Efficient extraction of bagasse hemicelluloses and characterization of solid remainder

Mild three-stage alkali-oxygen treatment preserving the native macromolecular structure of lignin for effective disassembling of tobacco stalk

Tobacco stalks, as one of the annual economic crops rich in biomacromolecules such as cellulose and hemicellulose, are more difficult to decompose into cellulose fibers due to their high degree of lignification compared to other ordinary straw feedstocks, resulting in their underutilization. In this study, we developed a mild three-stage alkali‑oxygen (AO) process to efficiently deconstruct the tobacco stalk cell walls. The process, involving alkaline dosages of 15 %, 10 %, and 3 % at each stage, effectively dissociated the cell walls and yielded cellulose fibers with high brightness (42.0 % ISO). The organics in the spent liquor, including lignin, hemicellulose, and small-molecular extracts, were isolated through acid/ethanol precipitation and organic solvent extraction. Lignin characterization by 2D HSQC NMR indicated that the majority of native β-aryl ether linkages were preserved after AO treatment, making it suitable for producing chemicals or biofuels via depolymerization. Additionally, the small-molecular extracts contained numerous depolymerized products from lignin and carbohydrates, as well as bioactive compounds derived from the tobacco stalk. Overall, this mild, efficient, and eco-friendly process offers a promising approach for the valorization of tobacco stalks and similar biomass resources.

Xylitol production from passion fruit peel hydrolysate: Optimization of hydrolysis and fermentation processes

The passion fruit peel (PFP) has a high cellulose and hemicellulose content, which can be used to produce fermentable sugars. In this context, this study aims to optimize the release of xylose and the production of xylitol from PFP. The optimized conditions were 0.71 M dilute sulfuric acid and a 21.84-minute treatment, yielding 19.03 g/L of xylose (PFP-1). Different PFP hydrolysates were evaluated to improve xylitol production by the yeast Kluyveromyces marxianus ATCC 36907: PFP-2 (PFP1 treated with Ca(OH)2), PFP-3 (PFP-1 treated with Ca(OH)2 and activated carbon), PFP-4 (PFP-3 with biological elimination of glucose with S. cerevisiae, and concentrated at different xylose concentrations). The applied methods resulted in higher xylitol production (14.97 g/L), when PFP hydrolysate was detoxified with Ca(OH)2, treated with activated charcoal for 1 h, biotreated for glucose removal, and concentrated to 40 g/L of xylose.

Recent Advances in Superabsorbent Hydrogels Derived from Agro Waste Materials for Sustainable Agriculture: A Review

Superabsorbent hydrogels made from agro waste materials have the potential to promote sustainable agriculture and environmental sustainability. These hydrogels not only help reduce water consumption and increase crop yields but also contribute to minimizing waste and lowering greenhouse gas emissions. Recent research on superabsorbent hydrogels derived from agro wastes has focused on the preparation of hydrogels based on natural polymers isolated from agro wastes, such as cellulose, hemicellulose, and lignin. This review provides an in-depth examination of hydrogels developed from raw agro waste materials and natural polymers extracted from agro wastes, highlighting that these studies start with raw wastes as the main materials. The utilization strategies for specific types of agro wastes are comprehensively described. This review outlines different methods utilized in the production of these hydrogels, including physical cross-linking techniques such as dissolution-regeneration and freeze-thawing, as well as chemical cross-linking methods involving various cross-linking agents and graft polymerization techniques such as free radical polymerization, microwave-assisted polymerization, and γ radiation graft polymerization. Specifically, this review explores the applications of agro waste-based superabsorbent hydrogels in enhancing soil properties such as water retention and slow-release of fertilizers for sustainable agriculture.

Composition of Lignocellulose Hydrolysate in Different Biorefinery Strategies: Nutrients and Inhibitors

The hydrolysis and biotransformation of lignocellulose, i.e., biorefinery, can provide human beings with biofuels, bio-based chemicals, and materials, and is an important technology to solve the fossil energy crisis and promote global sustainable development. Biorefinery involves steps such as pretreatment, saccharification, and fermentation, and researchers have developed a variety of biorefinery strategies to optimize the process and reduce process costs in recent years. Lignocellulosic hydrolysates are platforms that connect the saccharification process and downstream fermentation. The hydrolysate composition is closely related to biomass raw materials, the pretreatment process, and the choice of biorefining strategies, and provides not only nutrients but also possible inhibitors for downstream fermentation. In this review, we summarized the effects of each stage of lignocellulosic biorefinery on nutrients and possible inhibitors, analyzed the huge differences in nutrient retention and inhibitor generation among various biorefinery strategies, and emphasized that all steps in lignocellulose biorefinery need to be considered comprehensively to achieve maximum nutrient retention and optimal control of inhibitors at low cost, to provide a reference for the development of biomass energy and chemicals.

Lignocellulosic biomass fertilizers: Production, characterization, and agri-applications

The growing focus on sustainable agriculture and optimal resource utilization has spurred investigations into lignocellulosic biomass as a potential source for producing environmentally friendly fertilizers. This paper reviews recent advancements in the production and application of innovative fertilizers derived from lignocellulose. It highlights potential in enhancing agricultural productivity and reducing environmental impacts such as carbon footprint and water pollution. The paper outlines various methods for conversion, highlighting the unique advantages of chemical, enzymatic, and microbiological processes, for converting lignocellulosic biomass into nutrient-rich fertilizers. The study compares the efficacy of lignocellulosic fertilizers to traditional fertilizers in promoting crop growth, enhancing soil health, and reducing nutrient losses. The results demonstrate the potential of lignocellulosic biomass-derived fertilizers in promoting resource efficiency and sustainable agriculture. While this research significantly contributes to the existing body of knowledge, further studies on long-term impacts and scalability are recommended for the development of innovative and sustainable agricultural practices.

Selective separation of hemicellulose from poplar by hydrothermal pretreatment with ferric chloride and pH buffer

As an environmentally friendly lignocellulosic biomass separation technology, hydrothermal pretreatment (HP) has a strong application prospect. However, the low separation efficiency is a main factor limiting its application. In this study, the poplar components were separated using HP with ferric chloride and pH buffer (HFB). The optimal conditions were ferric chloride concentration of 0.10 M, reaction temperature of 150 °C, reaction time of 15 min and pH 1.9. The separation of hemicellulose was increased 34.03 % to 77.02 %. The pH buffering resulted in the highest cellulose and lignin retention yields compared to ferric chloride pretreatment (FC). The high efficiency separation of hemicellulose via HFB pretreatment inhibited the degradation of xylose. The hydrolysate was effectively reused for five times. The fiber crystallinity index reached 60.05 %, and the highest C/O ratio was obtained. The results provide theoretical support for improving the efficiency of HP and promoting its application.

Differentiated Fractionation of Various Biomass Resources by p-Toluenesulfonic Acid at Mild Conditions

Biomass is the ideal substitute for petrochemical resources because of its renewable and abundant sources. p-Toluenesulfonic acid (p-TsOH) can effectively separate lignin from biomass under mild conditions, so it is highly expected in biomass fractionation to improve the utilization efficiency. In this study, we investigated the effect of p-TsOH differentiated fractionation of poplar sawdust, eucalyptus sawdust, and rice straw below 100 °C. According to the experimental results, upon pretreatment by p-TsOH of the three kinds of raw biomass, most of the lignin and hemicellulose of poplar sawdust and eucalyptus sawdust were removed, whereas the cellulose was retained, but most of the hemicellulose and cellulose of rice straw were kept, whereas the lignin was removed at similar conditions. The structures and compositions of pretreatment residues, lignin, and hemicellulose extracted from raw biomass were characterized by XRD, FTIR, HSQC-NMR, XPS, and SEM. The differentiated fractionation mechanism of biomass was analyzed. A better recognition and understanding of the factors affecting biomatrix opening and fractionation will allow for the identification of new pretreatment strategies that improve biomass utilization and permit the rational enzymatic hydrolysis of cellulose.

Encapsulation of Polyphenolic Compounds Based on Hemicelluloses to Enhance Treatment of Inflammatory Bowel Diseases and Colorectal Cancer

Inflammatory bowel diseases (IBD) and colorectal cancer (CRC) are difficult to cure, and available treatment is associated with troubling side effects. In addition, current therapies have limited efficacy and are characterized by high costs, and a large segment of the IBD and CRC patients are refractive to the treatment. Moreover, presently used anti-IBD therapies in the clinics are primarily aimed on the symptomatic control. That is why new agents with therapeutic potential against IBD and CRC are required. Currently, polyphenols have received great attention in the pharmaceutical industry and in medicine due to their health-promoting properties. They may exert anti-inflammatory, anti-oxidative, and anti-cancer activity, via inhibiting production of pro-inflammatory cytokines and enzymes or factors associated with carcinogenesis (e.g., matrix metalloproteinases, vascular endothelial growth factor), suggesting they may have therapeutic potential against IBD and CRC. However, their use is limited under both processing conditions or gastrointestinal interactions, reducing their stability and hence their bioaccessibility and bioavailability. Therefore, there is a need for more effective carriers that could be used for encapsulation of polyphenolic compounds. In recent years, natural polysaccharides have been proposed for creating carriers used in the synthesis of polyphenol encapsulates. Among these, hemicelluloses are particularly noteworthy, being characterized by good biocompatibility, biodegradation, low immunogenicity, and pro-health activity. They may also demonstrate synergy with the polyphenol payload. This review discusses the utility and potential of hemicellulose-based encapsulations of polyphenols as support for treatment of IBD and CRC.

Pretreatment of poplar with eco-friendly levulinic acid to achieve efficient utilization of biomass

Organic acid pretreatment is an effective method for green separation of lignocellulosic biomass. However, repolymerization of lignin seriously affects the dissolution of hemicellulose and the conversion of cellulose during organic acid pretreatment. Therefore, a new organic acid pretreatment, levulinic acid (Lev) pretreatment, was studied for the deconstruction of lignocellulosic biomass without adding additional additives. The preferred separation of hemicellulose was realized at Lev concentration 7.0%, temperature 170 °C, and time 100 min. The separation of hemicellulose increased from 58.38% to 82.05% compared with acetic acid pretreatment. It was found that the repolymerization of lignin was effectively inhibited in the efficient separation of hemicellulose. This was attributed to the fact that γ-valerolactone (GVL) is a good green scavenger of lignin fragments. The lignin fragments in the hydrolysate were effectively dissolved. The results provided theoretical support for creating green and efficient organic acid pretreatment and effectively inhibiting lignin repolymerization.

Enhancement of separation selectivity of hemicellulose from bamboo using freeze-thaw-assisted p-toluenesulfonic acid treatment at low acid concentration and high temperature

The cellulose-rich residual solids are obtained with p-toluenesulfonic acid (p-TsOH) treatment. However, better fractionation of hemicellulose and separation is difficult to obtain during treatment. This study aims at investigating the separation selectivity of bamboo hemicellulose using freeze-thaw-assisted p-TsOH (F/p-TsOH) treatment. The desired separation effect was achieved at freezing temperature -40 °C, freezing time 20 h, p-TsOH concentration 3.0 %, treatment temperature 130 °C and time 80 min. 93.26 % hemicellulose separation was found, which was 32.88 % higher than that of conventional p-TsOH treatment. Furthermore, the separation yield of lignin decreased significantly from 69.29 % to 13.98 %. The distinct lignin characteristic absorption peaks were found, while that of hemicellulose was difficult to observe. The fiber crystallinity index increased from 50.42 to 56.55 %. Furthermore, greater selectivity for hemicellulose separation was achieved. The results provide a new research thinking for efficient fractionation of lignocellulosic biomass by organic acid treatment.

High-efficiency separation of hemicellulose from bamboo by one-step freeze-thaw-assisted alkali treatment

The selectivity of alkali treatment (AT) for hemicellulose separation is reduced due to the alkali solubility of lignin. It was improved using freeze-thaw-assisted alkaline treatment (FT/AT). In this study, bamboo hemicellulose was separated via a one-step freeze-thaw-assisted alkali treatment (OFT/AT). The effects of freezing temperature, freezing time, alkali concentration, and treatment time on bamboo components were studied. The separation yield of hemicellulose was 73.26%, compared to 64.00% using conventional FT/AT. The separation of lignin and cellulose was inhibited as alkali concentration decreased from 7.0% to 5.0%. The extraction yield of hemicellulose increased from 46.35% to 56.12%. Structural analysis of extracted hemicellulose revealed the effective inhibition of the breakage of the xylose backbone and arabinose side chain of hemicellulose. This indicated that the molecular structure of extracted hemicellulose was relatively complete. It provides theoretical support for the efficient separation of hemicellulose by AT.

Enhancing for Bagasse Enzymolysis via Intercrystalline Swelling of Cellulose Combined with Hydrolysis and Oxidation

To overcome the biological barriers formed by the lignin–carbohydrate complex for releasing fermentable sugars from cellulose by enzymolysis is both imperative and challenging. In this study, a strategy of intergranular swelling of cellulose combined with hydrolysis and oxidation was demonstrated. Pretreatment of the bagasse was evaluated by one bath treatment with phosphoric acid and hydrogen peroxide. The chemical composition, specific surface area (SSA), and pore size of bagasse before and after pretreatment were investigated, while the experiments on the adsorption equilibrium of cellulose to cellulase and reagent reuse were also performed. Scanning electron microscopy (SEM) and high-performance liquid chromatography (HPLC) were employed for microscopic morphology observations and glucose analysis, respectively. The results showed that pretreated bagasse was deconstructed into cellulose with a nanofibril network, most of the hemicellulose (~100%) and lignin (~98%) were removed, and the SSA and void were enlarged 11- and 5-fold, respectively. This simple, mild preprocessing method enhanced cellulose accessibility and reduced the biological barrier of the noncellulose component to improve the subsequent enzymolysis with a high glucose recovery (98.60%).

High-Efficiency and High-Quality Extraction of Hemicellulose of Bamboo by Freeze-Thaw Assisted Two-Step Alkali Treatment

Hemicellulose is a major component of the complex biomass recalcitrance structure of fiber cell walls. Even though biomass recalcitrance protects plants, it affects the effective utilization of lignocellulosic biomass resources. Therefore, the separation and extraction of hemicellulose is very important. In this study, an improved two-step alkali pretreatment method was proposed to separate hemicellulose efficiently. Firstly, 16.61% hemicellulose was extracted from bamboo by the weak alkali treatment. Then, the physical freezing and the alkali treatment were carried out by freezing at -20 °C for 12.0 h and thawing at room temperature, heating to 80 °C, and treating with 5.0% sodium hydroxide for 90 min; the extraction yield of hemicellulose reached 73.93%. The total extraction yield of the two steps was 90.54%, and the molecular weight and purity reached 44,865 g·mol-1 and 89.60%, respectively. It provides a new method for breaking the biomass recalcitrance of wood fiber resources and effectively extracting hemicellulose.

Efficient separation of bagasse lignin by freeze-thaw-assisted p-toluenesulfonic acid pretreatment

Lignin separation is an important procedure that benefits multiple industries and in particular biomass transformation efforts. In this study, bagasse lignin was separated by freeze-thaw-assisted p-toluenesulfonic acid (p-TsOH) pretreatment. The optimal conditions were freezing temperature -60 °C, freezing time 8.0 h, thawing temperature 15 °C, p-TsOH concentration 60%, pretreatment temperature 70 °C, and time 20 min. Lower acid concentrations and temperatures were used compared with traditional p-TsOH pretreatment. The efficiency and selectivity of lignin separation were improved. It was attributed to freeze-thawing, which provided a more efficient physical channel for the effective penetration of p-TsOH. The separation, extraction and purity of lignin were improved to 89.76%, 78.22% and 77.89%, respectively. High separation, high extraction, high purity and large molecular weight lignin samples were obtained. In addition, the recovery and reuse of p-TsOH was enhanced. This provided a new method for the efficient and clean separation of lignin.

Optimization of Demineralization and Pyrolysis Performance of Eucalyptus Hydrothermal Pretreatment

The preparation of bio-oil through biomass pyrolysis is promoted by different demineralization processes to remove alkali and alkaline earth metal elements (AAEMs). In this study, the hydrothermal pretreatment demineralization was optimized by the response surface method. The pretreatment temperature, time and pH were the response elements, and the total dissolution rates of potassium, calcium and magnesium were the response values. The interactions of response factors for AAEMs removal were analyzed. The interaction between temperature and time was significant. The optimal AAEMs removal process was obtained with a reaction temperature of 172.98 °C, time of 59.77 min, and pH of 3.01. The optimal dissolution rate of AAEMs was 47.59%. The thermal stability of eucalyptus with and without pretreatment was analyzed by TGA. The hydrothermal pretreatment samples exhibit higher thermostability. The composition and distribution of pyrolysis products of different samples were analyzed by Py-GC/MS. The results showed that the content of sugars and high-quality bio-oil (C6, C7, C8 and C9) were 60.74% and 80.99%, respectively, by hydrothermal pretreatment. These results show that the removal of AAEMs through hydrothermal pretreatment not only improves the yield of bio-oil, but also improves the quality of bio-oil and promotes an upgrade in the quality of bio-oil.

Effect of temperature on simultaneous separation and extraction of hemicellulose using p-toluenesulfonic acid treatment at atmospheric pressure

Hemicelluloses were effectively separated using p-toluenesulfonic acid (p-TsOH) treatment at high temperature. High temperature and pressure promoted hydrolysis of hemicellulose, which limited its value upon recovery. In this study, bagasse hemicellulose was separated and extracted by p-TsOH treatment at atmospheric pressure. The effects of temperature, p-TsOH concentration, and time on hemicellulose separation and extraction were investigated. The optimal conditions were 80 °C, 3.0% p-TsOH, and 120 min. The separation and extraction yield of hemicellulose was 73.23% and 36.02%, respectively. Extraction hemicellulose with 95.60% purity was obtained. In addition, the dissolution mechanism of hemicellulose was analyzed. Degradation of β-glycosidic bonds was inhibited. Benzyl ether bond between carbohydrates and lignin was selectively cleaved. The skeleton structure of xylan in hemicellulose was protected while the functional groups of branch chain were severely damaged. It provides a valuable theoretical basis for the efficient separation and extraction of hemicellulose.

Preparation of hemicellulose-based hydrogels from biomass refining industrial effluent for effective removal of methylene blue dye

Cold caustic extraction (i.e. CCE) is an essential technique for removing hemicellulose from paper-grade pulp and thus obtaining high-purity dissolving pulp in pulp and paper industry. The generated wastewater from the CCE process contains large amounts of valuable hemicellulose which should be properly treated in a cost-effective way. Therefore, in this research, the hemicellulose has been used as a raw material for preparing hemicellulose-graft-polyacrylamide (hemi-g-pAAm) hydrogel particles for efficiently adsorbing methylene blue (MB) from aqueous solutions. The mass transfer kinetic behaviours of hemicellulose during a multiple CCE process were also studied. The MB adsorption kinetic test results showed that the removal efficiency can be higher than 90% for the simulated wastewater containing 500 mg/L of MB. Of note, the maximum removal capacities for the wastewater samples containing 500 and 1000 mg/L of MB could be reached up to ∼1800 and ∼2300 (mg/g) respectively with the equilibrium time of ∼40 min. Compared to other reported materials, the superior adsorption performance of the prepared hemicellulose-based hydrogel proved its great potential for application in the wastewater treatment of dye industry.

High efficiency and clean separation of eucalyptus components by glycolic acid pretreatment

Glycolic acid has chemical properties similar to those of formic acid. Therefore, similar to formic acid pretreatment, glycolic acid pretreatment has the separation effect of hemicellulose. In this study, eucalyptus hemicellulose was effectively separated by glycolic acid pretreatment. The effects of glycolic acid concentration, temperature and time on the separation of cellulose, hemicellulose and lignin were investigated. The optimum conditions were acid concentration 5.40%, temperature 140 °C, time 3.0 h. The highest yield of xylose was 56.72%. The recovery rate of glycolic acid was 91%. Compared to formic acid, the yield of xylose increased to 10.33% while that of lignin decreased to 11.08%. It showed high selectivity for hemicellulose separation, yielding 65.48% hemicellulose with 72.08% purity. The depolymerization and repolymerization of lignin were inhibited. The integrity of the cellulose structure was preserved. It provides theoretical support for the fractional separation and high-value transformation of lignocellulosic biomass.

Mechanically Strong, Low Thermal Conductivity and Improved Thermal Stability Polyvinyl Alcohol-Graphene-Nanocellulose Aerogel

Porous aerogel materials have advantages of a low density, low thermal conductivity and high porosity, and they have broad application prospects in heat insulation and building energy conservation. However, aerogel materials usually exhibit poor mechanical properties. Single-component aerogels are less likely to possess a good thermal stability and mechanical properties. It is necessary to prepare multiple-composite aerogels by reinforcement to meet practical application needs. In this experiment, a simple preparation method for polyvinyl alcohol (PVA)–graphene (GA)–nanocellulose (CNF) ternary composite aerogels was proposed. This is also the first time to prepare ternary composite aerogels by mixing graphene, nanocellulose and polyvinyl alcohol. A GA–CNF hydrogel was prepared by a one-step hydrothermal method, and soaked in PVA solution for 48 h to obtain a PVA–GA–CNF hydrogel. PVA–GA–CNF aerogels were prepared by freeze drying. The ternary composite aerogel has advantages of excellent mechanical properties, a low thermal conductivity and an improved thermal stability, because strong hydrogen bonds form between the PVA, GA and CNF. The composite aerogels were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, Brunauer–Emmett–Teller analysis, dynamic thermal analysis, thermogravimetry and thermal constant analysis to characterize the properties of the ternary composite aerogels. The lightweight, low-density and porous PVA–GA–CNF composite aerogels withstood 628 times their mass. The thermal conductivity of the composite aerogels was 0.044 ± 0.005 W/mK at room temperature and 0.045 ± 0.005 W/mK at 70 °C. This solid, low thermal conductivity and good thermal stability PVA–GA–CNF ternary composite aerogel has potential application in thermal insulation.

Ultralight, High Capacitance, Mechanically Strong Graphene-Cellulose Aerogels

With increasing energy demand driving the need for eco-friendly and efficient energy storage technology, supercapacitors are becoming increasingly prevalent in wearable devices because of their portability and stability. The performance of these supercapacitors is highly dependent on the choice of electrode material. The high capacitance and mechanical properties needed for these materials can be achieved by combining graphene's stable electrical properties with renewable cellulose's excellent mechanical properties into porous aerogels. In this study, graphene-cellulose hydrogels were prepared by a one-step hydrothermal method, with porous, ultra-light, and mechanically strong graphene-cellulose aerogels then prepared by freeze-drying. These composite aerogels possess excellent mechanical strength and high specific capacitance, capable of bearing about 1095 times the pressure of their own weight. Electrochemical tests show the specific capacitance of these composite aerogels can reach 202 F/g at a scanning rate of 5 mA/cm2. In view of their high surface area and fast charge transport provided by their 3D porous structure, graphene-cellulose aerogels have great potential as sustainable supercapacitor electrodes.

Green, efficient extraction of bamboo hemicellulose using freeze-thaw assisted alkali treatment

The premise of high value utilization of lignocellulosic biomass is effective separation of hemicellulose. In this paper, the extraction of bamboo hemicellulose using freeze-thaw assisted alkali treatment (FAT) was studied. The effect of alkali concentration, alkali treatment time, freezing temperature, and freeze-thaw time on the main components was studied. Bamboo was frozen at -30 °C for 12 h, thawed at room temperature, and then treated at 75 °C for 90 min with 7.0% alkali. The extraction rate of hemicellulose was as high as 64.71%. The purity of hemicellulose samples using conventional AT decreased from 82.63% to 78.56%. Hemicellulose with the same yield as that of conventional alkali treatment was obtained by further reducing the alkali concentration. The purity of hemicellulose samples increased from 82.63% to 89.45%. It had a higher purity, higher molecular weight, and lower polydispersity. A new, green and efficient alkaline extraction method for hemicellulose was developed.

Bioethanol Production by Enzymatic Hydrolysis from Different Lignocellulosic Sources

As the need for non-renewable sources such as fossil fuels has increased during the last few decades, the search for sustainable and renewable alternative sources has gained growing interest. Enzymatic hydrolysis in bioethanol production presents an important step, where sugars that are fermented are obtained in the final fermentation process. In the process of enzymatic hydrolysis, more and more new effective enzymes are being researched to ensure a more cost-effective process. There are many different enzyme strategies implemented in hydrolysis protocols, where different lignocellulosic biomass, such as wood feedstocks, different agricultural wastes, and marine algae are being used as substrates for an efficient bioethanol production. This review investigates the very recent enzymatic hydrolysis pathways in bioethanol production from lignocellulosic biomass.

Preparation and Swelling Behaviors of High-Strength Hemicellulose-g-Polydopamine Composite Hydrogels

Hemicellulose-based composite hydrogels were successfully prepared by adding polydopamine (PDA) microspheres as reinforcing agents. The effects of PDA microsphere size, dosage, and nitrogen content in hydrogel on the mechanical and rheological properties was studied. The compressive strength of hydrogel was increased from 0.11 to 0.30 MPa. The storage modulus G’ was increased from 7.9 to 22.0 KPa. The gaps in the hemicellulose network are filled with PDA microspheres. There is also chemical cross-linking between them. These gaps increased the density of the hydrogel network structure. It also has good water retention and pH sensitivity. The maximum cumulative release rate of methylene blue was 62.82%. The results showed that the release behavior of hydrogel was pH-responsive, which was beneficial to realizing targeted and controlling drug release.

Cellulosic and hemicellulosic fractions of sugarcane bagasse: Potential, challenges and future perspective

Sugarcane bagasse is a rich source of cellulose (32-45%), hemicellulose (20-32%) and lignin (17-32%), 1.0-9.0% ash and some extractives. Huge amount of the generation of sugarcane bagasse has been a great challenge to industries and environment at global level for many years. Though cellulosic and hemicellulosic fractions in bagasse makes it a potential raw substrate for the production of value-added products at large scale, the presence of lignin hampers its saccharification which further leads to low yields of the value-added products. Therefore, an appropriate pretreatment strategy is of utmost importance that effectively solubilizes the lignin that exposes cellulose and hemicellulose for enzymatic action. Pretreatment also reduces the biomass recalcitrance i.e., cellulose crystallinity, structural complexity of cell wall and lignification for its effective utilization in biorefinery. Sugarcane bagasse served as nutrient medium for the cultivation of diverse microorganisms for the production of industrially important metabolites including enzymes, reducing sugars, prebiotic, organic acids and biofuels. Sugarcane bagasse has been utilized in the generation of electricity, syngas and as biosorbant in the bioremediation of heavy metals. Furthermore, the ash generated from bagasse is an excellent source for the synthesis of high strength and light weight bricks and tiles. Present review describes the utility of sugarcane bagasse as sustainable and renewable lignocellulosic substrate for the production of industrially important multifarious value-added products.

Eco-Friendly Bioinspired Interface Design for High-Performance Cellulose Nanofibril/Carbon Nanotube Nanocomposites

Inspired by a wood-like multicomponent structure, an interface-reinforced method was developed to fabricate high-performance cellulose nanofibril (CNF)/carbon nanotube (CNT) nanocomposites. Holocellulose nanofibrils (HCNFs) with core-shell structure were first obtained from bagasse via mild delignification and mechanical defibration process. The well-preserved native hemicellulose as the amphiphilic shell of HCNFs could act as a binding agent, sizing agent, and even dispersing agent between HCNFs and CNTs. Remarkably, both the tensile strength at high relative humidity (83% RH) and electrical conductivity of the HCNF/CNT nanocomposites were significantly improved up to 121 MPa and 321 S/m, respectively, demonstrating great superiority compared to normal CNF/CNT composite films. Furthermore, these HCNF/CNT composites with outstanding integrated performances exhibited great potential in the field of flexible liquid sensing.

Effect of p-TsOH pretreatment on separation of bagasse components and preparation of nanocellulose filaments

The efficient separation of bagasse components was achieved by p-toluenesulfonic acid (p-TsOH) pretreatment. The effects of p-TsOH dosage, reaction temperature and reaction time on cellulose, hemicellulose and lignin contents were studied. Eighty-five per cent of lignin was dissolved, whereas the cellulose loss was minimal (less than 8.1%). Cellulose-rich water-insoluble residual solids were obtained. The degree of polymerization of cellulose decreased slightly, but the crystallinity index (CrI) increased from 52.0% to 68.1%. It indicated that the highly efficient delignification of bagasse was achieved by p-TsOH pretreatment. The nanocellulose filaments (CNFs) were produced by the treated samples. The physico-chemical properties of CNFs were characterized by transmission electron microscopy and thermogravimetric analysis. The results show that the CNFs have smaller average size and higher thermal stability. It provides a new method for CNFs.

Effect of hydrothermal pretreatment on the demineralization and thermal degradation behavior of eucalyptus

Effective removal of alkali and alkaline earth metals (AAEM) is of great significance for promoting biomass pyrolysis. In this study, demineralization via hydrothermal pretreatment was performed, and the effect on the pyrolysis behavior was evaluated by thermogravimetric analysis (TGA) and thermal pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). The effects of reaction temperature, time, and pH on the dissolution rate of K⁺, Ca²⁺, and Mg²⁺ were investigated. The optimal total dissolution rate of the metal elements was 42.10%. Compared with acid leaching, hydrothermal pretreatment allowed a higher crystallinity index. It significantly changed the pyrolysis behavior. The relative content of sugar in pyrolysis products was as high as 58%. The chemical compound distribution was concentrated in the range between C6 and C9, which was conducive for the refinement of gasoline by upgrading. This means that hydrothermal pretreatment has efficient demineralization, which promoted the thermal degradation behavior of biomass.

Effect of Pre-Corrected pH on the Carbohydrate Hydrolysis of Bamboo during Hydrothermal Pretreatment

To confirm the prospects for application of pre-corrected pH hydrothermal pretreatment in biorefineries, the effects of pH on the dissolution and degradation efficiency of carbohydrates were studied. The species composition of the hydrolysate was analyzed using high efficiency anion exchange chromatography and UV spectroscopy. The result showed that the greatest balance between the residual solid and total dissolved solids was obtained at pH 4 and 170 °C. Maximum recovery rates of cellulose and lignin were as expected, whereas hemicellulose had the least recovery rate. The hemicellulose extraction rate was 42.19%, and the oligomer form accounted for 93.39% of the product. The physicochemical properties of bamboo with or without pretreatment was characterized. Compared with the traditional hydrothermal pretreatment, the new pretreatment bamboo has higher fiber crystallinity and thermal stability. In the pretreatment process, the fracture of β-aryl ether bond was inhibited and the structural dissociation of lignin was reduced. The physicochemical properties of bamboo was protected while the hemicellulose was extracted efficiently. It provides theoretical support for the efficient utilization of all components of woody biomass.

Efficient Extraction and Structural Characterization of Hemicellulose from Sugarcane Bagasse Pith

The aim of this study was to investigate the ultrasound-assisted alkaline extraction process and structural properties of hemicellulose from sugarcane bagasse pith. Response surface model (RSM) was established in order to optimize the extraction conditions for the highest hemicellulose yield based on the single-factor experiments. A maximum total hemicellulose yield of 23.05% was obtained under the optimal conditions of ultrasonic treatment time of 28 min, KOH mass concentration of 3.7%, and extraction temperature of 53 °C, and it evidently increased 3.24% compared without ultrasound-assisted extraction. The obtained hemicellulose was analyzed by Fourier transform infrared (FT-IR) spectroscopy. The monosaccharide composition and average molecular weight of hemicellulose were characterized by using ion chromatography (IC) and gel permeation chromatography (GPC). The results indicated that xylose was dominant component in water-soluble hemicellulose (WH, 69.05%) and alkali-soluble hemicellulose (AH, 85.83%), respectively. Furthermore, the monosaccharides (otherwise xylose) and uronic acids contents of WH were higher than that of AH. Weight average molecular weight of WH was 29923 g/mol, lower than that of AH (74,872 g/mol). These results indicate that ultrasonic-assisted alkaline extraction is an efficient approach for the separation of hemicellulose from sugarcane bagasse pith.

Application of engineered yeast strain fermentation for oligogalacturonides production from pectin-rich waste biomass

Citrus wastes disposal is a problem faced by many juice plants due to high disposal costs. However, the citrus peel wastes (CPW) biomass, as bulk bioresources from the agro-industrial waste, is a good source of pectin. Present study aimed to utilize these CPW biomass by engineered yeast strain fermentation with an inexpensive method to produce oligogalacturonides (OGs). The results showed that the engineered yeast strain fermentation can produce significant amounts of OGs with the degree of polymerization ranged from 2 to 7 from the CPW bioresources. Under the optimized conditions using the response surface methodology, the best OGs yield were 26.1%. The present work is the first to use the engineered yeast strain for direct CPW biomass fermentation produced the OGs. We thereby paved a new way to utilize the pectin-rich bioresources.

Lignocellulosic Biomass Mild Alkaline Fractionation and Resulting Extract Purification Processes: Conditions, Yields, and Purities

Fractionation of lignocellulose is a fundamental step in the valorization of cellulose, hemicelluloses, and lignin to produce various sustainable fuels, materials and chemicals. Strong alkaline fractionation is one of the most applied processes since the paper industry has been using it for more than a century, and the mineral acid fractionation process is currently the most applied for the production of cellulosic ethanol. However, in the last decade, mild alkaline fractionation has been becoming increasingly widespread in the frame of cellulosic ethanol biorefineries. It leads to the solubilization of hemicelluloses and lignin at various extent depending on the conditions of the extraction, whereas the cellulose remains insoluble. Some studies showed that the cellulose saccharification and fermentation into ethanol gave higher yields than the mineral acid fractionation process. Besides, contrary to the acid fractionation process, the mild alkaline fractionation process does not hydrolyze the sugar polymers, which can be of interest for different applications. Lignocellulosic mild alkaline extracts contain hemicelluloses, lignin oligomers, phenolic monomers, acetic acid, and inorganic salts. In order to optimize the economic efficiency of the biorefineries using a mild alkaline fractionation process, the purification of the alkaline extract to valorize its different components is of major importance. This review details the conditions used for the mild alkaline fractionation process and the purification techniques that have been carried out on the obtained hydrolysates, with a focus on the yields and purities of the different compounds.

Emerging challenges in the thermal management of cellulose nanofibril-based supercapacitors, lithium-ion batteries and solar cells: A review

In recent years, extensive efforts have been devoted to electronic miniaturization and integration. Accordingly, heating up of electronics has become a critical problem that needs to be urgently solved by efficient and reliable thermal management. Electronic device substrates made of cellulose nanofibrils (CNFs) exhibit outstanding flexibility, mechanical properties, and optical properties. Combining CNFs with high-thermal-conductivly fillers is an effective thermal management technique. This paper focuses on the thermal management of electronic devices and highlights the potential of CNF-based materials for efficient thermal management of energy storage electronic such as supercapacitors, lithium-ion batteries and solar cells. A high-thermal-conductivity composite material for electronic devices can be obtained by combining CNFs as the framework material with carbon nanotubes, graphene, and inorganic nitrides. Moreover, The research progress in the application of CNFs-based materials for supercapacitors, lithium-ion batteries and solar cells is highlighted, and the emerging challenges of different CNFs-based energy storage devices are discussed.

Difference in adsorbable organic halogen formation between phenolic and non-phenolic lignin model compounds in chlorine dioxide bleaching

Adsorbable organic halogen (AOX) is generally formed by the reaction of residual lignin in pulps with chlorine dioxide during bleaching. Lignin has a complex structure. Different functional groups and bonds are present in lignin structures. Phenolic hydroxyl is one of the important functional groups in lignin, and it significantly influences the chemical properties and reactivity. To study the effect of phenolic hydroxyl on AOX formation, vanillyl alcohol (VA) was selected as the phenolic lignin model compound, and veratryl alcohol (VE) was selected as the non-phenolic lignin model compound in this study. The kinetics of AOX formation by the reaction of VA or VE with chlorine dioxide was studied. The effects of pH, chlorine dioxide, lignin model compound concentration and reaction temperature on AOX formation are discussed. The activation energies of the reaction of VA and VE with chlorine dioxide are 16 242.47 J mol^-1 and 281.34 J mol^-1, respectively. Thus, we found that the non-phenolic lignin can react with chlorine dioxide to form AOX more easily than phenolic lignin.

Preparation and Characterization of Nanocomposite Films Containing Nano-Aluminum Nitride and Cellulose Nanofibrils

Nanocomposites consisting of cellulose nanofibrils (CNFs) and nano-aluminum nitride (AlN) were prepared using a simple vacuum-assisted filtration process. Bleached sugarcane bagasse pulp was treated with potassium hydroxide and sodium chlorite, and was subsequently ultra-finely ground and homogenized to obtain CNFs. Film nanocomposites were prepared by mixing CNFs with various AlN amounts (0-20 wt.%). X-ray diffraction revealed that the crystal form of CNF-AlN nanocomposites was different to those of pure CNFs and AlN. The mechanical performance and thermal stability of the CNF-AlN nanocomposites were evaluated through mechanical tests and thermogravimetric analysis, respectively. The results showed that the CNF-AlN nanocomposites exhibited excellent mechanical and thermal stability, and represented a green renewable substrate material. This type of nanocomposite could present great potential for replacing traditional polymer substrates, and could provide creative opportunities for designing and fabricating high-performance portable electronics in the near future.

Fuzzy-Enhanced Modeling of Lignocellulosic Biomass Enzymatic Saccharification

The enzymatic hydrolysis of lignocellulosic biomass incorporates many physico-chemical phenomena, in a heterogeneous and complex media. In order to make the modeling task feasible, many simplifications must be assumed. Hence, different simplified models, such as Michaelis-Menten and Langmuir-based ones, have been used to describe batch processes. However, these simple models have difficulties in predicting fed-batch operations with different feeding policies. To overcome this problem and avoid an increase in the complexity of the model by incorporating other phenomenological terms, a Takagi-Sugeno Fuzzy approach has been proposed, which manages a consortium of different simple models for this process. Pretreated sugar cane bagasse was used as biomass in this case study. The fuzzy rule combines two Michaelis-Menten-based models, each responsible for describing the reaction path for a distinct range of solids concentrations in the reactor. The fuzzy model improved fitting and increased prediction in a validation data set.

Enzymatic pretreatment for cellulose nanofibrils isolation from bagasse pulp: Transition of cellulose crystal structure

In this work, cellulase, low-concentration cold alkali and cellulase combined with cold alkali were used to pretreat unbleached bagasse pulp from which cellulose nanofibrils (CNFs), about 30 nm in diameter, were successfully prepared through ultrafine grinding and high-pressure homogenization. X-ray diffraction analysis showed that cellulase pretreatment increased the crystallinity of CNFs. After low-concentration cold alkali pretreatment, the crystallinity of CNFs significantly reduced and the crystal structure of the cellulose changed from type I to type II. Thermogravimetric analysis showed that CNFs prepared by cellulase combined with cold alkali treatment produced more regenerated cellulose and had lower thermal stability. The use of cellulase and low-concentration cold alkali pretreatments combined with ultrafine grinding and high-pressure homogenization is an environment-friendly method for preparing CNFs. The use of low-concentration cold alkali reduces the consumption of alkali and clean water.

Effect of lignin structure on adsorbable organic halogens formation in chlorine dioxide bleaching

Adsorbable organic halogens (AOX) are formed in pulp bleaching as a result of the reaction of residual lignin with chlorine dioxide. The natural structure of lignin is very complex and it tends to be damaged by various extraction methods. All the factors can affect the study about the mechanism of AOX formation in the reaction of lignin with chlorine dioxide. Lignin model compounds, with certain structures, can be used to study the role of different lignin structures on AOX formation. The effect of lignin structure on AOX formation was determined by reacting phenolic and non-phenolic lignin model compound with a chlorine dioxide solution. Vanillyl alcohol (VA) and veratryl alcohol (VE) were selected for the phenolic and non-phenolic lignin model compound, respectively. The pattern consumption of lignin model compounds suggests that both VA and VE began reacting with chlorine dioxide within 10 min and then gradually steadied. The volume of AOX produced by VE was significantly higher than that produced by VA for a given initial lignin model compound concentration. In a solution containing a combination of VA and VE in chlorine dioxide, VE was the dominant producer of AOX. This result indicates that the non-phenolic lignin structure was more easily chlorinated, while the phenolic lignin structure was mainly oxidized. In addition, AOX content produced in the combined experiments exceeded the total content of the two separate experiments. It suggested that the combination of phenolic and non-phenolic lignin structure can promote AOX formation.

Adsorptive removal of adsorbable organic halogens by activated carbon

Current research mainly focuses on the reduction of adsorbable organic halogen (AOX) sources, while studies on AOX monitoring and management in the environment are scarce. Organic pollutants in water are mainly fixed by sediments. Thus, in this paper, activated carbon was used to simulate the adsorption of AOX by sediments. AOX volatilization and degradation were also studied to exclude their effect on adsorption. Micromolecule chlorides were more easily volatilized and degraded than chlorobenzene and chlorophenol. The adsorption of activated carbon to AOX in bleaching wastewater was also studied and the optimum conditions for AOX removal were elucidated (particle size, 62 µm; time, 120 min; pH, 2.5; temperature, 40°C; and activated carbon dosage, 1.75 g l-1). AOX adsorption by activated carbon is a chemical process. Hence, the chemical compositions of the bleaching effluent with and without adsorption were analysed by GC-MS. The results revealed that activated carbon exhibits a good AOX removal effect, thereby providing a theoretical basis for monitoring the AOX distribution in the environment.

Synthesis and Characterization of Periodate-Oxidized Polysaccharides: Dialdehyde Xylan (DAX)

The cleavage of the C2-C3 bond in the building units of 1 → 4-linked polysaccharides by periodate formally results in two aldehyde units, which are present in several masked forms. The structural elucidation of such polysaccharide dialdehydes remains a big challenge. Since polysaccharide derivatives are increasingly applied in materials technology, unveiling the exact structure is of utmost importance. To address this issue for xylan, dialdehyde xylan (DAX, oxidation degree of 91.5%) has been synthesized as water-soluble polymer. The ATR-FTIR spectrum of DAX showed free aldehyde to be absent and exhibited a characteristic absorption at 858 cm(-1) related to hemiacetal groups. By a combination of 1D and 2D NMR techniques, it was confirmed that oxidized xylan is present as poly(2,6-dihydroxy-3-methoxy-5-methyl-3,5-diyl-1,4-dioxane). Based on GPC analysis, the DAX polymer shows a slightly lower molar mass (6.6 kDa) compared to the starting material (7.7 kDa) right after oxidation, and degraded further after one month of storage in 0.1 M NaCl solution (4.3 kDa). The oxidized xylan demonstrated lower thermal stability upon TGA analysis and a greater amount of residual char (20.6%) compared to the unmodified xylan (13.7%).

Green synthesis of silver nanoparticles with enhanced antibacterial activity using holocellulose as a substrate and reducing agent

The silver nanoparticles with uniform size and well-defined structure have been synthesized by using a hydrothermal method with holocellulose as substrate and reducing agent for silver ions, which exhibited good cytocompatibility and highly toxic.