Lignin Materials Research Articles

Developing fast enzyme recycling strategy through elucidating enzyme adsorption kinetics on alkali and acid pretreated corn stover

BackgroundAlthough various pre-treatment methods have been developed to disrupt the structure of lignocellulosic biomass, high dosage of cellulases is still required to hydrolyze lignocellulose to fermentable sugars. Enzyme recycling via recycling unhydrolyzed solids after enzymatic hydrolysis is a promising strategy to reduce enzyme loading for production of cellulosic ethanol.ResultsTo develop effective enzyme recycling method via recycling unhydrolyzed solids, this work investigated both enzymatic hydrolysis kinetics and enzyme adsorption kinetics on dilute acid and dilute alkali pre-treated corn stover (CS). It was found that most of the hydrolysable biomass was hydrolyzed in the first 24 h and about 40% and 55% of the enzymes were adsorbed on unhydrolyzed solids for dilute alkali-CS and dilute acid-CS, respectively, at 24 h of enzymatic hydrolysis. Lignin played a significant role in such adsorption and lignin materials derived from dilute acid-CS and dilute alkali-CS possessed different enzyme adsorption properties. Enzyme recycling was performed by recycling unhydrolyzed solids after 24 h enzymatic hydrolysis for five successive rounds, and successfully reduced 40% and 50% of the enzyme loadings for hydrolysis of dilute alkali-CS and for hydrolysis of dilute acid-CS, respectively.ConclusionsThis study presents that the enzymes adsorbed on the unhydrolyzed solids after short-time hydrolysis could be recycled effectively for efficient enzymatic hydrolysis. Lignin derived from dilute acid-CS has higher enzyme adsorption capacity than the lignin derived from dilute alkali-CS, which led to more enzymes recycled. By applying the enzyme recycling strategy developed in this study, the enzyme dosage needed for effective cellulose hydrolysis can be significantly reduced.

Lignin Degradation Efficiency of Chemical Pre-Treatments on Banana Rachis Destined to Bioethanol Production.

Valuable biomass conversion processes are highly dependent on the use of effective pretreatments for lignocellulose degradation and enzymes for saccharification. Among the nowadays available treatments, chemical delignification represents a promising alternative to physical-mechanical treatments. Banana is one of the most important fruit crops around the world. After harvesting, it generates large amounts of rachis, a lignocellulosic residue, that could be used for second generation ethanol production, via saccharification and fermentation. In the present study, eight chemical pretreatments for lignin degradation (organosolv based on organic solvents, sodium hypochlorite, hypochlorous acid, hydrogen peroxide, alkaline hydrogen peroxide, and some combinations thereof) have been tested on banana rachis and the effects evaluated in terms of lignin removal, material losses, and chemical composition of pretreated material. Pretreatment based on lignin oxidation have demonstrated to reach the highest delignification yield, also in terms of monosaccharides recovery. In fact, all the delignified samples were then saccharified with enzymes (cellulase and beta-glucosidase) and hydrolysis efficiency was evaluated in terms of final sugars recovery before fermentation. Analysis of Fourier transform infrared spectra (FTIR) has been carried out on treated samples, in order to better understand the structural effects of delignification on lignocellulose. Active chlorine oxidations, hypochlorous acid in particular, were the best effective for lignin removal obtaining in the meanwhile the most promising cellulose-to-glucose conversion.

Synthetic Bio-Graphene Based Nanomaterials through Different Iron Catalysts.

Kraft lignin was catalytically graphitized to graphene-based nanostructures at 1000 °C under argon atmosphere with four iron catalysts, iron(III) nitrate (Fe-N); iron(II) chloride (Fe-Cl2); iron(III) chloride (Fe-Cl3); and iron(II) sulfate (Fe-S). The catalytic decomposition process of iron-promoted lignin materials was examined using thermalgravimetric analysis and temperature-programmed decomposition methods. The crystal structure, morphology and surface area of produced materials were characterized by means of X-ray diffraction, Raman, scanning electron microscopy, high resolution transmission electron microscopy and N2 adsorption−desorption techniques. Experimental results indicated that iron nitrate catalyst had better iron dispersion three other iron salts. Iron nitrate was the most active catalyst among four iron salts. The low activity of iron in iron chloride-promoted samples was because the residual chlorine over iron surfaces prevent iron interaction with lignin functional groups.

Biodegradation of lignin by Pseudomonas sp. Q18 and the characterization of a novel bacterial DyP-type peroxidase.

Lignin valorization can be obtained through cleavage of selected bonds by microbial enzymes, in which lignin is segregated from cellulose and hemicellulose and abundant phenolic compounds can be provided. In this study, Pseudomonas sp. Q18, previously isolated from rotten wood in China, was used to degrade alkali lignin and raw lignocellulosic material. Gel-permeation chromatography, field-emission scanning electron microscope, and GC-MS were combined to investigate the degradation process. The GC-MS results revealed that the quantities of aromatic compounds with phenol ring from lignin increased significantly after incubation with Pseudomonas sp. Q18, which indicated the degradation of lignin. According to the lignin-derived metabolite analysis, it was proposed that a DyP-type peroxidase (PmDyP) might exist in strain Q18. Thereafter, the gene of PmDyP was cloned and expressed, after which the recombinant PmDyP was purified and the enzymatic kinetics of PmDyP were assayed. According to results, PmDyP showed promising characteristics for lignocellulosic biodegradation in biorefinery.

Humic substrates extracted by recycling factory tea waste improved soil properties and tea productivity: an innovative approach

Factory tea waste is a high lignin and phenolic compounds-containing fibrous material generated in tonnes in tea manufacturing factories. In spite of its high nitrogen content, these physical and chemical properties limit its application as an organic amendment in soil. In this study, a novel technique was developed for extracting humic substrates by recycling factory tea waste and potential of those extracted humic substrates for improving soil properties and tea productivity was evaluated under field condition. Humic substrates are organic soil amendment that is often used for enhancing chemical and biochemical properties in soil. For extracting humic substrates, factory tea waste was processed through multi-step technique combined with easily available plant biomass like aquatic weeds. The method was suitable for extracting up to 25–30 L humic substrate solution containing 25.1 ± 3.8 g L−1 active constituent, 507.3 ± 11.8 mg L−1 total nitrogen and 2.91 ± 0.07 g L−1 total potassium by recycling each kilogram factory tea waste. The extract had shown fair similarity with standard humic acids. Under field condition, extracted humic substrates lead up to 6% increase in tea productivity and improved soil chemical properties. The residue remained at the end of this process was further vermicomposted to prepare organic amendment having total nitrogen content 1.34 ± 0.07 mg g−1 with C/N ratio 10.87 ± 0.92. In this study, the addition of pond sediment produced inferior quality humic substrate and vermicompost.

Selective Cleavage of C-O Bonds in Lignin Catalyzed by Rhenium(VII) Oxide (Re2 O7 ).

Invited for this month's cover are the collaborating groups of Dr. Changzhi Li from Dalian Institute of Chemical Physics, China, and Dr. Lican Lu, Xiangtan University, China. The cover picture shows the harvest of a renewable supply of aromatic compounds accessible from lignin model compounds and lignin feedstocks through the selective Re2 O7 -catalyzed cleavage of lignin C-O bonds. This study paves the way towards the development of rhenium-based catalysts for the reductive valorization of realistic lignin materials in a controlled manner. Read the full text of the article at 10.1002/cplu.201700547.

Sustainability analysis of organic fraction of municipal solid waste conversion techniques for efficient resource recovery in India through case studies

Worldwide solid waste generation is nearly 1.3 billion tonnes/year, whereas in India 62 million tonnes of solid waste is generated per year by 377 million urban people. The increasing amount of solid waste in India, nearly 50% of which is organic matter, is the major concern for treatment and waste management. Several technologies are already in practice for the treatment of organic fraction of municipal solid waste (OFMSW) in India. It is important to assess the sustainability of these processes. In this study, the existing OFMSW technologies in India were examined. Case-study approach was taken for this purpose along with some published secondary reports. It was found that the selection of technology quite depends on the composition of the OFMSW. Food waste rich fractions are recommended for biomethanation, whereas the fractions rich in market waste and household waste are suitable for composting. Fractions rich in lignin and lignocellulosic materials are suitable for pyrolysis and gasification, whereas the rejects are to be sent for RDF preparation. Based on the findings, a sustainable framework has also been proposed, implementation of which may result in better waste management.

Carbon with Expanded and Well-Developed Graphene Planes Derived Directly from Condensed Lignin as a High-Performance Anode for Sodium-Ion Batteries.

In this study, we demonstrate that lignin, which constitutes 30-40 wt % of the terrestrial lignocellulosic biomass and is produced from second generation biofuel plants as a cheap byproduct, is an excellent precursor material for sodium-ion battery (NIB) anodes. Because it is rich in aromatic monomers that are highly cross-linked by ether and condensed bonds, the lignin material carbonized at 1300 °C (C-1300) in this study has small graphitic domains with well-developed graphene layers, a large interlayer spacing (0.403 nm), and a high micropore surface area (207.5 m2 g-1). When tested as an anode in an NIB, C-1300 exhibited an initial Coulombic efficiency of 68% and a high reversible capacity of 297 mA h g-1 at 50 mA g-1 after 50 cycles. The high capacity of 199 mA h g-1 at less than 0.1 V with a flat voltage profile and an extremely low charge-discharge voltage hysteresis (<0.03 V) make C-1300 a promising energy-dense electrode material. In addition, C-1300 exhibited an excellent high-rate performance of 116 mA h g-1 at 2.5 A g-1 and showed stable cycling retention (0.2% capacity decay per cycle after 500 cycles). By comparing the properties of the lignin-derived carbon with oak sawdust-derived and sugar-derived carbons and a low-temperature carbonized sample (900 °C), the reasons for the excellent performance of C-1300 were determined to result from facilitated Na+-ion transport to the graphitic layer and the microporous regions that penetrate through the less defective and enlarged interlayer spacings.

Kinetic analysis of cattle manure pyrolysis process with a novel two‐step method: Pseudo‐component model coupled with multipeak gaussian fitting

A novel two‐step method is proposed to conduct the pseudo‐component model for cattle manure pyrolysis process. The weight coefficient of pseudo‐components firstly are identified accurately by Gaussian multipeak fitting method based on the DTG data of cattle manure, and then the kinetic parameters for each pseudo‐component including reaction order, activation energies (Ei) and pre‐exponential factor (Ai), are obtained by the reaction‐order mechanism function and Coats‐Redfern method. The results showed that the decomposition process of cattle manure should be characterized by five pseudo‐components (extractives, hemicellulose, cellulose, lignin, and volatilizable carbonaceous materials). The corresponding reaction orders were 1.6, 1.8, 1.9, 1.3, and 1.8, respectively. The Ei were ranged from 42.54 to 527.02 kJ mol−1 for five pseudo‐components. The pseudo‐component model coupled with multipeak Gaussian fitting could describe the kinetic process of cattle manure decomposition very well, and provide useful data for the design of a thermal decomposition processing system and the kinetic analysis of pyrolysis process of other solid wastes. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1618–1625, 2018

Characterization of labile organic matter in Pleistocene permafrost (NE Siberia), using Thermally assisted Hydrolysis and Methylation (THM-GC-MS)

Pleistocene yedoma sediments store large amounts of soil organic matter (SOM) and are vulnerable to permafrost degradation. Here we contribute to our understanding of yedoma SOM dynamics and potential response to thaw, by molecular characterization of samples from a 5.7 m yedoma exposure, as well as upper permafrost samples that were previously incubated, using Thermally assisted Hydrolysis and Methylation (THM-GC-MS). In general, the SOM is derived from aliphatic material (including cutin and suberin), phenols (lignin, sphagnum acid), polysaccharides and N-containing components (largely microbial SOM). Soil organic carbon (SOC) content and molecular SOM composition follow a sawtooth pattern where local maxima in SOC coincide with lignin and aliphatic material that experienced only slight degradation, and minima with degraded plant-derived SOM and microbial tissue, representing a stratified cryopedolith. The SOC-depleted top 0.9 m (active layer and transition zone) is enriched in microbial SOM probably due to recent thawing. Comparison with CO2 respiration rates indicates that SOM of microbial origin (low C/N) is more labile than aliphatic SOM from well-preserved plant tissue (high C/N). However, we argue that the more stable aliphatic SOM in SOC-rich layers might also be vulnerable to decay, which could, due to its abundance in SOC-rich layers, dominate overall Yedoma C losses due to thermal erosion.

Effects of Thermal Stabilization and Electron Beam Irradiation on the Characteristics of Lignin Extracted from Black Liquor

In the present work, lignin extracted from black liquor, which is industrial waste of pulp manufacturing. The extracted lignin was irradiated at various electron beam intensities from 100 to 1000 kGy. Also, the extracted lignin was thermally stabilized by heat treatment process. The characteristics of the stabilized and irradiated lignin materials were examined by means of TGA, ATR-FTIR, EA, and SEM. The ATR-FTIR result shows that both stabilized and irradiated lignin samples exhibit the decrease of characteristic absorption peaks, indicating the presence of guaiacyl and syringyl groups in the lignin structure. It reveals that the irradiation done to the ‘as-extracted’ lignin with appropriate electron beam intensity provides an efficiency as thermal stabilization of the lignin, suggesting that electron beam irradiation may apply directly to the extracted lignin, prior to carbonization the lignin without thermal stabilization process.

Propriedades físicas e químicas da madeira de cerne e alburno de Cryptomeria japonica

The study of the physical properties and chemical composition of the wood are of great importance for being related to industrial transformation as well as its aptness the most varied forms of use. On this basis, this study aimed to evaluate the chemical and physical properties of Cryptomeria japonica in wood samples for the heartwood and sapwood. The chemical properties of the content of extractives, lignin and inorganic materials content and hydrogenic potential (pH) were determined. The physical properties related to determination of density and dimensional stability, were evaluated by using 951 samples. In general, both wood samples presented chemical properties compatible with the literature for Cryptomeria japonica. For both samples a low content of extractives was obtained, being lower in the sapwood. The results indicated that the species presented density from low to medium; it is similar to both wood samples. Regarding the dimensional stability Cryptomeria japonica was rated as good stability.

Compositional changes and molecular transformations of dissolved organic matter during the arctic spring floods in the lower Churchill watershed (Northern Manitoba, Canada)

The spring flood season in Northern aquatic systems is characterized by rapid changes in river discharge and fluxes of organic and inorganic species, yet remains under sampled. In this study, we examine the molecular characteristics and transformations of dissolved organic matter (DOM) during the Arctic spring season at three locations in the lower Churchill River watershed. Characteristics including dissolved organic carbon concentrations, optical properties (i.e. absorbance and, excitation-emission matrix fluorescence coupled with parallel factor analysis, EEM-PARAFAC) and molecular characterization using high resolution mass spectrometry (HR-MS) were assessed. As spring floods progressed, a significant reduction in DOM spectral slope (S275–295) and an increase in absorbance (a270) were observed suggesting an increase in DOM molecular weight and concentrations at all sampled locations. A maximum in HR-MS lignin-class compounds coincided with peak flow at all sampled locations, further validated with an increase in PARAFAC humic-like components and a minimum in S275–295. Principal component analyses revealed that both protein and aromatic humic-like material measured by HR-MS and EEM-PARAFAC, respectively, were significantly correlated (ANOVA, p < 0.05), demonstrating similarities in both techniques. Based on network analysis of HR-MS assigned formula, the highest peak flow day was characterized by a maximum in homologous DOM of C2H2O and C2H4 additions, suggesting structural similarities in newly deposited lignin and humic material. Overall, the progression of the spring freshet shifted the lower Churchill River watershed from an environment rich in proteins and lipids to an aquatic system more abundant in lignin, aromatic and humic DOM.

Lignin and ash balances of sulfur dioxide-ethanol-water fractionation of sugarcane straw

Lignin and ash material balances of SO2-ethanol–water (AVAP®) fractionation of sugarcane (SC) straw were thoroughly studied at various conditions. Most of straw lignin and ash dissolve in the liquor and 40–80% of lignin is precipitated after ethanol removal as a pure (∼99%) and sulfur-lean (<2%) fraction. Most of the acid-soluble ash and its elements (Na, K, Fe, Al) as well as large portion of silica are removed from the fiber phase. Straw lignin behavior exhibited differences compared to wood lignin including high apparent content in fiber, higher degree of sulfonation of dissolved lignin, and dense char-like precipitate formation upon ethanol removal. Variation in fractionation conditions did not have significant effect on lignin properties, while post-sulfonation was capable of changing its form from char-like to colloidal precipitate.

Lignin accumulation and biosynthetic enzyme activities in relation to postharvest firmness of fresh waxy corn

Lignification and changes in the enzymes involved in lignin biosynthesis were investigated in relation to the reduced tenderness occurring during the postharvest storage of fresh waxy corn at 20 °C. The firmness of the corn and its lignin and polyphenol contents increased as storage time increased. The lignin content was significantly correlated (p .05) effect of polyphenol oxidase or cinnamyl alcohol dehydrogenase (CAD) on the lignin content was observed. Practical applications Tenderness is a main factor in sensory quality of fresh waxy corn. Secondary cell wall lignifications induced by phenylpropanoid pathway is the main reason of tenderness decline for postharvest fresh waxy corn. But little information of lignin accumulation of fresh waxy corn is obtained from the present studies. Analyzing the changes of lignin and related precursor materials, enzyme activities will help to comprehensively understand the regulatory mechanism of postharvest lignification of fresh waxy corn, which can provide suitable methods to delay postharvest lignin accumulation, and maintain the eating quality of fresh waxy corn.

Applying Direct Yellow 11 to a modified Simons’ staining assay

For quantification of overall fiber accessibility of lignocellulosic substrates, Direct Yellow 11 (C.I. 40000) is a suitable alternative to the discontinued Pylam Products’ dye Direct Orange 15 (C.I. 40002/40003). In this study we present a side-by-side comparison between the two azo-stilbene dyes. We characterize individual dye fractions and provide equations to determine individual concentrations. We present a modified Simons’ staining protocol incorporating the high molecular weight fraction of Direct Yellow 11. We perform tests on lignin, cellulosic, and lignocellulosic materials. In all tests, the two dyes perform similarly and satisfy many accessibility measurement criteria. We demonstrate that the adsorption of Direct Yellow 11 onto a substrate correlates with that substrate’s propensity for enzymatic hydrolysis. We confirm this correlation on a series of organic solvent pretreatments and on a series of lignocellulosic substrates. Finally, we outline the inherent limitations of performing adsorption experiments with Direct Yellow 11 and other high molecular weight dyes.

Systematic Parameterization of Lignin for the Charmm Force Field

Lignin is an abundant aromatic biopolymer within plant cell walls formed through radical coupling chemistry, whose composition and topology can vary greatly depending on the biomass source. Computational modeling provides a complementary approach to traditional experimental techniques to probe lignin interactions, lignin structure, and lignin material properties. However, current modeling approaches are limited based on the subset of lignin chemistries covered by existing lignin force fields. To fill the gap, we developed a comprehensive lignin force field that accounts for more lignin–lignin and lignin–carbohydrate interlinkages than existing lignin force fields, and also greatly expands the lignin monomer chemistries that can be modeled beyond simple alcohols and into the rich mixture of natural lignin varieties. The development of this force field utilizes recent developments in parameterization methodology, and synthesizes them into a workflow that combines target data from multiple molecules simultaneously into a single consistent and comprehensive parameter set. The parameter set represents a significant improvement to alternatives for atomic modeling of diverse lignin topologies, more accurately reproducing experimental observables while also significantly reducing the error relative to quantum calculations. The improved energetics, as well as the rigid adherence to CHARMM parameterization philosophy, enables simulation of lignin within its biological context with greater accuracy than was previously possible. The lignin force field presented here is therefore a crucial first step towards modeling lignin structure across a broad range of environments, including within plant cell walls where lignin is complexed with carbohydrates and deconstructed by bacterial or fungal enzymes, or as it exists within industrial solvent mixtures. Future simulations enabled by this updated lignin force field will thus lead to better chemical and structural understanding of lignin, providing new insight into its role in biomass recalcitrance or probing the potential for lignin to be used within industrial processes.

Heat recovery in compost piles for building applications

This work proposes an estimation of the possible heat recovery of self-heating compost piles for building applications. The energy released during the aerobic composting of lignin and cellulose-based materials is computed by solving an inverse problem. The method consists first in an experimental phase with measurement of the temperature within the heap, then a numerical procedure allows for the inverse identification of the heat production due to the chemical reaction of composting. The simulation results show a good accordance with the experiments for the chosen source-term model. Comparing the results to the theoretical values for the energy released by aerobic composting provides an estimate for the efficiency of the reaction. The reached temperatures and recovered energy fit with the order of magnitude of building needs.

Signatures of Biomass Burning Aerosols in the Plume of a Saltmarsh Wildfire in South Texas.

The most conventional and abundant tracers of biomass combustion in aerosol particles include potassium and biomarkers derived from thermally altered cellulose/hemicellulose (anhydrosugars) and lignin (methoxyphenols). However, little is known of the role biomass combustion plays as a particulate source of major plant polymers to the atmosphere. Here, concentrations of solvent-extractable anhydrosugars and methoxyphenols are compared to the yields of polymeric lignin oxidation products (LOPs) during a smoke plume event in Houston, Texas. Downwind aerosol samples (PM2.5) were collected surrounding a two-day wildfire in the McFaddin National Wildlife Refuge, 125 km southeast of Houston, which was 12-16 h directly downwind during the peak of the burn. Concentrations of all organic markers, potassium, and calcium increased by a factor of 2-13 within 1-2 days of the start of the fire and dropped to prefire levels 3 days after the peak event. Source signatures of anhydrosugars and methoxyphenols during the peak of the plume were identical to those of grass charcoals collected from the site, confirming the use of charcoals as end-members for source input reconstruction during atmospheric transport. An enrichment factor of 20 in the anhydrosugar to methoxyphenol ratio of aerosols versus charcoals can be explained partially by differences in degradation rate constants between the biomarker groups. LOPs comprised 73-91% of all lignin material in the aerosols, pointing to fires as major sources of primary biogenic aerosol particles in which lignin phenols occur predominantly in polymeric form.

Pyrrolidinium Ionic Liquids as Effective Solvents for Lignin Extraction and Enzymatic Hydrolysis of Lignocelluloses

Lignocellulosic biomass as a renewable and valuable resource has been a very active research area during recent years. Ionic liquids (ILs) are an attractive approach for the pretreatment of lignocelluloses. In this work, a series of pyrrolidinium-based ionic liquids were prepared simply and were investigated for the pretreatment of corn stalk at 90 °C for 30 min. The characteristics of regenerated lignin and cellulose-rich materials were determined by Fourier transform infrared spectroscopy (FTIR) analysis. Both ILs and ILs/H2O were studied. Notably, 10.17% lignin based on the original corn stalk was recovered with [Hmp]Cl-pretreatment; 21.34% and 15.83% reducing sugar based on the original corn stalk were observed during pretreatment with [Hmp]HSO4/H2O and [Hmp]Cl/H2O pretreatment, respectively; 80.54% of reducing sugar was obtained based on the cellulose-rich materials with [Hmp]Cl/H2O-pretreatment. Also, the glucose and cellobiose yields were 73.82% and 8.64%, respectively.