Coupling the post-extraction process to remove residual lignin and alter the recalcitrant structures for improving the enzymatic digestibility of acid-pretreated bamboo residues

Enhanced flexibility of high-yield bamboo pulp fibers via cellulase immobilization within guar gum/polyacrylamide/polydopamine interpenetrating network hydrogels

Softness is a crucial criterion in assessing the comfort and usability of tissue paper. Flexible fibers contribute to the softness of the tissue paper by allowing the sheets to conform to the contours of the skin without feeling rough or abrasive. This study focuses on developing innovative CGG/APAM/PDA hydrogels with interpenetrating networks consisting of cationic guar gum, anionic polyacrylamide, and polydopamine for cellulase immobilization, aimed at improving bamboo fiber flexibility. Cellulase biomolecules are efficiently immobilized on CGG/APAM/PDA hydrogels through the Schiff base reaction. Immobilized cellulases have a wider pH applicability than free cellulases, good storage stability, and can maintain high relative activity at relatively high temperatures. The treatment of bamboo fibers with immobilized cellulase results in a significant increase in flexibility, reaching 6.90 × 1014 N·m2, which is 7.18 times higher than that of untreated fibers. The immobilization of cellulases using CGG/APAM/PDA hydrogels as carriers results in a substantial enhancement of storage stability, pH applicability, and inter-fiber bonding strength, as well as the capacity to sustain high relative enzymatic activity at elevated temperatures. The immobilization of cellulase within CGG/APAM/PDA interpenetrating network hydrogels presents a viable strategy for enhancing bamboo fiber flexibility, thereby expanding the accessibility of tissue products.

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.

Cellulose nanocrystals extracted from rice husk using the formic/peroxyformic acid process: isolation and structural characterization

Cellulose derived from biomass is a renewable resource with numerous applications. Using formic/peroxyformic acid at atmospheric pressure, cellulose nanocrystals (CNC) were isolated from rice husk (RH) in this study. This method was an excellent way to get rid of lignin and hemicelluloses from RH. The cellulose was subsequently acid hydrolyzed by H2SO4 (64%) for 30 minutes at 45 °C. The chemical and microstructure analysis showed that the lignin and hemicellulose contents of raw RH had been eliminated, and the crystallinity content of CNC was 67.16%. According to transmission electron microscopy (TEM) morphological analysis, CNC measured 19 ± 3.3 nm in diameter, 195 ± 24 nm in length, and 10.2 ± 6.8 in aspect ratio. The thermal stability of RH and CNC was also investigated using thermogravimetric analysis (TGA). These encouraging findings demonstrated the potential for reusing RH agricultural waste to create CNC and include nanocomposites as a reinforcing material.

Lignin, the Lignification Process, and Advanced, Lignin-Based Materials

At a time when environmental considerations are increasingly pushing for the application of circular economy concepts in materials science, lignin stands out as an under-used but promising and environmentally benign building block. This review focuses (A) on understanding what we mean with lignin, i.e., where it can be found and how it is produced in plants, devoting particular attention to the identity of lignols (including ferulates that are instrumental for integrating lignin with cell wall polysaccharides) and to the details of their coupling reactions and (B) on providing an overview how lignin can actually be employed as a component of materials in healthcare and energy applications, finally paying specific attention to the use of lignin in the development of organic shape-memory materials.

Sustainable Starch/Lignin Nanoparticle Composites Biofilms for Food Packaging Applications

Construction of sustainable composite biofilms from natural biopolymers are greatly promising for advanced packaging applications due to their biodegradable, biocompatible, and renewable properties. In this work, sustainable advanced food packaging films are developed by incorporating lignin nanoparticles (LNPs) as green nanofillers to starch films. This seamless combination of bio-nanofiller with biopolymer matrix is enabled by the uniform size of nanofillers and the strong interfacial hydrogen bonding. As a result, the as-prepared biocomposites exhibit enhanced mechanical properties, thermal stability, and antioxidant activity. Moreover, they also present outstanding ultraviolet (UV) irradiation shielding performance. As a proof of concept in the application of food packaging, we evaluate the effect of composite films on delaying oxidative deterioration of soybean oil. The results indicate our composite film could significantly decrease peroxide value (POV), saponification value (SV), and acid value (AV) to delay oxidation of soybean oil during storage. Overall, this work provides a simple and effective method for the preparation of starch-based films with enhanced antioxidant and barrier properties for advanced food packaging applications.

Preparation and plasticizing mechanism of deep eutectic solvent/lignin plasticized chitosan films

Chitosan (CS) is a natural biopolymer from crab shells known for its biocompatibility and biodegradability; however, CS films are extremely rigid, limiting their applications. In this study, CS composite films were prepared based on the selective dissolution of lignin by deep eutectic solvents (DES), and the toughening effect of this DES/lignin on a CS film substrate was examined, along with its corresponding mechanism. The addition of DES/lignin effectively increased the plasticity of the CS film, giving a maximum elongation at break of 62.6 % for the plasticized film, which is 12.5 times that of the CS film. Fourier transform infrared spectroscopy and nuclear magnetic resonance analyses showed that molecules in the DES/lignin complex interacted with CS to break the hydrogen bonds between the CS molecules; simultaneously, each molecule recombined with the CS molecules via hydrogen bonding. Thus, the rigidity of the CS molecular chain was weakened to achieve a plasticized CS film, thereby demonstrating the ability of DES/regenerated lignin to improve the toughness of CS films, which provides a reference for modifying plasticity and could lead to the broader utilization of CS films.

In-depth investigation of formic acid pretreatment for various biomasses: Chemical properties, structural features, and enzymatic hydrolysis

Formic acid pretreatment is a promising approach for fractionating biomass, and it has the advantages of efficient recycling and removal of hemicellulose and lignin. Biomass is one of the most plentiful resources on earth, yet its chemical structure differs significantly between woody and herbaceous biomass. The influence of formic acid pretreatment on the fractionation of woody and herbaceous biomasses, as well as changes in physical-chemical properties, was investigated in this study. The results indicated that formic acid is universal in the biorefinery of different biomass, however, herbaceous biomass had greater xylan and lignin removal than woody biomass (especially softwood). Formic acid pretreatment not only considerably improved the enzymatic efficiency of herbaceous biomass, but also had a good effect on the enzymatic efficiency of poplar. This study also found that the correlation between residual xylan content and enzymatic efficiency after pretreatment was much higher than that of lignin content.

An integrated process using acetic acid hydrolysis and deep eutectic solvent pretreatment for xylooligosaccharides and monosaccharides production from wheat bran

Organic acid hydrolysis for xylooligosaccharides (XOS) production from lignocelluloses provides the benefits of simple operation, rapid reaction and high XOS yield. However, no literature reported the XOS production from wheat bran (WB) by organic acid hydrolysis. In this paper, acetic acid (AA) hydrolysis was employed to produce XOS from WB. After AA hydrolysis (5 %, v/v, 170 °C, 20 min) of 100 g/L WB, the concentrations of X2, X3, X4, X5 and X6 were 2.4, 5.0, 1.9, 1.9 and 1.4 g/L respectively and the total XOS yield was 62.9 %, which was the highest among the previous researches. The arabinose yield reached 76.1 %. Then, AA-hydrolyzed WB was delignified by deep eutectic solvent (DES) pretreatment and the resulting residue had the glucose and xylose yields of 83.8 % and 54.8 %, respectively. This work offers a productive method for the conversion of WB into XOS, arabinose and glucose by AA hydrolysis and DES pretreatment.

Valorization of bamboo shoot shell waste for the coproduction of fermentable sugars and xylooligosaccharides

In this work, hydrothermal pretreatment (autohydrolysis) was coupled with endo-xylanase enzymatic hydrolysis for bamboo shoot shell (BSS) to produce glucose and valuable xylooligosaccharides (XOS) rich in xylobiose (X2) and xylotriose (X3). Results showed that the enzymatic hydrolysis efficiency of pretreated BSS residue reached 88.4% with addition of PEG during the hydrolysis process. To enrich the portions of X2–X3 in XOS, endo-xylanase was used to hydrolyze the XOS in the prehydrolysate, which was obtained at the optimum condition (170°C, 50 min). After enzymatic hydrolysis, the yield of XOS reached 25.6%, which contained 76.7% of X2–X3. Moreover, the prehydrolysate contained a low concentration of fermentation inhibitors (formic acid 0.7 g/L, acetic acid 2.6 g/L, furfural 0.7 g/L). Based on mass balance, 32.1 g of glucose and 6.6 g of XOS (containing 5.1 g of X2-X3) could be produced from 100.0 g of BSS by the coupled technology. These results indicate that BSS could be an economical feedstock for the production of glucose and XOS.

Valorization of lignocellulosic biomass for polyhydroxyalkanoate production: Status and perspectives

With the increasing concerns regarding climate, energy, and plastic crises, bio-based production of biodegradable polymers has become a dire necessity. Significant progress has been made in biotechnology for the production of biodegradable polymers from renewable resources to achieve the goal of zero plastic waste and a net-zero carbon bioeconomy. In this review, an overview of polyhydroxyalkanoate (PHA) production from lignocellulosic biomass (LCB) was presented. Having established LCB-based biorefinery with proper pretreatment techniques, various PHAs could be produced from LCB-derived sugars, hydrolysates, and/or aromatic mixtures employing microorganisms. This provides a clue for addressing the current environmental crises because "biodegradable polymers" could be produced from one of the most abundant resources that are renewable and sustainable in a "carbon-neutral process". Furthermore, the potential future of LCB-to-non-natural PHA production was discussed with particular reference to non-natural PHA biosynthesis methods and LCB-derived aromatic mixture biofunnelling systems.

Revealing the mechanism of surfactant-promoted enzymatic hydrolysis of dilute acid pretreated bamboo

To improve the enzymatic digestibility of dilute acid pretreated bamboo residue (DABR), surfactants including PEG 4000 and Tween 80 were added to prevent the non-productive adsorption between residual lignin and enzyme. At the optimal loadings (e.g., 0.2 and 0.3 g surfactant/g lignin), the enzymatic digestibility of DABR improved from 29.4% to 64.6% and 61.6% for PEG 4000 and Tween 80, respectively. Furthermore, the promoting mechanism of these surfactants on enzymatic hydrolysis was investigated by real-time surface plasmon resonance (SPR) and fluorescence spectroscopy. Results from SPR analysis showed that Tween 80 outperformed PEG 4000 in terms of dissociating the irreversible cellulase adsorption onto lignin. Fluorescence quenching mechanism revealed that PEG 4000 and Tween 80 intervened the interaction between lignin and cellulase by hydrogen bonds/Van der Waals and hydrophobic action, respectively. This work provided an in-depth understanding of the mechanisms of PEG 4000 and Tween 80 on enhancing the enzymatic hydrolysis efficiency.

Efficient removal of residual lignin from eucalyptus pulp via high-concentration chlorine dioxide treatment and its effect on the properties of residual solids

In fact, effectively removing lignin from pulp fibers facilitates the conversion and utilization of cellulose. In this study, the residual lignin in eucalyptus pulp was separated using a high concentration of chlorine dioxide. The effects of chlorine dioxide dosage, temperature, and time on lignin removal were investigated. The optimal conditions are chlorine dioxide dosage 5.0%, reaction temperature 40 °C, and reaction time 30 min. The lignin removal yield is 88.21%. The removal yields of cellulose and hemicellulose are 2.28 and 17.00%, respectively. The treated eucalyptus pulp has higher fiber crystallinity and thermal stability. The carbon content on the fiber surface is significantly reduced. The results show that lignin is removed by efficient oxidation, and the degradation of carbohydrates is inhibited using high concentrations of chlorine dioxide at low temperatures and short reaction times. This provides theoretical support for high value conversion of cellulose.

Customized Utilization Strategies of Industrial Lignin to Produce Adsorbents and Flocculants Based on Fractionation and Adequate Structural Interpretation

Lignin, a by-product of pulping and biorefinery, has great potential to replace petrochemical resources for wastewater purification. However, the defects of lignin, such as severe heterogeneity, inferior reactivity and poor solubility, characterize the production process of lignin-based products by high energy consumption and serious pollution. In this study, several lignin fractions with relatively homogeneous structure were first obtained by organic solvent fractionation, and their structures were fully deciphered by various characterization techniques. Subsequently, each lignin component was custom-valued for wastewater purification based on their structural characteristics. Benefiting from the high reactivity and reaction accessibility, the lignin fraction (lignin-1) refined by dissolving in ethanol and n-butanol could been used as a raw material to produce cationic lignin-based flocculant (LBF) in a copolymerization system using green, cheap and recyclable ethanol as solvent. The lignin fraction (lignin-2) extracted by methanol and dioxane showed low reactivity and high carbon content, which was used to produce lignin-based activated carbon (LAC) with phosphoric acid as activator. Moreover, the influences of synthetic factors on the purification capacity were discussed, and the LBF and LAC produced under the optimal conditions showed distinguished purification effect on kaolin suspension and heavy metal wastewater, respectively. Furthermore, the corresponding purification mechanism and external factors were also elaborated. It is believed that this cleaner production strategy is helpful for the valorization of lignin in wastewater resources.

Enhancing the potential production of bioethanol with bamboo by γ-valerolactone/water pretreatment

In this study, the effect of the γ-valerolactone (GVL)/H2O pretreatment system on bamboo (Neosinocalamus affinis) for enzymatic hydrolysis and ethanol fermentation was investigated. The performance characterization of the pretreated bamboo substrates, including the chemical composition, the structural characteristics, and the ability to produce bioethanol, were evaluated. The recovered substrates were enzymatically hydrolyzed for 48 h and then fermented to bioethanol. For the cellulose in the raw bamboo material, the highest cellulose-to-glucose conversion yield (CGCY) was achieved at 140 °C for 2 h with GVL : H2O = 8 : 2, which was 73.39%, and the cellulose-to-ethanol conversion yield (CECY) was 67.00%. This indicated that 183.5 kg of bioethanol could be produced per ton of bamboo, which was 9.71-folds higher than that directly converted from the untreated raw bamboo powder. Under these conditions, 50.60% of the active lignin can be recovered and be used as a wood-derived feedstock for further high-valued utilization. Meanwhile, the maximum concentration of fermentation inhibitors formed after pretreatment was about 140.9 mmol L-1, and had weak inhibition to the subsequent reaction. It has been shown that the cellulose could be effectively separated from bamboo and converted into bioethanol through the GVL/H2O pretreatment system.

Efficient fractionation of bamboo residue by autohydrolysis and deep eutectic solvents pretreatment

Bamboo processing residue, which is rich in parenchyma cells, was treated as huge waste in bamboo processing industry, such as reassemble bamboo and bamboo flooring. Herein, autohydrolysis and rapid different deep eutectic solvents (DES) delignification strategy were consecutively performed to remove hemicelluloses and lignin from bamboo processing residue. The xylooligosaccharides (XOS) with high yield (34.35%) was achieved in the autohydrolysis process. Results showed that alkaline DES pretreatment resulted in the highest glucose yield (88.22%) and relatively high delignification rate (83.75%) as well as well-preserved lignin structures. However, the lignin fractions obtained under acidic DES conditions were tending to assemble into lignin nanoparticles (LNPs) and having excellent antioxidant activity as compared to those obtained from alkaline DES system. In brief, the combination of autohydrolysis and rapid DES delignification can achieve orientated fractionation of the components from the industrialized bamboo.

Deciphering the linkage type and structural characteristics of the p-hydroxyphenyl unit in Pinus massoniana Lamb compressed wood lignin

To reveal the existence of p-hydroxyphenyl (H) units in compressed wood lignin, four different milled wood lignins were extracted using Pinus massoniana Lamb compressed wood, Pinus massoniana Lamb normal wood, and sugarcane bagasse as raw materials. Then, three dehydrogenation polymers (DHPs) were synthesized using coniferyl/p-coumaryl alcohol as raw materials to reveal the interunit linkages of H units. The lignin and DHP samples were systematically characterized by ¹H, ¹³C, 2D HSQC, and ³¹P NMR techniques. Compared with the opposite wood milled wood lignin (OW-MWL) and the normal wood milled wood lignin (NW-MWL), the compressed wood milled wood lignin (CW-MWL) contained a large amount of H units, and the H/G ratio and the p-hydroxyphenyl OH group contents were 0.15 and 1.09 mmol/g, respectively. Through the characterization of CW-MWL and DHPs, it was revealed that p-hydroxyphenyl units mainly coupled with other units by β-O-4, β-β, and β-5 linkages. Compared to the sugarcane bagasse milled wood lignin, it was clearly demonstrated that the H unit rather than p-coumarate ester occurred in CW-MWL. This study comprehensively explored the structural characteristics and linkages of H units in compress wood lignin, and provided useful information for revealing the participation of H units in the construction of lignin macromolecules.

Delignification efficiency of various types of biomass using microwave-assisted hydrotropic pretreatment

The use of a method of an effective delignification of lignocellulosic biomass is a key stage of designing processes of its microbiological conversion e.g. for the purposes of the production of cellulosic ethanol. The study was aimed at evaluating the effectiveness of microwave-assisted hydrotropic pretreatment using sodium cumene sulfonate (NaCS) for the delignification of pine and beech chips and wheat straw. Research results presenting the impact of process parameters of microwave-assisted hydrotropic delignification confirm a high effectiveness of this method of pretreatment of lignocellulosic biomass. The observed effects included changes in the composition of the biomass and an increased susceptibility of cellulose to the subsequent enzymatic hydrolysis. The use of microwave heating combined with an addition of hydrotrope of 40% w/v NaCS and 117 PSI for 60 min enabled a reduction of the absolute concentration of lignins by 36.58% in pine chips, by 57.68% in beech chips, and by 74.08% in wheat straw. After enzymatic hydrolysis was conducted, the highest concentration of glucose: 463.27 ± 11.25 mg glucose/g (hydrolysis yield 46.76 ± 1.14%) was obtained from the wheat straw, while 327.70 ± 22.15 mg glucose/g (hydrolysis yield 35.13 ± 2.37%) was acquired from the beech chips, and only 50.77 ± 0.75 mg glucose/g (hydrolysis yield 6.63 ± 0.10%) was obtained from the pine chips. Microwave-assisted hydrotropic delignification in the optimum process conditions additionally allows a complete removal of hemicellulose from biomass, which improves the effectiveness of enzymatic hydrolysis. Due to a significant reduction of lignin and hemicellulose concentration in biomass, cellulose—which is susceptible to enzymatic hydrolysis and a source of carbon in biosynthesis processes—becomes the main biomass component.

Integrated pretreatment of banana agrowastes: Structural characterization and enhancement of enzymatic hydrolysis of cellulose obtained from banana peduncle

An integrated treatment coupling alkali, steam explosion and ammonia/chlorine-free bleaching with sequential mild acid pretreatment were performed to isolate and characterize cellulose from banana agrowastes followed by optimized enzymatic hydrolysis to glucose. The cellulose yield, compositional, microstructural, and morphological analysis initially obtained from three post-harvest banana agrowastes (peel, pseudostem, and peduncle) were surveyed. Isolation parameters for banana peduncle agrowastes, the most efficient precursor, were reconfigured for acid hydrolysis by applying an orthogonal L₉ array of Taguchi design. Effects of solution-to-pulp ratio, acid concentration, temperature, and reaction time on physicochemical parameters were assessed resulting in ~81% cellulose recovery. Subsequently, cellulase driven enzymatic conversion to glucose was modelled using response surface methodology (RSM), where the mutual influences of incubation time, enzyme concentration, substrate concentration, and surfactant concentration were investigated. Artificial Neural Network (ANN) modelling further improved upon RSM optimizations ensuing ~97% optimized glucose yield, verified experimentally.

Co-production of xylooligosaccharides and glucose from birch sawdust by hot water pretreatment and enzymatic hydrolysis

A green method for co-production of value-added xylooligosaccharides (XOS) and glucose from birch was demonstrated using hot water pretreatment. Effects of pretreatment severity factor (Log R₀) on XOS production and enzymatic hydrolysis were investigated. At Log R₀ of 4.05 (180 °C, 50 min), the maximum hydrolysis yield (80.8%) was obtained. At Log R₀ of 3.91 (170 °C, 70 min), the maximum XOS yield (46.1%) was obtained, however the hydrolysis yield decreased to 70.3%. To achieve both the high XOS yield and high glucose output, Tween 80 addition (0.075 g/g cellulose) was employed, leading to an improvement in hydrolysis yield from 70.3% to 89.4%. From a mass balance perspective, 104.6 g of XOS and 372.9 g of glucose could be produced from 1000 g birch. These results demonstrated that birch sawdust is a promising lignocellulosic material for co-production of XOS and glucose.

Lignocellulose Degradation and Enzymatic Hydrolysis of Soybean Incorporated Sorghum Silage Inoculated with Feruloyl-Esterase Producing Lactobacillus plantarum

Availability of feedstock is one of the uncertainties impeding cellulosic biofuel production, and conservation of whole crop biomass as silage is a promising method to ensure year-round feedstock availability for biofuel production. This study investigated lignocellulose degradation and subsequent enzymatic hydrolysis of a 90-d sorghum silage incorporated with soybean and inoculated with Lactobacillus plantarum A1 in a three (0, 25, and 50%; soybean inclusions) by two (uninoculated and inoculated) factorial experiment. The results revealed that L. plantarum A1 inoculated silages had improved fermentation characteristics. The silages’ total N and non-fiber carbohydrate increased with L. plantarum A1 and soybean inclusion (p < 0.05). Inoculation also increased the residual water-soluble carbohydrate by 33.9% (p < 0.05). Inoculation and soybean inclusion significantly hydrolyzed the biomass’ lignocellulose, altered its morphology and microstructural matrix, increased production of ferulic acid and reduced the biomass crystallinity by 15.60% (p < 0.05). L. plantarum A1 inoculation × soybean inclusion improved glucose yield and cellulose conversion during enzymatic saccharification compared to uninoculated treatments. Therefore, incorporating soybean into sorghum silage with L. plantarum A1 inoculation enhanced fermentation quality, lignocellulose degradation and enzymatic saccharification which could serve as a sure way for sustainable year-round feedstock supply for enhanced biofuel production.

Recent advances of lignin valorization techniques toward sustainable aromatics and potential benchmarks to fossil refinery products

Aromatic compounds are important fuels and key chemical precursors for organic synthesis, however the current aromatics market are mainly relying on fossil resources which will eventually contribute to carbon emissions. Lignin has been recognized as a drop-in substitution to conventional aromatics, with its values gradually realized after tremendous research efforts in the recent five years. To facilitate the development of a possible lignin economics, this study overviewed the recent advances of various biorefinery techniques and the remaining challenging for lignin valorization. Starting with recent discovery of unexplored lignin structures, the potential functions of lignin related chemical structures were emphasized. The important breakthrough of lignin-first pretreatment, catalytic lignin depolymerization, and the high value products with possible benchmark with modern aromatics were reviewed with possible future targets. Possible retrofit of conventional petroleum refinery for lignin products were also introduced and hopefully paving a way to progressively migrate the industry towards carbon neutrality.

A review on recent developments in hydrodynamic cavitation and advanced oxidative processes for pretreatment of lignocellulosic materials

Environmental problems due to utilization of fossil-derived materials for energy and chemical generation has prompted the use of renewable alternative sources, such as lignocellulose biomass (LB). Indeed, the production of biomolecules and biofuels from LB is among the most important current research topics aiming to development a sustainable bioeconomy. Yet, the industrial use of LB is limited by the recalcitrance of biomass, which impairs the hydrolysis of the carbohydrate fractions. Hydrodynamic cavitation (HC) and Advanced Oxidative Processes (AOPs) has been proposed as innovative pretreatment strategies aiming to reduce process time and chemical inputs. Therefore, the underlying mechanisms, procedural strategies, influence on biomass structure, and research gaps were critically discussed in this review. The performed discussion can contribute to future developments, giving a wide overview of the main involved aspects.

Pretreatment Affects Profits From Xylanase During Enzymatic Saccharification of Corn Stover Through Changing the Interaction Between Lignin and Xylanase Protein

Effective pretreatment is vital to improve the biomass conversion efficiency, which often requires the addition of xylanase as an accessory enzyme to enhance enzymatic saccharification of corn stover. In this study, we investigated the effect of two sophisticated pretreatment methods including ammonium sulfite (AS) and steam explosion (SE) on the xylanase profits involved in enzymatic hydrolysis of corn stover. We further explored the interactions between lignin and xylanase Xyn10A protein. Our results showed that the conversion rates of glucan and xylan in corn stover by AS pretreatment were higher by Xyn10A supplementation than that by SE pretreatment. Compared with the lignin from SE pretreated corn stover, the lignin from AS pretreated corn stover had a lower Xyn10A initial adsorption velocity (13.56 vs. 10.89 mg g⁻¹ min⁻¹) and adsorption capacity (49.46 vs. 27.42 mg g⁻¹ of lignin) and weakened binding strength (310.6 vs. 215.9 L g⁻¹). Our study demonstrated the low absolute zeta potential and strong hydrophilicity of the lignin may partly account for relative weak interaction between xylanase protein and lignin from AS pretreated corn stover. In conclusion, our results suggested that AS pretreatment weakened the inhibition of lignin to enzyme, promoted the enzymatic hydrolysis of corn stover, and decreased the cost of enzyme in bioconversion.

Microwave Assisted Pretreatment of Szarvasi (Agropyron elongatum) Biomass to Enhance Enzymatic Saccharification and Direct Glucose Production

Biomass from perennial plants can be considered a carbon-neutral renewable resource. The tall wheatgrass hybrid Szarvasi-1 (Agropyron elongatum, hereafter referred to as "Szarvasi") belongs to the perennial Poaceae representing a species, which can grow on marginal soils and produce large amounts of biomass. Several conventional and advanced pretreatment methods have been developed to enhance the saccharification efficiency of plant biomass. Advanced pretreatment methods, such as microwave-assisted pretreatment methods are faster and use less energy compared to conventional pretreatment methods. In this study, we investigated the potential of Szarvasi biomass as a biorefinery feedstock. For this purpose, the lignocellulosic structure of Szarvasi biomass was investigated in detail. In addition, microwave-assisted pretreatments were applied to Szarvasi biomass using different reagents including weak acids and alkali. The produced pulp, hydrolysates, and extracted lignin were quantitatively characterized. In particular, the alkali pretreatment significantly enhanced the saccharification efficiency of the pulp 16-fold compared to untreated biomass of Szarvasi. The acid pretreatment directly converted 25% of the cellulose into glucose without the need of enzymatic digestion. In addition, based on lignin compositional and lignin linkage analysis a lignin chemical model structure present in Szarvasi biomass could be established.

Simultaneous Enzymatic Cellulose Hydrolysis and Product Separation in a Radial-Flow Membrane Bioreactor

Hydrolysis is the heart of the lignocellulose-to-bioethanol conversion process. Using enzymes to catalyze the hydrolysis represents a more environmentally friendly pathway compared to other techniques. However, for the process to be economically feasible, solving the product inhibition problem and enhancing enzyme reusability are essential. Prior research demonstrated that a flat-sheet membrane bioreactor (MBR), using an inverted dead-end filtration system, could achieve 86.7% glucose yield from purified cellulose in 6 h. In this study, the effectiveness of flat-sheet versus radial-flow MBR designs was assessed using real, complex lignocellulose biomass, namely date seeds (DSs). The tubular radial-flow MBR used here had more than a 10-fold higher membrane surface area than the flat-sheet MBR design. With simultaneous product separation using the flat-sheet inverted dead-end filtration MBR, a glucose yield of 10.8% from pretreated DSs was achieved within 8 h of reaction, which was three times higher than the yield without product separation, which was only 3.5% within the same time and under the same conditions. The superiority of the tubular radial-flow MBR to hydrolyze pretreated DSs was confirmed with a glucose yield of 60% within 8 h. The promising results obtained by the novel tubular MBR could pave the way for an economic lignocellulose-to-bioethanol process.

Investigation of hydrogen peroxide-acetic acid pretreatment to enhance the enzymatic digestibility of bamboo residues

Bamboo biomass was widely considered as a promising substitute for lignocellulose to produce fermentable sugars and biofuels in the south of China. When P. amarus were treated using hydrogen peroxide and acetic Acid pretreatment in the presence of sulphuric acid at 60 ℃ for 2 h, 82.63% lignin was removed from the bamboo residue, and enzymatic saccharification yield of 79.3% and ethanol content of 13.31 g/L were obtained. Analysis indicated that HPAC pretreatment increased the hydrophilic and porous nature of substrate, which can improve the enzyme accessibility to cellulose. When HPAC-pretreated D. sinicus, B. lapidea, N. affinis, andD. giganteus were used as the substrates of enzymatic saccharification, glucose yields of 71-84% at 72 h were achieved. HPAC pretreatment was a highly efficient and environmentally friendly method for bamboo biorefinery in the south of China.

Insights into alkaline choline chloride-based deep eutectic solvents pretreatment for Populus deltoides: Lignin structural features and modification mechanism

Deep eutectic solvent (DES) is a kind of green solvent for biorefinery, which favors the progress of being more environmentally friendly and effective. A better understanding of structural changes of lignin is necessary to optimize pretreatment conditions and efficient utilization of the resultant lignin. The current study reported the structural features of lignin recovered from alkaline ChCl/imidazole and ChCl/urea DES pretreatment, and the mechanism of lignin modification was revealed. The profiling demonstrated that lignin samples possessed a high purity (>94.4%), low molecular weight ranging from 1544 to 2562 g/mol and an excellent uniformity (PDI < 1.6). Noteworthy, the content of β-O-4' linkages in lignin was over 75% (i.e. 72.2%-77.4% retention); S/G ratio was increased whereas the content of -OCH₃ groups were decreased. It was revealed that slight cleavage of β-O-4' linkages, preferential breakdown of G units, and demethylation reaction were occurred during alkaline ChCl-based DES pretreatment. Specifically, cleavage of ester linkages between PB and lignin macromolecule was taking place during ChCl/imidazole pretreatment at a high temperature; whereas oxidation only appeared in ChCl/urea system. Despite the modification, well β-O-4' preserved and less condensed lignin samples were recovered after low-temperature pretreatment. Consequently, high contents of phenol derivatives (26.3-30.6%) were achieved in lignin oil. The present study provides critical information on alkaline ChCl-based DES pretreatment, which will contribute to the valorization of lignin by-products and will be beneficial to the development of biorefineries.

Properties of Multilayer Transparent Bamboo Materials

The objective of this study is to solve the shortcomings of the current transparent bamboo veneer with a small thickness and low light transmittance by means of lamination. The delignified bamboo templates were vacuum impregnated with an epoxy resin, and the impregnated bamboo templates were laminated with the same radial texture using the viscosity of the epoxy resin to obtain multilayer transparent bamboo (MLTB). The multilayer stacking method can greatly improve the optical and mechanical properties of transparent bamboo. The transparent bamboo with a thickness of 1.2 mm and the delignified bamboo with a volume fraction of 44.8% prepared by multilayer stacking exhibited an improved total optical transmissivity of up to 78.6%, while the highest transmittance of bamboo (0.9 mm thick) without multilayer stacking treatment was only 10.4%. Compared with the single-layer transparent bamboo with a thickness of 2.1 mm, the maximum tensile strength of the seven-layer transparent bamboo was 4 times that of the single-layer transparent bamboo. Therefore, MLTB can compensate to a certain extent for the low light transmission and poor mechanical properties of single-layer transparent bamboo. Overall, MLTB shows a richer and more layered texture, which has more esthetic value. It is a kind of natural transparent material with good light transmittance and excellent mechanical properties, which has a good development prospect as a structural material in the fields of construction, household, and electronic products.

Self-generated peroxyacetic acid in phosphoric acid plus hydrogen peroxide pretreatment mediated lignocellulose deconstruction and delignification

BACKGROUND

Peroxyacetic acid involved chemical pretreatment is effective in lignocellulose deconstruction and oxidation. However, these peroxyacetic acid are usually artificially added. Our previous work has shown that the newly developed PHP pretreatment (phosphoric acid plus hydrogen peroxide) is promising in lignocellulose biomass fractionation through an aggressive oxidation process, while the information about the synergistic effect between H3PO4 and H2O2 is quite lack, especially whether some strong oxidant intermediates is existed. In this work, we reported the PHP pretreatment system could self-generate peroxyacetic acid oxidant, which mediated the overall lignocellulose deconstruction, and hemicellulose/lignin degradation.

RESULTS

The PHP pretreatment profile on wheat straw and corn stalk were investigated. The pathways/mechanisms of peroxyacetic acid mediated-PHP pretreatment were elucidated through tracing the structural changes of each component. Results showed that hemicellulose was almost completely solubilized and removed, corresponding to about 87.0% cellulose recovery with high digestibility. Rather high degrees of delignification of 83.5% and 90.0% were achieved for wheat straw and corn stalk, respectively, with the aid of peroxyacetic acid oxidation. A clearly positive correlation was found between the concentration of peroxyacetic acid and the extent of lignocellulose deconstruction. Peroxyacetic acid was mainly self-generated through H2O2 oxidation of acetic acid that was produced from hemicellulose deacetylation and lignin degradation. The self-generated peroxyacetic acid then further contributed to lignocellulose deconstruction and delignification.

CONCLUSIONS

The synergistic effect of H3PO4 and H2O2 in the PHP solvent system could efficiently deconstruct wheat straw and corn stalk lignocellulose through an oxidation-mediated process. The main function of H3PO4 was to deconstruct biomass recalcitrance and degrade hemicellulose through acid hydrolysis, while the function of H2O2 was to facilitate the formation of peroxyacetic acid. Peroxyacetic acid with stronger oxidation ability was generated through the reaction between H2O2 and acetic acid, which was released from xylan and lignin oxidation/degradation. This work elucidated the generation and function of peroxyacetic acid in the PHP pretreatment system, and also provide useful information to tailor peroxide-involved pretreatment routes, especially at acidic conditions.

Effects of post-washing on pretreated biomass and hydrolysis of the mixture of acetic acid and sodium hydroxide pretreated biomass and their mixed filtrate

Effects of post-washing [one-volume water (I-VW) or double-volume water (Ⅱ-VW)] on pretreated hemp and poplar biomass and enzymatic hydrolysis of the mixture of HOAc and NaOH pretreated biomass and their mixed filtrate were investigated. Compared to I-VW, Ⅱ-VW increased 3.76-6.80% of glucan content in NaOH pretreated biomass, diminished lignin recondensation, and heightened cellulose-related FTIR peak intensities, crystallinity index, and lignin removal. The pH of mixed filtrate was around 4.80, precipitating the NaOH soluble lignin partially. Although Ⅱ-VW showed lower lignin recoveries than I-VW, their FTIR characteristics were equivalent to the commercial alkali lignin. Enzymatic hydrolysis at solid loadings of 2.5-10% (w/v) demonstrated that I-VW and Ⅱ-VW had marginal variations in sugar concentration and conversion efficiency, indicating that I-VW is sufficient for post-washing pretreated biomass. Glucose concentration exhibited a quadratic correlation with solid loading and hemp biomass reached the maximum glucose (43.88 g/L) and total sugar (57.08 g/L) concentrations with I-VW.

Revalorization of sunflower stalk pith as feedstock for the coproduction of pectin and glucose using a two-step dilute acid pretreatment process

BACKGROUND

Sunflower stalk pith, residue from the processing of sunflower, is rich in pectin and cellulose, thereby acting as an economic raw material for the acquisition of these compounds. In order to increase the commercial value of sunflower processing industry, a two-step dilute sulfuric acid treatment process was conducted on spent sunflower stalk pith to obtain the value-added products, pectin and glucose.

RESULTS

In this study, pectin was firstly extracted under mild acid condition to avoid pectin degradation, which was conducted at 90 °C with a pH of 2.0 for 2 h, and ~0.14 g/g of pectin could be recovered. Then the remaining solids after pectin extraction were subjected to the reinforced treatment process with 0.75% H₂SO₄ at 150 °C for 30 min to further improve enzymatic hydrolysis efficiency. Moreover, by combining a fed-batch enzymatic hydrolysis strategy, a solid loading content of 16% was successfully achieved and the glucose titer reached 103.1 g/L with a yield of 83.6%.

CONCLUSION

Finally, ~140 g pectin and 260 g glucose were produced from 1 kg of raw sunflower stalk pith using the integrated biorefinery process. This work puts forward a two-step dilute acid pretreatment combined with enzymatic hydrolysis method to produce pectin and glucose from sunflower spent waste.

Dissolution pretreatment of cellulose by using levulinic acid-based protic ionic liquids towards enhanced enzymatic hydrolysis

In this study, an economically competitive and sustainable levulinic acid-based protic ionic liquids were identified to be good solvents for the dissolution pretreatment of cellulose towards enhanced enzymatic hydrolysis. The influences of protic ionic liquids species, dissolution pretreatment time, and pretreatment temperature on the physico-chemical structures of cellulose were systematically investigated by various analytical techniques. The findings indicate that the pretreatment efficiency was correlated to the basicity of the organic bases, and the presence of ketone group in the levulinate anion with particular hydrogen bonding forming ability via keto-enol tautomerism. The DBN derived protic ionic liquids exhibited best performance at 100 °C in 1 h, as evidenced by a 94% glucose yield. This solvent system was also suitable for the dissolution pretreatment of corn stover-based lignocellulosic biomass for sugars production, although a higher temperature and longer pretreatment time was required. Furthermore, the solvent system could be recycled and reused.

Culturing rhodotorula glutinis in fermentation-friendly deep eutectic solvent extraction liquor of lignin for producing microbial lipid

Currently, deep eutectic solvents (DES) have attracted increasing attention due to their excellent performance in delignification. However, few studies focused on the treatment of DES waste liquid after extraction of lignin. In this work, the fermentation-friendly DES comprised of glycerol, choline chloride (ChCl) and acetic acid (AA) was applied for delignification of lignocellulose. Subsequently, the extraction effects of different DES were investigated, and the DES extraction liquor was used for lipid production. Results shows ChCl made little difference to lipid synthesis, while excessive AA exerted inhibitory effect on the growth of cells. Following pretreatment, the delignification exceeded 63%. When the DES liquid obtained after lignin extraction was used to produce lipid, the delay period was obvious, while the lipid yield and content were unaffected. Not only is the DES prepared in this study effective in delignification of lignocellulose, it is also applicable as raw material to produce lipid.

Benzenesulfonic acid-based hydrotropic system for achieving lignocellulose separation and utilization under mild conditions

Developing low-cost and sustainable fractionation technology is the key to achieve the maximal utilization of lignocellulosic biomass. This study reported benzenesulfonic acid (BA) as a green hydrotrope for efficient lignocellulose conversion into two fractions at atmospheric pressure: (1) a primarily cellulosic solid residue that can be utilized to produce high-value building blocks (lignocellulosic nanomaterials or sugars), and (2) the collected spent acid liquor that can be diluted with anti-solvent to easily obtain lignin nanoparticles. BA hydrotropic method exhibited greater reaction selectivity to solubilize lignin, where approximately 80% lignin were removed at only 80 °C in 20 min. The lower lignin content substrates resulted in relatively higher enzymatic hydrolysis efficiency of 80% and less entangled lignocellulosic nanofibrils (LCNF). Furthermore, the separated lignin particles size can be easily adjusted by the initial acid concentration. Overall, this work presented a promising and simple technology in achieving lignocellulose separation and utilization under mild conditions.

Factors Affecting the Catalytic Efficiency and Synergism of Xylanase and Cellulase During Enzymatic Hydrolysis of Birch Wood

Understanding factors that affect the catalytic efficiency and synergism of enzymes is helpful to enhance the process of bioconversion. In this study, birch wood (BW) was sequentially treated by delignification (DL), deacetylation (DA), and decrystallization (DC) treatments. The physiochemical structures of treated BW were characterized. Moreover, the influences of sequential treatments on the catalytic efficiency and synergism of xylanase and cellulase were studied. DL treatments efficiently improved the conversion of cellulose and xylan. A high degree of synergy (DS) between xylanase and cellulase was produced during hydrolysis of DL-treated BW. DA treatments enhanced xylan conversion but reduced the DS between xylanase and cellulase for xylan hydrolysis, whereas DC treatments enhanced cellulose conversion but reduced the DS between xylanase and cellulase for cellulose hydrolysis. The cellulose conversion of lithium chloride/N,N-dimethylacetamide (LiCl/DMAc)-treated BW (89.69%) was higher than the cellulose conversion of ball milling (BM)-treated BW (81.63%), whereas the xylan conversion of LiCl/DMAc-treated BW (83.77%) was lower than the xylan conversion of BM-treated BW (87.21%). This study showed that the catalytic efficiency and synergism of xylanase and cellulase are markedly affected by lignin hindrance, hemicellulose acetylation, and cellulose crystallization.

Preparing printable bacterial cellulose based gelatin gel to promote in vivo bone regeneration

The naturally tight entanglement of fibers in bacterial cellulose (BC) results in low printability when BC is used as a bioink for printing scaffolds. In this study, neat BC was treated by TEMPO-mediated oxidation (TO-BC) and maleic acid (MA-BC) to prepare homogeneous BC dispersions to fabricate scaffolds for bone regeneration. Results showed that the treatments released individual fibrils in the corresponding uniform dispersions without impairing inherent crystalline properties. Compared with TO-BC, MA-BC hybridized with gelatin could endow the gel with improved rheological properties and compression modulus for 3D printing. Both TO-BC and MA-BC dispersions showed good osteoblast viability. However, MA-BC possessed more pronounced ability to express osteogenic marker genes and formation of mineralized nodules in vitro. Compared with TO-BC-based gelatin scaffolds, MA-BC-based gelatin scaffolds showed a better ability to stimulate the regeneration of rat calvaria, demonstrating a higher bone mineral density of newly formed bone and trabecular thickness in vivo.

Sustainable preparation of cellulose nanofibrils via choline chloride-citric acid deep eutectic solvent pretreatment combined with high-pressure homogenization

Developing green and simple methods for the preparation of cellulose nanofibrils (CNFs) is of great significance. Herein, a green deep eutectic solvent (DES) system based on choline chloride (ChCl) and citric acid (CA) is employed to pretreat cellulose fibers for the preparation of CNFs. The effect of the pretreatment temperature on the chemo-physical properties of the CNFs is comprehensively investigated. A high CNFs yield of up to 84.19% can be achieved under optimized conditions. The optimal CNFs show a narrow diameter distribution and length up to several microns, high crystallinity and thermal stability, as well as excellent dispersibility in water. Furthermore, semi-transparent and flexible cellulose nanopaper (CNP) was fabricated through a facile vacuum filtration process. The optimal CNP shows high tensile strength (175.15 MPa) and toughness (7.51 MJ/m³). Therefore, this work provides a sustainable and facile approach to fabricate CNFs and CNP, which can be potentially used for various high-tech applications.

The effects of mild Lewis acids-catalyzed ethanol pretreatment on the structural variations of lignin and cellulose conversion in balsa wood

Ethanol organosolv pretreatment is a green and effective deconstruction process for main components in lignocellulose biomass. Herein, balsa wood was firstly subjected to a modified ethanol/water solution (EWS) pretreatment with different Lewis acids catalysts (AlCl₃, CuCl₂, FeCl₃) at 140-180 °C. The delignification ratios and structural characteristics of the dissociated lignin, enzymatic hydrolysis of cellulose in the pretreated substrates as well as the degradation products from hemicellulose during the pretreatment process were comprehensively investigated. Results showed that dissociation and depolymerization of lignin fragments was robust in AlCl₃-catalyzed pretreatment than those by CuCl₂ and FeCl₃-catalyzed pretreatment. In detail, the results showed that the optimal delignification ratio and removal of the hemicelluloses occurred in AlCl₃-catalyzed pretreatment. Moreover, the structural characterizations of lignin fractions by 2D-HSQC, ³¹P NMR and GPC also revealed that the obtained lignin has the advantages of small and homogeneous molecules as well as abundant functional groups. As a result of adequate removal of hemicellulose and lignin, the enzymatic digestibility of cellulose in the pretreated residue was significantly elevated. In short, the above findings are also in line with the concept of maximizing the utilization of bioresources, which will be beneficial for value-added applications of balsa wood in the biorefinery.

Sustainable preparation of bifunctional cellulose nanocrystals via mixed H2SO4/formic acid hydrolysis

In this work, a sustainable and highly efficient approach for preparing bifunctional cellulose nanocrystals (CNCs) was proposed through a mixed acid system of sulfuric acid and formic acid (FA). It was found that low-concentration (5-10 wt%) sulfuric acid can significantly improve the hydrolysis efficiency of FA (65-80 wt%), which enabled the highly efficient preparation of CNCs, i.e., the maximum yield of CNCs reached up to 70.65%. The obtained CNCs exhibited a rod-like shape with high crystallinity, and good dispersibility in both water and some organic phases. Moreover, the as-prepared CNCs exhibited high thermal stability, which is much higher than that of the traditionally sulfuric acid hydrolyzed ones. In addition, it was demonstrated that the bifunctional CNCs were able to stabilize various oils to form stable Pickering emulsion gels. Thus, this work provides a promising approach for sustainable preparation of bifunctional CNCs, which may find high-end applications in diverse fields.

Using the Major Components (Cellulose, Hemicellulose, and Lignin) of Phyllostachys praecox Bamboo Shoot as Dietary Fiber

Bamboo shoots are a renewable and abundant biomass containing cellulose, hemicellulose, and lignin. Although many studies have explored the applications of each of these components in the preparation of biochemicals and biopolymers, few studies have evaluated the utility of these components as a dietary fiber supplement. In this study, a powder consisting of the main components of bamboo shoots (cellulose, hemicellulose, and lignin) was prepared from fresh Phyllostachys praecox shoots and characterized by scanning electron microscopy, infrared spectroscopy, and X-ray diffraction. To evaluate the potential utility of these components as a dietary fiber supplement, we conducted an experiment in which this powder was supplemented in the diet of mice for 7 weeks. The experiment included three diet groups (n = 10/group): a low-fat control diet (LFC), high-fat diet (HFD), and high-fat diet with bamboo shoot powder (HFBSP). Compared with HFD mice, the body weights of LFC and HFBSP mice were lower, indicating that the addition of bamboo shoot powder could reduce the weight gain associated with the HFD. Bamboo shoot powder supplementation could also reduce the levels of triglycerides (TG), blood glucose (GLU), total cholesterol (CHOL), high-density lipoprotein (HDL-C), and low-density lipoprotein (LDL-C) in HFD mice. The fat histology images indicated that obesity was alleviated in HFBSP mice, and the liver histology images indicated that the addition of bamboo shoot powder to the HFD could reduce the risk of fatty liver disease. The addition of bamboo shoot powder to the HFD might also improve the gut microbiota of mice. Thus, the major components of bamboo shoot powder (cellulose, hemicellulose, and lignin) could be used as beneficial natural additives in the food industry.

Valorization of Enzymatic Hydrolysis Residues from Corncob into Lignin-Containing Cellulose Nanofibrils and Lignin Nanoparticles

As a kind of biomass waste, enzymatic hydrolysis residues (EHRs) are conventionally burned or just discarded, resulting in environmental pollution and low economic benefits. In this study, EHRs of corncob residues (CCR) were used to produce high lignin-containing cellulose nanofibrils (LCNFs) and lignin nanoparticles (LNPs) through a facile approach. The LCNFs and LNPs with controllable chemical compositions and properties were produced by tuning the enzymolysis time of CCR and the followed homogenization. The morphology, thermal stability, chemical and crystalline structure, and dispersibility of the resultant LCNFs and LNPs were further comprehensively investigated. This work not only promotes the production of lignocellulose-based nanomaterials but also provides a promising utilization pathway for EHRs.

An integrated biorefinery process for co-production of xylose and glucose using maleic acid as efficient catalyst

This study aims to valorize wheat straw for xylose and glucose recovery using maleic acid in the pretreatment. The process conditions of maleic acid hydrolysis of wheat straw for xylose recovery were optimized by response surface methodology, through which the maximum xylose recovery of 77.12% versus minimum furfural yield of 1.61% were achieved using 70 g/L solid-to-liquid ratio and 0.1 mol/L maleic acid for 40 min at 150 °C. Moreover, 88.58% cellulose conversion was achieved by enzymatic hydrolysis of maleic acid-pretreated wheat straw. Results showed that maleic acid was an effective pretreatment solvent for sugars recovery: 19.88 g xylose and 30.89 g glucose were respectively obtained from 100 g wheat straw due to acidic and enzymatic hydrolysis, with only 0.37 g furfural produced. This study provides a strategy for hydrolyzing wheat straw to produce fermentable sugars with low amount of degradation product.

Enhancing the enzymatic digestibility of bamboo residues by biphasic phenoxyethanol-acid pretreatment

The high content of lignin in bamboo is considered as the major obstacle for its biorefining. In this work, a green, lignin-selective, and recyclable solvent of phenoxyethanol was coupled with acid solution to deconstruct recalcitrant structure of bamboo residues (BR) to boost its enzymatic digestibility. Results showed phenoxyethanol has excellent lignin-removal ability from 29.4% to 91.6% when phenoxyethanol:acid ratios increased from 0:1 to 4:1 at 120 °C. 82.5%-87.8% of cellulose was preserved in pretreated BR. The enzymatic digestibility of BR significantly improved from 20.0% to 91.3% when it was pretreated under optimized conditions. With lower enzyme dosages (10 FPU/g) and 5 recycled using of pretreatment liquor, pretreated BR still showed a good enzymatic digestibility of 67.4%-93.7% and 67.1-76.8%, respectively. Examination of physicochemical changes revealed that improvements to accessibility, reduction of crystallite size, decrease of surface lignin and hydrophobicity for pretreated BR showed positive correlations (R² > 0.7) with their enzymatic digestibility.

Evaluation of the Dimensional Stability of Black Poplar Wood Modified Thermally in Nitrogen Atmosphere

Black poplar (Populus nigra L.) was thermally modified in nitrogen atmosphere. The effects of the modification process on poplar wood were evaluated for temperatures: 160 °C, 190 °C, and 220 °C applied for 2 h; and 160 °C and 190 °C for 6 h. The percentual impact of temperature and time of modification on the properties of modified wood was analysed. The study permitted the identification correlations between the chemical composition and selected physical properties of thermally modified poplar wood. The dimensional stability of poplar wood was improved after thermal modification in nitrogen. The higher the temperature of modification, the lower the equilibrium moisture content (EMC) of black poplar. At the temperature of 220 °C, EMC was two times lower than the EMC of non-modified black poplar. It is also possible to reduce the dimensional changes of wood two-fold (at the modification temperature of 220 °C), both in radial and tangential directions, independently of the acclimatization conditions (from 34% to 98% relative humidity, RH). Similar correlations have been found for wood that has been soaked in water. Higher modification temperatures and longer processing times contributed to a lower swelling anisotropy (SA).

The Investigation of TiO2 NPs Effect as a Wastewater Treatment to Mitigate Cd Negative Impact on Bamboo Growth

The recent emerging evidence reveals that titanium dioxide nanoparticles (TiO2 NPs) can be used as a wastewater treatment. This study provides new information about the possible detoxification role of TiO2 NPs as a wastewater treatment in plants under heavy metal stress, with an emphasis on the mechanisms involved. Here, we investigated the effects of TiO2 NPs as one wastewater treatment on a bamboo species (Arundinaria pygmaea L.) under in vitro Cadmium (Cd) toxicity conditions. A factorial experiment was conducted in a completely randomized design with four replications of four concentrations of Cd (50, 100, 200, and 300 µM) alone and in combination with 100 and 200 µM TiO2 NPs as two wastewater treatments, as well as a control treatment. The results indicated that TiO2 NPs concentrations enhanced enzymatic and non-enzymatic antioxidant activities and proline accumulation as well as reducing hydrogen peroxide (H2O2), superoxide radical (O2•−), and malondialdehyde (MDA) levels, which led to improved photosynthetic parameters with an eventual increase in plant biomass as compared to the control treatment. Therefore, TiO2 NPs improved the photosynthetic parameters of bamboo under Cd toxicity, which led to an increase in plant biomass. We concluded that the wastewater treatments of TiO2 NPs improved bamboo biomass through the scavenging of reactive oxygen species (ROS) compounds (H2O2 and O2•−), which was induced by the stimulation of the antioxidant capacity of the plant. TiO2 also protected cell membranes by reducing lipoperoxidation in bamboo under Cd toxicity. The concentration of 200 µM TiO2 NPs had the most impact in reducing Cd toxicity.