Increasing Lignin Concentration Research Articles

The balance between alleviating copper damage and maintaining root function during root pruning with excessive copper.

Coating high concentrations of copper (Cu) on the inner wall of containers can efficiently inhibit root entanglement of container-grown seedlings. However, how the protective and defensive responses of roots maintain root structure and function during Cu-root pruning is still unclear. Here, Duranta erecta seedlings were planted in the containers coated with 40 (T1), 80 (T2), 100 (T3), 120 (T4), 140 (T5), and 160 (T6) g L-1 Cu(OH)2 with containers without Cu(OH)2 as the control. Although T5 and T6 produced the best inhibitory effect on root entanglement, root anatomy structure was damaged. T1 and T2 not only failed to completely control root circling, but also led to decreased root activity and stunted growth. Cu(OH)2 treatments significantly increased lignin concentration of roots with the highest values at T3 and T4. Compared with T3, seedlings at T4 had higher height, biomass, and root activity and no significant root entanglement. Excessive Cu accumulation in Cu(OH)2 treatments changed the absorption of other mineral nutrients and their allocation in the roots, stems, and leaves. Overall, Ca was decreased while Mg, Mn, Fe, and K were increased, especially K and Mn at T4 which is related to defense capacity. The results indicate that there is a Cu threshold to balance root entanglement control, defense capacity, and nutrient uptake function under excessive Cu for container-grown D. erecta seedlings.

Bio‐Based Foams to Function as Future Plastic Substitutes by Biomimicry: Inducing Hydrophobicity with Lignin

To replace common plastics, bio‐based alternatives are needed. Cellulose foams, as plant‐based materials, are the most attractive solution, being often biodegradable and inexpensive and having the potential for distributed production. Cellulose and its derivatives, as raw materials, present a fundamental challenge, as they are hydrophilic. Herein, this problem is solved by drawing inspiration from the hydrophobic barrier that lignin creates in wood and applying lignin to methylcellulose (MC) foams. The lignin (0.0–1.0 wt% being the range studied here) is applied directly to the suspension consisting of water and MC (1.8 wt%), which is then foamed and solidified to a dry 3D porous structure. By comparing different types of lignin and the resulting surface morphologies, it is shown that organosolv lignin (OL) most strongly self‐assembles to the air–foam interfaces, achieving area fractions up to 27%. Using different concentrations of OL, how hydrophobicity—described by the initial water contact angle and its time evolution—increases with increasing lignin concentration is then shown. Thus, significantly increased water resistance (up to 91 times higher compared to the pure MC foam), a crucial property for developing novel bio‐based materials that can compete with traditional plastics, is able to be achieved.

SlSWEET11b mediates sugar reallocation to regulate tomato stem morphogenesis

The regulation mechanism of stem development has been classified in both Arabidopsis and woody species. However, studies on the regulation of stem development in tomatoes are limited. SlSWEET11b, a plasma membrane-located sugar transporter with the ability to shuttle sucrose and hexose, is expressed in the stem, leaves, flower, and fruit. It showed stable high expression levels during tomato stem development. Overexpression of SlSWEET11b caused alter in sugar transport and accumulation in stem, together with the increase in stem diameter, xylem width and the xylem cell layers. Nonetheless, stem diameter and xylem width decreased when loss of SlSWEET11b. SlSWEET11b overexpression led to increased lignin concentration in the stems. Our results suggest that SlSWEET11b might mediate sugar relocation and regulate lignin biosynthesis during stem development, thereby affecting fruit yield and quality.

The Effect of the Kraft Pulping Process, Wood Species, and pH on Lignin Recovery from Black Liquor

Lignin has shown a great potential to produce fuels, value-added chemicals, and functional materials due to its high-energy density and intrinsic aromatic-based structure. Yet, the lignin precipitation of different biomasses needs investigation because most of the work has been performed on softwood and much less is known about hardwoods. In fact, the lignin from these two wooden biomasses vary in composition and pulping performance, which can reflect on lignin precipitation. Therefore, the present study investigated the precipitation and composition of 40 distinct kraft lignins obtained from pine, acacia, sweetgum, and eucalyptus black liquors. Two lignin fractions were precipitated at different pHs, according to known industrial lignin separation practices (pH = 9.5 and 2.5) from black liquors taken at different levels of pulping. Overall, lignin recovery increased with increasing lignin concentration in the black liquor, i.e., higher amounts of lignin were obtained at higher levels of delignification. In addition, pine lignins showed superior yields than the hardwoods and were around five times purer. Among the hardwoods, lignin recovery increased with the S–G ratio of the native lignin, and eucalyptus showed the best performance by achieving the highest yields and purities. Finally, the present work compared the lignin recovery yield and the purity of softwood and different hardwood lignins in a systematic way, which will increase awareness of this underutilized green material and could potentially increase the interest in establishing new lignin plants across the globe.

Transcriptome analysis reveals candidate genes for dietary fiber metabolism in Rosa roxburghii fruit grown under different light intensities

The fruit of the perennial rosebush Rosa roxburghii were valued for their high levels of ascorbic acid, superoxide dismutase activity, and cancer preventing effects. The high cellulose and low pectin content of Rosa roxburghii fruit results in an undesirable fibrous texture and hence needs to be addressed. However, little is known about the molecular mechanisms underlying dietary fiber metabolism in this fruit. Here, we report that the contents of cellulose, pectin, and lignin were increased by shading treatments at the maturation stage of fruit development. Under 50% shading, the soluble pectin content increased by 16.39%, which may improve the fruit palatability. However, deeper shading of 100% caused the lignin content to increase by 28.86%, which conversely may lower fruit quality. Based on transcriptome analysis, we identified candidate genes involved in dietary fiber metabolism, including cellulose synthase (CesA) 1, 2, 3, and 5, â-1,4-xylosyltransferase (IRX), arabinosyltransferase (ARAD) 1 and 2, galacturonosyltransferase (GAUT), cellulolytic enzyme (Cx), and pectin methylesterase, in which CesA1, CesA2, CesA3, IRX, ARAD2, and GAUT3 significantly responded to shading and positively correlated with the content of their corresponding component. Furthermore, cinnamyl alcohol dehydrogenase was significantly regulated by shading treatment and positively correlated with increasing lignin concentration. These results may facilitate a better understanding of the molecular mechanisms of dietary fiber metabolism in R. roxburghii fruit under low light conditions and provide a framework for future crop improvement.

Laser induction of graphene onto lignin-upgraded flexible polymer matrix

Laser-induced graphene (LIG) has been demonstrated for various applications on a variety of rigid and flexible substrates such as wood, polyimide films and DVD disks. Here we report LIG produced from polydimethylsiloxane (PDMS) using a commercially available scribing laser. Marginal addition of lignin into PDMS enables the formation of LIG from this lignin upgraded PDMS film while preserving its stretchable nature. Increasing lignin concentration in PDMS matrix leads to better multi-layered LIG. Lower laser trace speeds also result in higher quality porous LIG structures. To demonstrate the application for flexible electronics, the LIG was deployed as a pressure sensor.

Corrosion inhibition using lignin of sugarcane bagasse

The quality of ferrous metals may decrease due to corrosion. The corrosion rate can be inhibited using inhibitors derived from organic compounds. Sugar cane waste from the sugar industry contains lignin that can be used as an environmentally friendly organic inhibitor, also called green inhibitor or eco-friendly inhibitor. The present article describes the use of green eco-friendly lignin natural polymer as corrosion inhibitor on the surface of ferrous metal in acidic media. Lignin was isolated from bagasse by acidification methods and characterized by FTIR to confirm the functional groups. The inhibition effectiveness of lignin against corrosion rate was observed by varying the concentration of lignin and metal immersion time in acidic medium. By using weight-loss method, it was found that the optimum inhibition effectiveness was 80.79% using the lignin concentration of 10 g/L and metal immersion time for 6 hours. The corrosion rate decreases with increasing lignin concentration of bagasse and length of immersion time.

Elevated CO2 concentration affected pine and oak litter chemistry and the respiration and microbial biomass of soils amended with these litters

Elevated atmospheric CO2 concentration ([CO2]) may change litter chemistry which affects litter decomposability. This study investigated respiration and microbial biomass of soils amended with litter of Pinus densiflora (a coniferous species; pine) and Quercus variabilis (a deciduous species; oak) that were grown under different atmospheric [CO2] and thus had different chemistry. Elevated [CO2] increased lignin/N through increased lignin concentration and decreased N concentration. The CO2 emission from the soils amended with litter produced under the same [CO2] regime was greater for oak than pine litter, confirming that broadleaf litter with lower lignin decomposes faster than needle leaf litter. Within each species, however, soils amended with high lignin/N litter grown under elevated [CO2] emitted more CO2 than those with low lignin/N litter grown under ambient [CO2]. Such contrasting effects of lignin/N on inter- and intra-species variations in litter decomposition should be ascribed to the effects of other litter chemistry variables including nonstructural carbohydrate, calcium and manganese as well as inhibitory effect of N on lignin decomposition. The microbial biomass was also higher in the soils amended with high lignin/N litter than those with low lignin/N litter probably due to low substrate use efficiency of lignin by microbes. Our study suggests that elevated [CO2] increases lignin/N for both species, but increased lignin/N does not always reduce soil respiration and microbial biomass. Further study investigating a variety of tree species is required for more comprehensive understanding of inter- and intra-species variations of litter decomposition under elevated [CO2].

Degradation changes in plant root cell wall structural molecules during extended decomposition of important agricultural crop and forage species

Little is known regarding changes in cell wall structural molecules (lignin, cellulose and hemicellulose) as plant roots decompose, despite their importance for soil organic matter (OM) formation. The objectives of this study were to quantify changes in root composition during 270 d incubations of ten important grain and forage crops utilizing forage fiber analysis and to characterize the changes in cell wall composition and structure using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Large, species-dependent variation was observed in the extent of root tissue decomposition over time, ranging from 82.5% of initial mass for alfalfa to 21.5% for switchgrass. Fiber analysis revealed that initial rapid decomposition increased lignin concentration and cellulose concentration while hemicellulose declined, whereas all three moieties degraded proportionally thereafter. Similar trends were found in the ratios between the DRIFTS diagnostic peaks for lignin, cellulose and the carbonyls of hemicellulose and wax components. Spectra illustrated changes during decomposition, particularly in more extensively decomposed roots. Features potentially indicative of suberin preservation were found in the region between 2800 cm−1 and 3000 cm−1. Examination of the region between 1000 cm−1 and 1300 cm−1 revealed possible change in hemicellulose structure. The results illustrate the effect of differences in cell wall composition and structure during root decomposition and expand understanding of the role of roots in soil OM dynamics. Variability in root degradation and change in cell wall composition among species demonstrate that characterization of a broad range of individual species is necessary to predict root contributions to soil C.

Polyurethane foam impregnated with lignin as a filler for the removal of crude oil from contaminated water

The present study describes the influence of the concentration of lignin when used as a filler in polyurethane foam for crude oil sorption. The foams (lignin 0–20wt%) were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis, contact angle and density. The FTIR analysis confirmed urethane linkage formation, showing that the chemical structure of the polymer was preserved, despite the addition of different lignin concentrations. Thermogravimetric analysis showed that the presence of lignin has altered the onset temperature (Tonset) of the foams, decreasing as the concentration of lignin is increased. The contact angle analysis showed a decrease in the hydrophobicity of the foams with increasing lignin concentration. All modified foams showed an improvement in the oil sorption capacity in a PUF/oil/water system, and the PUF-10 showed an improvement of about 35.5% compared to the PUF-blank. The Langmuir isotherm showed a better fit to the data and predicted a maximum oil adsorption of 28.9gg−1 by the PUF-10. The ΔG° value of −4.4kJmol−1 indicated that crude oil adsorption process by PUF-10 was spontaneous. The results of reuse of the PUF-10 showed that oil removal efficiency remained greater than 95% after five consecutive cycles.

A facile method for processing lignin reinforced chitosan biopolymer microfibres: optimising the fibre mechanical properties through lignin type and concentration

A chitosan biopolymer microfibre—reinforced by lignin—has been processed by a wet-spinning method. To optimise the fibre mechanical and structural properties two types of lignin, with molecular weights 28 000 g mol−1 and 60 000 g mol−1, were examined and the chitosan fibre was blended with the respective lignin type at 1, 3, 5, 7 and 8 wt% lignin concentrations. The main effects of lignin type and concentration, as well as the interaction between the two parameters, on the fibre tensile stiffness, extensibility, strength and toughness were evaluated using the two-factor analysis of variance. Significant variations in the respective mechanical properties were observed with varying lignin concentrations (P < 0.05). The magnitude of the respective mechanical properties is low at 1 wt% but peaks at 3 wt% before decreasing steadily with increasing lignin concentration. Except for extensibility, significant variations in the strength and toughness were observed with respect to lignin type (P < 0.05); variations in the stiffness were masked by interactions between lignin type and concentration. These results were related to the dispersion of lignin in the fibre and the nature of the bonds between lignin and chitosan, based on findings from scanning electron microscopy and Fourier transform infrared spectroscopy. This new method for the fabrication of chitosan biopolymer microfibre is inexpensive and versatile and could lend itself to the production of high performance biocomposite structures.

Overexpression of SbMyb60 impacts phenylpropanoid biosynthesis and alters secondary cell wall composition in Sorghum bicolor.

The phenylpropanoid biosynthetic pathway that generates lignin subunits represents a significant target for altering the abundance and composition of lignin. The global regulators of phenylpropanoid metabolism may include MYB transcription factors, whose expression levels have been correlated with changes in secondary cell wall composition and the levels of several other aromatic compounds, including anthocyanins and flavonoids. While transcription factors correlated with downregulation of the phenylpropanoid biosynthesis pathway have been identified in several grass species, few transcription factors linked to activation of this pathway have been identified in C4 grasses, some of which are being developed as dedicated bioenergy feedstocks. In this study we investigated the role of SbMyb60 in lignin biosynthesis in sorghum (Sorghum bicolor), which is a drought-tolerant, high-yielding biomass crop. Ectopic expression of this transcription factor in sorghum was associated with higher expression levels of genes involved in monolignol biosynthesis, and led to higher abundances of syringyl lignin, significant compositional changes to the lignin polymer and increased lignin concentration in biomass. Moreover, transgenic plants constitutively overexpressing SbMyb60 also displayed ectopic lignification in leaf midribs and elevated concentrations of soluble phenolic compounds in biomass. Results indicate that overexpression of SbMyb60 is associated with activation of monolignol biosynthesis in sorghum. SbMyb60 represents a target for modification of plant cell wall composition, with the potential to improve biomass for renewable uses.

The influence of temperature on the inhibition of carbon steel corrosion in acidic lignin

Purpose– This paper aims to investigate the influence of temperature and lignin concentration on the inhibition of carbon steel corrosion in 1 M HCl.Design/methodology/approach– Weight loss corrosion tests were performed at different temperatures in the range of 30-70°C (303-343 K).Findings– It was found that the corrosion inhibition efficiency (IE) of lignin on the carbon steel decreased when the temperature was increased from 60 to 70°C. However, at lower temperatures ranging from 30 to 50°C, the IE improved, due to occurrence of lignin adsorption on the surface of metal specimens. The IE was higher with increasing lignin concentration, thus reducing the weight loss of the carbon steel. The adsorption phenomenon involved exothermic processes because the value of enthalpy of adsorption (ΔH°ads) &lt; 0 and Gibbs free energy of adsorption (ΔG°ads) were less negative with increase in temperature. The entropy of adsorption (ΔS°ads) had negative values, representing the decrease in disorder of adsorption. The adsorption of lignin on the carbon steel surface in 1 M HCl was comprehensive, as deduced from kinetic and thermodynamic parameters. However, physisorption was the major contributor in the inhibition mechanism. The inhibitive features of carbon steel surfaces showed less damage once the steel was treated in lignin, as evident from macroscopy images.Practical implications– The use of lignin as an acid corrosion inhibitor at high temperature is practical in metal surface treatment process.Social implications– The use of organic compounds gives an advantage to the environment, universal health and save cost, as the compounds can be found in nature.Originality/value– Lignin can act as a flexible corrosion inhibitor within the temperature range of 30-70°C in 1 M HCl because it exhibits comprehensive adsorption (i.e. a combination of both physisorption and chemisorption) at specific concentrations.

Polyamide‐6 composites reinforced with cellulose fibers and fabricated by extrusion: Effect of fiber bleaching on mechanical properties and stability

We prepared polyamide‐6 (PA‐6) composites using bleached and semibleached cellulose fibers from Eucalyptus species by processing in a corotating interpenetrating twin‐screw extruder. PA‐6 is a challenging matrix because of its high processing temperature, which overlaps the thermodegradation temperature of the fibers. The selection of the processing conditions for extrusion and the use of the lubricant ethylene bis (stearamide) permitted the production of composites with 20, 30, and 40 wt% of bleached fibers, which are lighter than the corresponding glass fiber composites. Composites with 30 wt% of bleached fibers yield the best mechanical properties and good fiber/matrix interaction, as demonstrated by mechanical tests and scanning electron microscopy. X‐ray photoelectron spectroscopy studies showed that the natural moisture in the fibers promotes the fiber/matrix interaction through the formation of ester bonds. We assessed the effect caused by the presence of lignin in the fibers. Composites containing 30 wt% of semibleached fibers maintained the flexural properties and showed small improvements in thermal stability when compared with bleached fiber composites; however, there is a slight decrease in the tensile properties. Through accelerated aging tests, we observed that increased lignin concentration in the fibers reduced the formation of carbonyl compounds on sample surfaces, indicating a stabilization effect. POLYM. COMPOS., 38:299–308, 2017. © 2015 Society of Plastics Engineers

Interacting microbe and litter quality controls on litter decomposition: a modeling analysis.

The decomposition of plant litter in soil is a dynamic process during which substrate chemistry and microbial controls interact. We more clearly quantify these controls with a revised version of the Guild-based Decomposition Model (GDM) in which we used a reverse Michaelis-Menten approach to simulate short-term (112 days) decomposition of roots from four genotypes of Zea mays that differed primarily in lignin chemistry. A co-metabolic relationship between the degradation of lignin and holocellulose (cellulose+hemicellulose) fractions of litter showed that the reduction in decay rate with increasing lignin concentration (LCI) was related to the level of arabinan substitutions in arabinoxylan chains (i.e., arabinan to xylan or A∶X ratio) and the extent to which hemicellulose chains are cross-linked with lignin in plant cell walls. This pattern was consistent between genotypes and during progressive decomposition within each genotype. Moreover, decay rates were controlled by these cross-linkages from the start of decomposition. We also discovered it necessary to divide the Van Soest soluble (labile) fraction of litter C into two pools: one that rapidly decomposed and a second that was more persistent. Simulated microbial production was consistent with recent studies suggesting that more rapidly decomposing materials can generate greater amounts of potentially recalcitrant microbial products despite the rapid loss of litter mass. Sensitivity analyses failed to identify any model parameter that consistently explained a large proportion of model variation, suggesting that feedback controls between litter quality and microbial activity in the reverse Michaelis-Menten approach resulted in stable model behavior. Model extrapolations to an independent set of data, derived from the decomposition of 12 different genotypes of maize roots, averaged within <3% of observed respiration rates and total CO2 efflux over 112 days.

Enzymatic synthesis of lignin–siloxane hybrid functional polymers

This study combines the properties of siloxanes and lignin polymers to produce hybrid functional polymers that can be used as adhesives, coating materials, and/or multifunctionalized thin-coating films. Lignin-silica hybrid copolymers were synthesized by using a sol-gel process. Laccases from Trametes hirsuta were used to oxidize lignosulphonates to enhance their reactivity towards siloxanes and then were incorporated into siloxane precursors undergoing a sol-gel process. In vitro copolymerization studies using pure lignin monomers with aminosilanes or ethoxytrimethylsilane and analysis by ²⁹Si NMR spectroscopy revealed hybrid products. Except for kraft lignin, an increase in lignin concentration positively affected the tensile strength in all samples. Similarly, the viscosity generally increased in all samples with increasing lignin concentration and also affected the curing time.

Electrospinning of Technical Lignins for the Production of Fibrous Networks

Electrospinning is an effective strategy to produce micron and sub-micron diameter fibrous networks from a variety of polymeric systems. Using seven different technical lignins the effect of lignin structure on fiber formation by electrospinning was studied. Surprisingly, none of the technical lignins could be electrospun into continuous fibers, although beaded fiber formation was observed for the softwood Kraft lignin system at high concentration (>50 wt%). However, the addition of poly(ethylene oxide) dramatically affected the electrospinning behavior and fiber formation. For all of the technical lignins a clear transition from electrospray or beaded fibers to uniform fibers was observed upon addition of poly(ethylene oxide); the lignin concentration dependent on poly(ethylene oxide) content. In all of the systems a linear increase in fiber diameter with increasing lignin concentration was observed. At the same concentration, the various lignin solutions had varying viscosities and different electrospinning behavior, that is, fiber diameter and ability to form uniform fibers, suggesting lignin specific structures and intermolecular interactions are influencing solution properties and electrospinning behavior. In fact, specific viscosity versus concentration plots reveal scaling exponents’, η ∼ c7.4–7.8 consistent with a branched polymer participating in intermolecular interactions such as hydrogen bonding or association complexes.

Dual role of lignin in plant litter decomposition in terrestrial ecosystems

Plant litter decomposition is a critical step in the formation of soil organic matter, the mineralization of organic nutrients, and the carbon balance in terrestrial ecosystems. Biotic decomposition in mesic ecosystems is generally negatively correlated with the concentration of lignin, a group of complex aromatic polymers present in plant cell walls that is recalcitrant to enzymatic degradation and serves as a structural barrier impeding microbial access to labile carbon compounds. Although photochemical mineralization of carbon has recently been shown to be important in semiarid ecosystems, litter chemistry controls on photodegradative losses are not understood. We evaluated the importance of litter chemistry on photodegradation of grass litter and cellulose substrates with varying levels of lignin [cellulose-lignin (CL) substrates] under field conditions. Using wavelength-specific light attenuation filters, we found that light-driven mass loss was promoted by both UV and visible radiation. The spectral dependence of photodegradation correlated with the absorption spectrum of lignin but not of cellulose. Field incubations demonstrated that increasing lignin concentration reduced biotic decomposition, as expected, but linearly increased photodegradation. In addition, lignin content in CL substrates consistently decreased in photodegradative incubations. We conclude that lignin has a dual role affecting litter decomposition, depending on the dominant driver (biotic or abiotic) controlling carbon turnover. Under photodegradative conditions, lignin is preferentially degraded because it acts as an effective light-absorbing compound over a wide range of wavelengths. This mechanistic understanding of the role of lignin in plant litter decomposition will allow for more accurate predictions of carbon dynamics in terrestrial ecosystems.

Growth, wood chemistry, and fibre length of Norway spruce in a long-term nutrient optimization experiment

The study was performed as part of a nutrient optimization experiment at Asa in southern Sweden. The experiment was established 1987, in a Norway spruce ( Picea abies (L.) Karst.) stand planted in 1975. In the nutrient optimization treatment (IL), all essential macro- and micronutrients were supplied, with irrigation water, every second day during the growing season. In October 2003, nine trees were harvested on both untreated control and IL plots. The IL treatment increased annual ring width during the first years of the experiment by ca. 30% and cumulative cross-sectional area 1.5-fold by the end of the experiment. Tracheid length was, however, not affected by the IL treatment. The nitrogen concentration of wood increased and starch concentration decreased as an effect of the IL treatment, suggesting that carbon was allocated to growth rather than storage. The IL treatment increased lignin concentration of wood by 3.4%. Chemical composition varied at different heights along the stem, but with no apparent trend.

Non-isothermal Crystallization Behavior of Lignin-Filled Polyethylene Terepthalate (PET)

The important role of lignin can be understood from the interesting properties of the natural composite, wood. Lignin, which has a cross-linked phenyl propane skeleton containing some active sites as well as an aromatic stable structure having a potential of providing dynamic compatibility with polyethylene terepthalate (PET), is a low-cost chemical constituent material available in large quantities as a waste from pulp and paper industries. On account of these properties as well as biodegradability, conventional inert filler materials such as mica or metal oxides may be replaced by alkali lignin to produce a material with better thermal characteristics, exploring a new way of utilizing lignin. These objectives have been studied through the non-isothermal crystallization behavior of purified alkali lignin-filled PET blends with varying compositions. Analysis by DSC and TGA showed the modification in a nucleation process, the steady acceleration of the crystallization process with increasing lignin proportion. Besides significant decrease in the glass transition temperature, decreasing melting temperature with increasing lignin concentration should account for the processibility of PET at lower temperature.