Lignin Removal Research Articles

Investigation into the characteristics of bagasse processed with 3C-DES and the production of chemimechanical pulp for pulp molded

Pulp molded generated from renewable bagasse as biodegradable packaging materials has been widely viewed as an eco-friendly and cheap way to substitute the current huge consumption of nondegradable plastics, and deep eutectic solvents (DES) pretreatment are a promising approach to obtain high-yield pulp efficiently and sustainably. However, mainstream binary-component DES still suffers issues of high viscosity and corrosiveness. This study put forward a ternary-component DES (3C-DES) with the addition of ethylene glycol (EG) into choline chloride (ChCl) and P-toluenesulfonic acid (PTSA) and examined pretreatment performance and optimal DES ratio for thread rolling bagasse via compositional analysis and physicochemical characterization. Moreover, density functional theory calculations were used to reveal structures and weak interactions of different ratios of 3C-DES, and a novel 3C-DES pretreatment chemical-mechanical pulp and pulp molded were finally prepared. The results indicate that the 3C-DES with ChCl:PTSA:EG molar ratio of 1:1:3 is most effective, evidenced by more than 97.94% lignin removals. The 3C-DES pretreated mechanical pulp exhibits superior fiber properties, whereas the hot-pressed pulp molded shows excellent physical properties and thermal stability. Thus, the proposed 3C-DES has great potential to obtain high-yield high-performance pulp molded with low cost and environmental sustainability.

Delignification of Different Lignocellulosic Biomass Using Hydrogen Peroxide and Acetic Acid (HPAC)

Lignocellulosic biomass will soon become the key source of feedstock for bioenergy to combat the impact of global warming and the depletion of fossil fuel resources. Lignin separation costs have been a key obstacle to bioenergy generation from lignocellulosic biomass. Pulp and paper, biofuel, and biomaterials sectors depend on wood delignification. This study examines delignification trends and advances, including standard and new methods. The study begins by explaining how delignification improves wood processability and value. It describes lignin's chemical structure and properties, highlighting its role in wood's mechanical and chemical qualities. Lignin from diverse lignocellulosic biomass sources is delignified using hydrogen peroxide and acetic acid in this study. A 1:1 hydrogen peroxide-acetic acid volume ratio was used after particle reduction. Experimental results show 96%, 89%, and 80% lignin removal efficiency for Ako, Mahogany, and mixed sawdust, respectively. A 30-minute reaction at 80°C yielded these results. The hydrogen peroxide-acetic acid mixture dignifies well and may be used in lignocellulosic biomass processing. This study also provides insights into optimizing delignification procedures and suggests approaches to improve the industrial use of lignocellulosic biomass. This study reveals that HPAC dignifies wood well. Understanding HPAC's role in the delignification of wood products could lead to developing an HPAC-based pretreatment technique that lowers the cost of biofuel generation from lignocellulosic biomass.

Extraction of cellulose from soybean hulls for the development of polymer matrix composites with fishtail palm fibers

This study aims to extract and characterize cellulose nanocrystals (CNCs) from soybean hulls, and investigate their application as reinforcement in fishtail palm leaf stalk fiber (FPLSF) composites. CNCs were extracted through a multistep process involving alkalization, bleaching, acid hydrolysis and mechanical fibrillation. Analysis confirmed the transformation of cellulose I to cellulose II, yielding nanocrystals with 70.58% crystallinity index and thermal degradation peak at 371 °C. FTIR analysis verified removal of lignin and hemicellulose after extraction. The extracted CNCs were incorporated into FPLSF-epoxy composites at 2.5-10 wt% loading. Results showed 7.5 wt% CNCs (FT/SH4) provided optimal mechanical properties, with 51.4 MPa tensile strength, 46.09 MPa flexural strength and 36.47 kJ mm−2 impact strength. Lower CNC percentages showed significantly inferior properties due to poor fiber-matrix interfacial bonding. Overall, extracted soybean hull CNCs demonstrated good reinforcement capabilities for natural fiber composites. This provides a sustainable application route for agricultural residues and contributes to the development of high-performance biocomposites.

Enhancing Enzymatic Hydrolysis and Delignification of Sugarcane Bagasse Using Different Concentrations of Sodium Alkaline Pretreatment

Lignin, being highly resistant, needs to be eliminated in the process of extraction of soluble reducing sugar and bioethanol production from lignocellulosic biomass. In the present work, pretreatment of sugarcane bagasse (SCB) was performed using NaOH of various concentrations (1-5%) to facilitate delignification. The hydrolysis efficiency of pretreated SCB was evaluated at different reaction times by the production of reducing sugar using the Cellic CTec2 enzyme. The maximum cellulose content of 57.6% and lignin removal of 62.04% were observed with 2% sodium hydroxide at 121°C autoclaved for 60 min. The hemicellulose content decreased with increasing NaOH concentration with the maximum decrease of 13.6% from native bagasse having 26.5% xylan content. The microstructure, morphology, and chemical composition of SCB were analyzed using Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform InfraRed (FTIR), and XRD. The hydrolysis with 10 FPU.g-1 of enzyme at 48 h of reaction time shows a maximum yield of 12.34 g.L-1 corresponding to 55.53 ± 0.45% at 2% NaOH pretreated SCB. This study claims that lignin components exhibited the highest susceptibility to NaOH pretreatment, which directly affects enzymatic hydrolysis.

Effect of Mercerization on the Crystallographic, Macromolecular, and Thermal Properties of Plantain Fibers for Fiber Reinforced Composite

In this research, natural fibers (NF) were obtained from plantain pseudo stem. The extracted plantain fibers (PF) were modified by mercerization under diverse conditions in terms of treatment time and concentration. The crystallographic structures and macromolecular properties, and surface extracted PF were all influenced by the modification process. Improvements in thermal properties were observed along with increases in the crystallite size, and degree of crystallinity as revealed by x-ray diffraction (XRD) analysis. FTIR spectroscopy confirmed partial removal of wax, lignin, and hemicellulose. Bulk density was also observed to change under treatment conditions, while Scanning electron microscope (SEM) imagery demonstrates how the treatment altered the surface of the PF. A considerable change in the macromolecular and structural characteristics of plantain fiber was observed under optimum treatment conditions.

Carboxylmethyl cellulose produced from wood sawdust for improving properties of sodium alginate hydrogel in dye adsorption

Cellulose-based materials have shown immense potential for diverse applications because of their attractive properties such as excellent mechanical properties, rich hydroxyl groups for modification, and natural properties with recyclability, nontoxicity, biocompatibility, biodegradability, and environmental friendliness. This study aimed to optimize cellulose extraction from wood sawdust using deep eutectic solution (DES) treatments for the preparation of carboxymethyl cellulose (CMC) and to evaluate the application of CMC in sodium alginate (SA) microgel for dye adsorption. Cellulose extractions were optimized in reduced chemical treatment conditions with high cellulose contents (88.19 %), and selectively increased lignin removal (87.23 %). The analyses by SEM, XRD, and FT-IR revealed that carboxymethylation has successfully transformed cellulose into CMC to facilitate the significantly improved water solubility and swelling ability. The TGA curve of CMC showed a higher thermal stability (residual weight of 52 % at 300 °C) compared to unmodified cellulose due to the decomposition of the amorphous regions during the carboxymethylation. The combined biodegradable SA and water-soluble CMC composite microgels were successfully fabricated via cross-linking with calcium chloride using a microfluidic approach. The incorporation of CMC into SA microgel had enhanced mechanical properties, adsorption capacities of 160.87 and 141.48 mg/g, and adsorption–desorption efficiencies of 96.84 % and 95.41 % for crystal violet and trypan blue respectively after five cycles. The adsorption processes of both dyes can be described by Sips adsorption isotherms and pseudo-second-order kinetic models, verifying the chemical interaction-assisted process. This simple green CMC/SA adsorbent has the potential to significantly enhance the adsorption capacity of dye removal from wastewater.

Enhanced humification via lignocellulosic pretreatment in remediation of agricultural solid waste

Stover and manure are the main solid waste in agricultural industry. The generation of stover and manure could lead to serious environmental pollution if not handled properly. Composting is the potential greener solution to remediate and reduce agricultural solid waste, through which stover and manure could be remediated and converted into organic fertilizer, but the long composting period and low efficiency of humic substance production are the key constraints in such remediation approach. In this study, we explore the effect of lignocellulose selective removal on composting by performing chemical pretreatment on agricultural waste followed by utilization of biochar to assist in the remediation by co-composting treatment and reveal the impacts of different lignocellulose component on organic fertilizer production. Aiming to discover the key factors that influence humification during composting process and improve the composting quality as well as comprehensive utilization of agricultural solid waste. The results demonstrated that the removal of selective lignin or hemicellulose led to the shift of abundances lignocellulose-degrading bacteria, which in turn accelerated the degradation of lignocellulose by almost 51.2%. The process also facilitated the remediation of organic waste via humification and increased the humic acid level and HA/FA ratio in just 22 days. The richness of media relies on their lignocellulose content, which is negatively correlated with total nitrogen content, humic acid (HA) content, germination index (GI), and pH, but positively correlated with fulvic acid (FA) and total organic carbon (TOC). The work provides a potential cost effective and efficient framework for agricultural solid waste remediation and reduction.

Construction of Nanofibrillar Networked Wood Aerogels Derived from Typical Softwood and Hardwood: A Comparative Study on the In Situ Formation Mechanism of Nanofibrillar Networks.

The construction of networks within natural wood (NW) lumens to produce porous wood aerogels (WAs) with fascinating characteristics of being lightweight, flexible, and porous is significant for the high value-added utilization of wood. Nonetheless, how wood species affect the structure and properties of WAs has not been comprehensively investigated. Herein, typical softwood of fir and hardwoods of poplar and balsa are employed to fabricate WAs with abundant nanofibrillar networks using the method of lignin removal and nanofibril's in situ regeneration. Benefiting from the avoidance of xylem ray restriction and the exposure of the cellulose framework, hardwood has a stronger tendency to form nanofibrillar networks compared to softwood. Specifically, a larger and more evenly distributed network structure is displayed in the lumens of balsa WAs (WA-3) with a low density (59 kg m-3), a high porosity (96%), and high compressive properties (strain = 40%; maximum stress = 0.42 MPa; height retention = 100%) because of the unique structure and properties of WA-3. Comparatively, the specific surface area (SSA) exhibits 25-, 27-, and 34-fold increments in the cases of fir WAs (WA-1), poplar WAs (WA-2), and WA-3. The formation of nanofibrillar networks depends on the low-density and thin cell walls of hardwood. This work offers a foundation for investigating the formation mechanisms of nanonetworks and for expanding the potential applications of WAs.

Pretreatments Applied to Wheat Straw to Obtain Bioethanol

This work is a comprehensive study focusing on various methods for processing wheat straw to enhance its suitability for bioethanol production. It delves into mechanical, physical, chemical, and biological pretreatments, each aimed at improving the enzymatic hydrolysis and fermentation processes necessary for bioethanol production. Mechanical and physical pretreatments involve reducing the size of wheat straw to improve enzymatic hydrolysis. Physical methods include heating and irradiation, which alter the structural properties of wheat straw. Chemical pretreatments involve using acids, alkalis, and organic solvents to remove lignin and hemicellulose, making cellulose more accessible for hydrolysis. Biological pretreatments utilize microorganisms and fungi to degrade lignin and other complex compounds, enhancing the breakdown of cellulose. The study presents data on the effectiveness of these treatments in terms of lignin removal, sugar yield, and overall bioethanol production efficiency. The research is aligned with the global move towards renewable energy sources and emphasizes the importance of utilizing agricultural waste, like wheat straw, for sustainable energy production.

Degradation selectivity for bamboo fiber and parenchyma lignin-carbohydrates complexes (LCC) esters

The degradation of lignin-carbohydrate complex (LCC) esters has been proven to be crucial for the selective separation of lignocellulosic components. This study utilized Raman microspectroscopy to image the preferential degradation of lignin and LCC esters from the bamboo wall during successive NaOH (0.2 to 5.0 % w/w), H2SO4 (1 to 8 % v/v), and NaClO2 (5 to 20 min) treatments. Raman imaging showed that lignin and LCC esters were selectively removed from the middle lamella of fibers and the secondary wall of parenchyma during NaOH and NaClO2 treatments. In contrast, H2SO4 primarily caused the simultaneous removal of lignin and LCC esters from the fiber wall under harsh conditions (8 %), while the middle lamella of parenchyma was less affected, both morphologically and topochemically. Raman spectral analysis indicated that the band intensity at 1605 cm−1 for lignin and at 1173 cm−1 for LCC esters decreased by >87.0 % in the highly lignified parenchyma secondary wall after a 5.0 % NaOH treatment, while the decrease was <67 % in the fiber wall. Interestingly, a strong linear correlation was observed between LCC esters and carbohydrates in the parenchyma (R2 > 0.912). These findings provide important insights into the graded and classified utilization of bamboo resources.

Microporous and Mesoporous Activated Carbons from Tea Stalk and Tea Stalk Pulps: Effect of Lignin Removal by One-Step and Two-Step Organosolv Treatment

Delignification is a crucial pretreatment in the production of diverse value-added products from lignocellulosics. While modifying the surface functional groups, delignification also increases the specific surface area by providing a porous structure to the lignocellulosic biomass. Hydrothermal pretreatment can be used prior to delignification, to recover hemicellulose and boost delignification. By removing lignin and hemicellulose, cellulose-rich pulp becomes more accessible for activation. In the present study, three different activated carbons were prepared: activated carbon from tea stalk itself (ATS), activated carbon from tea stalk pulp obtained by using glycerol organosolv pretreatment (ATP), activated carbon from tea stalk hydrochar pulp obtained by using sequential hydrothermal pretreatment-organosolv delignification (AHTP). Each precursor was carbonized (at 800 °C) in the presence of KOH (KOH/precursor: 2/1). Activated carbons were characterized for their elemental content, surface functional groups, thermal stability, crystallinity, surface morphology, surface area and porous structure using elemental analysis (C-H-N-S), FTIR, TGA, XRD, SEM and, BET analysis, respectively. While hydrothermal pretreatment prior to organosolv pulping reduced the delignification yield, it also altered the pore structure of activated carbon. Among the activated carbons, only ATS had microporous structure with an average pore radius of 1 nm. ATP had the highest surface area (2056.72 m2/g) and micropore volume (0.81 cm3/g). Having mesopores (with an average pore radius of 5.74 nm) in its structure, AHTP had the least micropore volume (0.464 cm3/g) and surface area (1179.71 m2/g). The presence of micro and mesopores broadens the potential applications of activated carbon ranging from environmental applications to energy storage.

Obtaining micrometric-scale hollow fibers from wastes aged coir by oxidative chloro-sulfonation of lignin: HClO/H2SO4

Coconut fiber is a lignocellulosic material extracted from the coconut mesocarp. Due to its mechanical properties, coconut fiber has been used as reinforcement in composite materials, which contrasts with a relatively small number of studies where coconut fiber is evaluated as a functional polymeric material. In this research, the extraction and transformation of aged coconut biofibers are proposed for their use as substrate/support into making of functional polymers, specifically for slow release of fertilizers. An interesting property of this material is its hollow-type morphology at micrometric scale. Thus, coconut biofibers (BFs) were mechanically extracted and delignified using mixed-oxidizing system constituted by NaClO and H2SO4 at different pH values (2.0 ≤ pH ≤ 12.0). BFs were thermal, spectroscopic and functionally characterized by different techniques, including infrared and ultraviolet-visible spectroscopies, thermogravimetric analysis, scanning electron microscopy, among others. The bleaching of the fibers and the removal of lignin were evidenced by microscopy. The best results of this stage were seen at pH 4.0, 7.0 and 8.0, being possible obtain different materials depending on three acidity regimens (2.0 ≤ pH ≤ 4.0, 4.0 < pH ≤ 8.0 and 8.0 < pH ≤ 12.0). In addition, delignification achieved is function on pH with a value close to 80 % according to the change of surface color intensity. It is concluded that coconut biofibers are natural structure which can be used as support for the making of functional materials.

Efficient hemicellulose removal from lignocellulose by induced electric field-aided dilute acid pretreatment

This study evaluated the effectiveness of induced electric field (IEF) as a novel electrotechnology to assist dilute acid pretreatment of wheat straw (WS) at atmospheric pressure and low temperature (90 °C). The effects of acid concentration and duration on cellulose recovery, hemicellulose and lignin removal were investigated. Meanwhile, the differences between IEF pretreatment and hydrothermal pretreatment were compared by quantitative and qualitative analysis. The optimal pretreatment condition was acid concentration 1 % with the period of 5 h. Under the parameters, the hemicellulose removal of WS after IEF pretreatment was up to 73.6 %, and the enzymatic efficiency was 55.8 %. In addition, the irregular surface morphology, diminished functional groups associated with hemicellulose, increased specific surface area and pore volume, as well as improved thermal stability of the residual WS support the remarkable effect of IEF pretreatment. The feasibility of IEF pretreatment is might be due to the fact that the magneto-induced electric field promotes ionization of H+ and formation of hydrated hydrogen ions, increasing the acidity of the medium. Secondly, electroporation disrupts the anti-degradation structure of WS and increases the accessibility of cellulose to cellulases. It indicated that IEF is a green and efficient strategy for assisting the separation of hemicellulose from lignocellulose.

Green conversion of delignified sorghum straw and polyethylene glycol into form-stable phase change materials with promising solar energy capture, transition, and storage capabilities

Phase change materials (PCMs) have attracted considerable attention as a thermal energy management technology for thermal storage. However, achieving high energy-storing abilities, low leakage rates, and solar absorption abilities simultaneously in PCMs remains greatly challenging. This research proposed a green strategy for preparing sorghum straw-based PCMs. By facile delignification and solvothermal process, delignified sorghum straw (DSS) and carbon quantum dots (CQDs) derived from removal lignin are prepared. The obtained PEG@CQDs/DSS possessed considerable reusable stabilities, excellent photo-thermal conversion properties, and thermal energy management capacities due to the delicate micropores and intrinsic noncovalent interactions among components. Especially, the PEG@CQDs-7.5/DSS exhibited superior solar-thermal conversion capabilities (with conducive photo-thermal conversion efficiency ~90.84%), and kept stable after 100 cycles of heating and cooling, in which the melting enthalpy value is ~168.1 J/g (enthalpy efficiency of ~91.11%). In conclusion, the synthesized PCMs showed potential for application in energy-saving and building thermal management.

Transcriptomic and metabolomic analysis reveals the influence of carbohydrates on lignin degradation mediated by Bacillus amyloliquefaciens

IntroductionLigninolytic bacteria can secrete extracellular enzymes to depolymerize lignin into small-molecular aromatics that are subsequently metabolized and funneled into the TCA cycle. Carbohydrates, which are the preferred carbon sources of bacteria, influence the metabolism of lignin-derived aromatics through bacteria.MethodsIn this study, untargeted metabolomics and transcriptomics analyses were performed to investigate the effect of carbohydrates on lignin degradation mediated by Bacillus amyloliquefaciens MN-13, a strain with lignin-degrading activity that was isolated in our previous work.ResultsThe results demonstrated that the cell growth of the MN-13 strain and lignin removal were promoted when carbohydrates such as glucose and sodium carboxymethyl cellulose were added to an alkaline lignin-minimal salt medium (AL-MSM) culture. Metabolomics analysis showed that lignin depolymerization took place outside the cells, and the addition of glucose regulated the uptake and metabolism of lignin-derived monomers and activated the downstream metabolism process in cells. In the transcriptomics analysis, 299 DEGs were screened after 24 h of inoculation in AL-MSM with free glucose and 2 g/L glucose, respectively, accounting for 8.3% of the total amount of annotated genes. These DEGs were primarily assigned to 30 subcategories, including flagellar assembly, the PTS system, RNA degradation, glycolysis/gluconeogenesis, the TCA cycle, pyruvate metabolism, and tryptophan metabolism. These subcategories were closely associated with the cell structure, generation of cellular energy, and precursors for biosynthetic pathways, based on a − log 10 (P adjust) value in the KEGG pathway analysis.ConclusionIn summary, the addition of glucose increased lignin degradation mediated by the MN-13 strain through regulating glycolysis, TCA cycle, and central carbon metabolism.

Novel approach for corn straw biorefineries: Production of xylooligosaccharides, lignin and ethanol by nicotinic acid hydrolysis and pentanol pretreatment

The productive separation and conversion of corn straw offers significant prospects for the economic viability of biorefineries centered on straw resources. In this work, a graded utilization method was proposed to produce xylo-oligosaccharides (XOS), ethanol and lignin from corn straw by nicotinic acid (NA) hydrolysis and water/pentanol pretreatment. A XOS yield of 52.6 % was achieved under optimized conditions of 100 mM NA, 170 °C and 30 min. The solid residue was directly treated with water/pentanol, achieving a lignin removal rate of 79.7 %, and the total XOS yield was improved to 62.6 %. The lignin recovered from pentanol had a high purity of 97.6 %, with high phenolic OH content. Simultaneous saccharification and fermentation of final residue resulted in an ethanol yield of 92.0 %, which yielded 55.3 g/L ethanol. Thus, NA hydrolysis and water/pentanol pretreatment provided an efficient, environmentally friendly approach to fractionate corn straw for the co-production of XOS, ethanol, and lignin.

Efficient Fast Fractionation of Biomass Using a Diol-Based Deep Eutectic Solvent for Facilitating Enzymatic Hydrolysis and Obtaining High-Quality Lignin.

Current DES pretreatment is often performed under relatively severe conditions with high temperature, long time, and high DES usage. This work studied a short-time diol DES (deep eutectic solvent) pretreatment under mild conditions to fractionate the bamboo, facilitate enzymatic hydrolysis, and obtain high-quality lignin. At an optimized condition of 130 °C for only 10 min, lignin and xylan removal reached 61.34 % and 84.15 %, with residual glucan showing a ~90 % enzymatic hydrolysis yield. Equally important, the dissolved lignin could be readily recovered with 97.51 % yield, exhibiting 96.65 % β-O-4 preservation. The fractionation and lignin protection mechanisms were unveiled by XRD, FTIR, cellulose-DP, 2D HSQC NMR, 31P NMR and GPC analysis. This study highlighted that short-time fractionation of bamboo can be achieved by a diol-based DES which is an ideal strategy to upgrade the lignocellulose biomass for high enzymatic hydrolysis yields and high-quality lignin stream.

Lignin impairs Cel7A degradation of in vitro lignified cellulose by impeding enzyme movement and not by acting as a sink

BackgroundCellulose degradation by cellulases has been studied for decades due to the potential of using lignocellulosic biomass as a sustainable source of bioethanol. In plant cell walls, cellulose is bonded together and strengthened by the polyphenolic polymer, lignin. Because lignin is tightly linked to cellulose and is not digestible by cellulases, is thought to play a dominant role in limiting the efficient enzymatic degradation of plant biomass. Removal of lignin via pretreatments currently limits the cost-efficient production of ethanol from cellulose, motivating the need for a better understanding of how lignin inhibits cellulase-catalyzed degradation of lignocellulose. Work to date using bulk assays has suggested three possible inhibition mechanisms: lignin blocks access of the enzyme to cellulose, lignin impedes progress of the enzyme along cellulose, or lignin binds cellulases directly and acts as a sink.ResultsWe used single-molecule fluorescence microscopy to investigate the nanoscale dynamics of Cel7A from Trichoderma reesei, as it binds to and moves along purified bacterial cellulose in vitro. Lignified cellulose was generated by polymerizing coniferyl alcohol onto purified bacterial cellulose, and the degree of lignin incorporation into the cellulose meshwork was analyzed by optical and electron microscopy. We found that Cel7A preferentially bound to regions of cellulose where lignin was absent, and that in regions of high lignin density, Cel7A binding was inhibited. With increasing degrees of lignification, there was a decrease in the fraction of Cel7A that moved along cellulose rather than statically binding. Furthermore, with increasing lignification, the velocity of processive Cel7A movement decreased, as did the distance that individual Cel7A molecules moved during processive runs.ConclusionsIn an in vitro system that mimics lignified cellulose in plant cell walls, lignin did not act as a sink to sequester Cel7A and prevent it from interacting with cellulose. Instead, lignin both blocked access of Cel7A to cellulose and impeded the processive movement of Cel7A along cellulose. This work implies that strategies for improving biofuel production efficiency should target weakening interactions between lignin and cellulose surface, and further suggest that nonspecific adsorption of Cel7A to lignin is likely not a dominant mechanism of inhibition.

Kinetic understanding of fiber surface lignin effects on cellulase adsorption and hydrolysis

Cellulase hydrolysis is strongly affected by adsorption, which is inhibited by the non-productive binding between cellulase and lignin. However, lignin-bonded cellulase has also been found to be active in hydrolysis. Thus, in this work, lignin effects on cellulase adsorption and hydrolysis were studied using fibers with various surface lignin contents and structures based on kinetics. The surface lignin was changed by mechanical refining. Cellulase adsorbed on lignin showed reactivity to hydrolyze cellulose nearby according to the kinetic results, which is, however, much weaker compared with that by cellulose-bonded cellulase. With the decrease of surface lignin, this reactivity is also decreasing. Both cellulase adsorption and hydrolysis were increasing at first and then decreasing with the decrease of surface lignin as well as the lignin re-adsorption. It was concluded that lignin plays an important role in cellulase adsorption and non-productive binding occurs more easily between cellulase and the re-adsorbed lignin, as well as the residual lignin. At a relatively high surface lignin level, lignin structural and distribution changes were found to have a better effect on cellulase hydrolysis compared with lignin removal.

Optimization of Process Parameters for Bamboo Fiber Extraction by Steam Explosion

ABSTRACT Bamboo fiber (BF) has emerged as a promising natural, environmentally friendly material for use in composite materials. The steam explosion process plays a crucial role in preparing BFs suitable for composites. In this study, the effects of solid–liquid ratio, explosion pressure, and explosion holding time on BF preparation were investigated by orthogonal experiments, and the structural and chemical changes occurring during the separation of BF were also investigated. The results showed that the combined method of alkali treatment and steam explosion successfully produced BFs with good morphology. The highest yield of fine fibers (39.07%) was obtained at a solid–liquid ratio of 2:1, explosion pressure of 2.2 MPa, and explosion holding time of 4 min. BFs obtained using the optimal values exhibited dispersed fiber bundles, partial removal of hemicellulose and lignin, and improved crystallinity. Furthermore, the hygroscopicity of BFs decreased, reaching a minimum of 15% under the optimal process conditions. The optimization of steam explosion parameters can help to improve the extraction efficiency of fine fibers for composites and promote the industrialization of BFs prepared by steam explosion.