'Cd and feces was detennined lIsing lignin calibmtion developed ITom feces (LFEC): and (3) Lignin oC feed and feces were detemlined using the caiibmtion equation for lignin develorcd from Si.U11rles of fecdstufl's wld feces (LMIX). The resulb showed that lignin of feed and feces in il~ function for digestibility marker could be detennincd by single calibration developed from samrles consisting of Italian ryegm~s, concentrates and feces

Flammability and Thermal Properties of Rigid Polyurethane Foams Containing Wheat Straw Lignin

Due to development of new generation of biomass processing, the examination of novel lignin products for creation of lignin-containing PU remains actual up to now. For preparation of lignin containing PU in this study a novel BIOLIGNIN was used. BIOLIGNIN is extracted from wheat straw in organic acid media using biomass refinery technology. The influence of chemically non-modified BIOLIGNIN and oxypropylated BIOLIGNIN on flammability and thermal properties in rigid PU foams was studied. Improvement of flame resistance and thermal stability is observed if chemically non-modified lignin as well as oxypropylated lignin is used

Improved Lignin Polyurethane Properties with Lewis Acid Treatment

Chemical modification strategies to improve the mechanical properties of lignin-based polyurethanes are presented. We hypothesized that treatment of lignin with Lewis acids would increase the concentration of hydroxyl groups available to react with diisocyanate monomers. Under the conditions used, hydrogen bromide-catalyzed modification resulted in a 28% increase in hydroxyl group content. Associated increases in hydrophilicity of solvent-cast thin films were also recorded as evidenced by decreases in water contact angle. Polyurethanes were then prepared by first preparing a prepolymer based on mixtures of toluene-2,4-diisocyanate (TDI) and unmodified or modified lignin, then polymerization was completed through addition of polyethylene glycol (PEG), resulting in mass ratios of TDI:lignin:PEG of 43:17:40 in the compositions investigated here. The mixture of TDI and unmodified lignin resulted in a lignin powder at the bottom of the liquid, suggesting it did not react directly with TDI. However, a homogeneous solution resulted when TDI and the hydrogen bromide-treated lignin were mixed, suggesting demethylation indeed increased reactivity and resulted in better integration of lignin into the urethane network. Significant improvements in mechanical properties of modified lignin polyurethanes were observed, with a 6.5-fold increase in modulus, which were attributed to better integration of the modified lignin into the covalent polymer network due to the higher concentration of hydroxyl groups. This research indicates that chemical modification strategies can lead to significant improvements in the properties of lignin-based polymeric materials using a higher fraction of an inexpensive lignin monomer from renewable resources and a lower fraction an expensive, petroleum-derived isocyanate monomer to achieve the required material properties

Silencing CHALCONE SYNTHASE in maize impedes the incorporation of tricin into lignin and increases lignin content

Lignin is a phenolic heteropolymer that is deposited in secondary-thickened cell walls, where it provides mechanical strength. A recent structural characterization of cell walls from monocot species showed that the flavone tricin is part of the native lignin polymer, where it is hypothesized to initiate lignin chains. In this study, we investigated the consequences of altered tricin levels on lignin structure and cell wall recalcitrance by phenolic profiling, nuclear magnetic resonance, and saccharification assays of the naturally silenced maize (Zea mays) C2-Idf (inhibitor diffuse) mutant, defective in the CHALCONE SYNTHASE Colorless2 (C2) gene. We show that the C2-Idf mutant produces highly reduced levels of apigenin-and tricin-related flavonoids, resulting in a strongly reduced incorporation of tricin into the lignin polymer. Moreover, the lignin was enriched in beta-beta and beta-5 units, lending support to the contention that tricin acts to initiate lignin chains and that, in the absence of tricin, more monolignol dimerization reactions occur. In addition, the C2-Idf mutation resulted in strikingly higher Klason lignin levels in the leaves. As a consequence, the leaves of C2-Idf mutants had significantly reduced saccharification efficiencies compared with those of control plants. These findings are instructive for lignin engineering strategies to improve biomass processing and biochemical production

Expression of a bacterial 3-dehydroshikimate dehydratase reduces lignin content and improves biomass saccharification efficiency.

Lignin confers recalcitrance to plant biomass used as feedstocks in agro-processing industries or as source of renewable sugars for the production of bioproducts. The metabolic steps for the synthesis of lignin building blocks belong to the shikimate and phenylpropanoid pathways. Genetic engineering efforts to reduce lignin content typically employ gene knockout or gene silencing techniques to constitutively repress one of these metabolic pathways. Recently, new strategies have emerged offering better spatiotemporal control of lignin deposition, including the expression of enzymes that interfere with the normal process for cell wall lignification. In this study, we report that expression of a 3-dehydroshikimate dehydratase (QsuB from Corynebacterium glutamicum) reduces lignin deposition in Arabidopsis cell walls. QsuB was targeted to the plastids to convert 3-dehydroshikimate - an intermediate of the shikimate pathway - into protocatechuate. Compared to wild-type plants, lines expressing QsuB contain higher amounts of protocatechuate, p-coumarate, p-coumaraldehyde and p-coumaryl alcohol, and lower amounts of coniferaldehyde, coniferyl alcohol, sinapaldehyde and sinapyl alcohol. 2D-NMR spectroscopy and pyrolysis-gas chromatography/mass spectrometry (pyro-GC/MS) reveal an increase of p-hydroxyphenyl units and a reduction of guaiacyl units in the lignin of QsuB lines. Size-exclusion chromatography indicates a lower degree of lignin polymerization in the transgenic lines. Therefore, our data show that the expression of QsuB primarily affects the lignin biosynthetic pathway. Finally, biomass from these lines exhibits more than a twofold improvement in saccharification efficiency. We conclude that the expression of QsuB in plants, in combination with specific promoters, is a promising gain-of-function strategy for spatiotemporal reduction of lignin in plant biomass

Analysis of gas chromatography/mass spectrometry data for catalytic lignin depolymerization using positive matrix factorization

Various catalytic technologies are being developed to efficiently convert lignin into renewable chemicals. However, due to its complexity, catalytic lignin depolymerization often generates a wide and complex distribution of product compounds. Gas chromatography/mass spectrometry (GC-MS) is a common analytical technique to profile the compounds that comprise lignin depolymerization products. GC-MS is applied not only to determine the product composition, but also to develop an understanding of the catalytic reaction pathways and of the relationships among catalyst structure, reaction conditions, and the resulting compounds generated. Although a very useful tool, the analysis of lignin depolymerization products with GC-MS is limited by the quality and scope of the available mass spectral libraries and the ability to correlate changes in GC-MS chromatograms to changes in lignin structure, catalyst structure, and other reaction conditions. In this study, the GC-MS data of the depolymerization products generated from organosolv hybrid poplar lignin using a copper-doped porous metal oxide catalyst and a methanol/dimethyl carbonate co-solvent was analyzed by applying a factor analysis technique, positive matrix factorization (PMF). Several different solutions for the PMF model were explored. A 13-factor solution sufficiently explains the chemical changes occurring to lignin depolymerization products as a function of lignin, reaction time, catalyst, and solvent. Overall, seven factors were found to represent aromatic compounds, while one factor was defined by aliphatic compounds

Fractionation of CIMV wheat straw lignin as an approach for promoting it interaction with isocyanates and characteristic of products obtained

The reactivity of CIMV lignin fractions with MDI has been investigated in extra dry dioxane (DOX) in argon atmosphere at 25 degrees of Celsius, using FTIR spectroscopy (absorbance band at 2273 cm^-1) for monitoring the NCO group disappearance during reaction. Five CIMV lignin fractions were obtained and investigated: 2 fractions obtained by separate extractions with DOX and methanol and 3 fractions obtained in the process of sequential extraction of CIMV lignin with dichloromethane, methanol and methanol/dichloromethane mixture. The highest second rate constants was detected for both methanol soluble lignin fractions

Lignin engineering in forest trees

Wood is a renewable resource that is mainly composed of lignin and cell wall polysaccharides. The polysaccharide fraction is valuable as it can be converted into pulp and paper, or into fermentable sugars. On the other hand, the lignin fraction is increasingly being considered a valuable source of aromatic building blocks for the chemical industry. The presence of lignin in wood is one of the major recalcitrance factors in woody biomass processing, necessitating the need for harsh chemical treatments to degrade and extract it prior to the valorization of the cell wall polysaccharides, cellulose and hemicellulose. Over the past years, large research efforts have been devoted to engineering lignin amount and composition to reduce biomass recalcitrance toward chemical processing. We review the efforts made in forest trees, and compare results from greenhouse and field trials. Furthermore, we address the value and potential of CRISPR-based gene editing in lignin engineering and its integration in tree breeding programs

Anaerobic co-digestion of acetate-rich with lignin-rich wastewater and the effect of hydrotalcite addition

The methane potential and biodegradability of different ratios of acetate and lignin-rich effluents from a neutral sulfite semi-chemical (NSSC) pulp mill were investigated. Results showed ultimate methane yields up to 333 ± 5 mL CH4/gCOD when only acetate-rich substrate was added and subsequently lower methane potentials of 192 ± 4 mL CH4/gCOD when the lignin fraction was increased. The presence of lignin showed a linear decay in methane production, resulting in a 41% decrease in methane when the lignin-rich feed had a 30% increase. A negative linear correlation between lignin content and biodegradability was also observed. Furthermore, the effect of hydrotalcite (HT) addition was evaluated and showed increase in methane potential of up to 8%, a faster production rate and higher soluble lignin removal (7–12% higher). Chemical oxygen demand (COD) removal efficiencies between 64 and 83% were obtained for all samples.Peer ReviewedPostprint (author's final draft