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The catalytic oxidation of phenethoxybenzene as a lignin model compound with a β-O-4 bond was conducted using the Keggin-type polyoxometalate nanocatalyst (TBA)[sub.5][PMo[sub.10]V[sub.2]O[sub.40]]. The optimization of the process’s operational conditions was carried out using response surface methodology. The statistically significant variables in the process were determined using a fractional factorial design. Based on this selection, a central circumscribed composite experimental design was used to maximize the phenethoxybenzene conversion, varying temperature, reaction time, and catalyst load. The optimal conditions that maximized the phenethoxybenzene conversion were 137 °C, 3.5 h, and 200 mg of catalyst. In addition, under the optimized conditions, the Kraft lignin catalytic depolymerization was carried out to validate the effectiveness of the process. The depolymerization degree was assessed by gel permeation chromatography from which a significant decrease in the molar mass distribution Mw from 7.34 kDa to 1.97 kDa and a reduction in the polydispersity index PDI from 6 to 3 were observed. Furthermore, the successful cleavage of the β-O-4 bond in the Kraft lignin was verified by gas chromatography–mass spectrometry analysis of the reaction products. These results offer a sustainable alternative to efficiently converting lignin into valuable products.

Lignin, the term commonly used in literature, represents a group of heterogeneous aromatic compounds of plant origin. Protolignin or lignin in the cell wall is entirely different from the commercially available technical lignin due to changes during the delignification process. In this paper, we assess the status of lignin valorization in terms of commercial products. We start with existing knowledge of the lignin/protolignin structure in its native form and move to the technical lignin from various sources. Special attention is given to the patents and lignin-based commercial products. We observed that the technical lignin-based commercial products utilize coarse properties of the technical lignin in marketed formulations. Additionally, the general principles of polymers chemistry and self-assembly are difficult to apply in lignin-based nanotechnology, and lignin-centric investigations must be carried out. The alternate upcoming approach is to develop lignin-centric or lignin first bio-refineries for high-value applications; however, that brings its own technological challenges. The assessment of the gap between lab-scale applications and lignin-based commercial products delineates the challenges lignin nanoparticles-based technologies must meet to be a commercially viable alternative.

In the present study, the effects of macro- and microclimatic conditions, month of harvest, and leaf age at harvest on the bromatological composition and polyphenol content of Gymnopodium floribundum leaves were evaluated. Leaves were harvested in December 2017 and 2018 and March, June, and September 2018. At each harvest, three composite samples of mixed-age leaves were collected from 12 trees (four trees for each sample), and the sampling was repeated on day 90 post-harvest to collect 90-day-old leaves. Fresh and dry matter, crude protein, acid and neutral detergent fibers (ADF and NDF, respectively), lignin, total tannins, condensed tannins (CT), total phenols, in vitro dry matter (IVDMD) and organic matter (IVOMD) digestibility, and metabolizable energy (ME) were estimated. Rainfall, relative humidity, and microhumidity were associated with chemical composition. IVDMD, IVOMD, and ME were highest in leaves sampled in March regardless of age (p < 0.001). Water content, ADF, NDF, and lignin were highest in the leaves sampled in September, regardless of age (p < 0.05), suggesting that leaves require more structural support in the rainy season. CT content was highest in September in the mixed-age leaves and in September and December in the 90-day-old leaves (p < 0.05). A high fiber and CT content during the period of rapid leaf growth could deter herbivory.

Some agroforestry residues such as orange and olive tree pruning have been extensively evaluated for their valorization due to its high carbohydrates content. However, lignin-enriched residues generated during carbohydrates valorization are normally incinerated to produce energy. In order to find alternative high added-value applications for these lignins, a depth characterization of them is required. In this study, lignins isolated from the black liquors produced during soda/anthraquinone (soda/AQ) pulping of orange and olive tree pruning residues were analyzed by analytical standard methods and Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (solid state 13C NMR and 2D NMR) and size exclusion chromatography (SEC). Thermal analysis (thermogravimetric analysis (TGA), differential scanning calorimetry (DSC)) and antioxidant capacity (Trolox equivalent antioxidant capacity) were also evaluated. Both lignins showed a high OH phenolic content as consequence of a wide breakdown of β-aryl ether linkages. This extensive degradation yielded lignins with low molecular weights and polydispersity values. Moreover, both lignins exhibited an enrichment of syringyl units together with different native as well as soda/AQ lignin derived units. Based on these chemical properties, orange and olive lignins showed relatively high thermal stability and good antioxidant activities. These results make them potential additives to enhance the thermo-oxidation stability of synthetic polymers.

The ratio of syringyl (S) and guaiacyl (G) units in lignin has been regarded as a major factor in determining the maximum monomer yield from lignin depolymerization. This limit arises from the notion that G units are prone to C-C bond formation during lignin biosynthesis, resulting in less ether linkages that generate monomers. This study uses reductive catalytic fractionation (RCF) in flow-through reactors as an analytical tool to depolymerize lignin in poplar with naturally varying S/G ratios, and directly challenges the common conception that the S/G ratio predicts monomer yields. Rather, this work suggests that the plant controls C-O and C-C bond content by regulating monomer transport during lignin biosynthesis. Overall, our results indicate that additional factors beyond the monomeric composition of native lignin are important in developing a fundamental understanding of lignin biosynthesis. The ratio of syringyl (S) and guaiacyl (G) units in lignin has been regarded as a major factor in determining the maximum monomer yield. Here, the authors challenge this common conception using reductive catalytic fractionation in flow-through reactors as an analytical tool to depolymerize lignin in poplar with naturally varying S/G ratios.

Lignin is central to overcoming recalcitrance in the enzyme hydrolysis of lignocellulose. While the term implies a physical barrier in the cell wall structure, there are also important biochemical components that direct interactions between lignin and the hydrolytic enzymes that attack cellulose in plant cell walls. Progress toward a deeper understanding of the lignin synthesis pathway – and the consistency between a range of observations over the past 40 years in the very extensive literature on cellulose hydrolysis – is resulting in advances in reducing a major impediment to cellulose conversion: the cost of enzymes. This review addresses lignin and its role in the hydrolysis of hardwood and other lignocellulosic residues. Lignin and lignin-derived phenolic compounds inhibit lignocellulolytic enzymes. While lignin nonspecifically adsorbs enzymes, phenolic compounds inhibit and/or deactivate them. The effect will vary depending on type of phenolic compounds, their concentration, and possible synergistic effects. The effect will also depend on the type of enzyme and microorganism from which they were produced. Enzymes from Trichoderma reesei are more susceptible to the inhibitory and/or deactivating effects than those from Aspergillus niger. Noncatalytic proteins, such as bovine serum albumin or soy-derived proteins, minimize the nonspecific adsorption of the hydrolytic enzymes on lignin. Understanding these mechanisms of enzyme inhibition or deactivation and approaches to mitigate them potentially favor continued reduction of cellulose conversion-associated costs.

Tűzesetek során a fa mint építőanyag a legéghetőbb anyagok közé tartozik 300 o C körüli gyulladáspontjával. Tüzek létrejöttekor a lángterjedést minden esetben sugárzó hőterhelés előzi meg, amely eltérő mértékű károsodást okozhat a különböző faanyagokban, valamint hatására beindulhat a pirolízis is. Ezért kiemelt figyelmet kell fordítani a fák sugárzó hővel szembeni viselkedésének és az elleni védelem kutatásának is. Munkánkban olyan hazai természetes fafajok (erdei fenyő, lucfenyő, gyertyán, akác, bükk) viselkedését vizsgáltuk, amelyek épületszerkezeti anyagként és belsőépítészeti szerkezeti anyagként is megjelennek az építményekben. Tanulmányunkban azt vizsgáltuk, hogy a kereskedelemben kapható égéskésleltetőkkel kezelt faanyagok hogyan viselkednek sugárzó hőnek kitéve. A károsodás mértékét tömegveszteség mérésével adtuk meg. Emellett a minták mechanikai és felületi károsodása sem volt elhanyagolható. A faanyagokra rendszeresített és ismert Lindner-módszernél alkalmazott szabványos méréstől eltérően a sugárzó hőt biztosító berendezésünk egyedi gyártású, nem szabványos kialakítású berendezés volt.

Lignin, a structural component of lignocellulosic plants, is an alternative raw material with enormous potential to replace diminishing fossil-based resources for the sustainable production of many chemicals and materials. Unfortunately, lignin’s heterogeneity, low reactivity, and strong intra- and intermolecular hydrogen interactions and modifications introduced during the pulping process present significant technical challenges. However, the increasing ability to tailor lignin biosynthesis pathways by targeting enzymes and the continued discovery of more robust biocatalysts are enabling the synthesis of novel valuable products. This review summarizes how enzymes involved in lignin biosynthesis pathways and microbial enzymes are being harnessed to produce chemicals and materials and to upgrade lignin properties for the synthesis of a variety of value-added lignin industrial products. Lignin is a versatile alternative industrial raw material.The enzymes involved in lignin biosynthesis can be engineered to produce industrially relevant raw materials.The lignin transformation machinery in microorganisms can be exploited to produce a variety of industrially relevant raw materials.Enzymes increase lignin reactivity and miscibility with other polymers.Enzymes are useful biocatalysts for upgrading technical lignin properties for the production of functional materials.

Lignin is a chemically complex polymer that lends woody plants and trees their rigidity. Humans have traditionally either left it intact to lend rigidity to their own wooden constructs, or burned it to generate heat and sometimes power. With the advent of major biorefining operations to convert cellulosic biomass into ethanol and other liquid fuels, researchers are now exploring how to transform the associated leftover lignin into more diverse and valuable products. Ragauskas et al. ( 10.1126/science.1246843 ) review recent developments in this area, ranging from genetic engineering approaches that tune lignin properties at the source, to chemical processing techniques directed toward extracting lignin in the biorefinery and transforming it into high-performance plastics and a variety of bulk and fine chemicals. Research and development activities directed toward commercial production of cellulosic ethanol have created the opportunity to dramatically increase the transformation of lignin to value-added products. Here, we highlight recent advances in this lignin valorization effort. Discovery of genetic variants in native populations of bioenergy crops and direct manipulation of biosynthesis pathways have produced lignin feedstocks with favorable properties for recovery and downstream conversion. Advances in analytical chemistry and computational modeling detail the structure of the modified lignin and direct bioengineering strategies for future targeted properties. Refinement of biomass pretreatment technologies has further facilitated lignin recovery, and this coupled with genetic engineering will enable new uses for this biopolymer, including low-cost carbon fibers, engineered plastics and thermoplastic elastomers, polymeric foams, fungible fuels, and commodity chemicals.