Green route to modification of wood waste, cellulose and hemicellulose using reactive extrusion

Valorization of Grain and Oil By-Products with Special Focus on Hemicellulose Modification

Hemicellulose is one of the most important natural polysaccharides in nature. Hemicellulose from different sources varies in chemical composition and structure, which in turn affects the modification effects and industrial applications. Grain and oil by-products (GOBPs) are important raw materials for hemicellulose. This article reviews the modification methods of hemicellulose in GOBPs. The effects of chemical and physical modification methods on the properties of GOBP hemicellulose biomaterials are evaluated. The potential applications of modified GOBP hemicellulose are discussed, including its use in film production, hydrogel formation, three-dimensional (3D) printing materials, and adsorbents for environmental remediation. The limitations and future recommendations are also proposed to provide theoretical foundations and technical support for the efficient utilization of these by-products.

Incorporation of canola meal as a sustainable natural filler in PLA foams

The canola oil industry generates significant waste as canola meal (CM) which has limited scope and applications. This study demonstrates the possibility of valorization of CM as a sustainable natural filler in a biodegradable polymer composite of Poly(lactic acid) (PLA). Generally, interfacial bonding between natural fibers and the polymer matrix in the composite is weak and non-uniform. One possible solution is to derivatize natural fibre to introduce interfacial bond strength and compatibility with the PLA polymer matrix. Here, CM was succinylated in a reactive extrusion process using succinic anhydride at 30 wt% to get 14% derivatization with 0.02 g of -COOH density per g of CM. The CM or succinylated CM at 5 and 15 wt% was co-extruded with amorphous PLA to get composite fibers. CM-PLA and succinylated CM-PLA biocomposites were foamed using a mild and green microcellular foaming process, with CO2 as an impregnating agent without any addition of organic solvents. The properties of the foams were analyzed using differential scanning calorimetry (DSC), Dynamic mechanical thermal analysis (DMTA), shrinkage, and imaging. The addition of CM or succinylated CM as a natural filler did not significantly change the glass transition temperature, melting point, percent crystallization, stiffness, and thermal stability of PLA foams. This suggests succinylation (modification) of CM is not a mandatory step for improving interphase compatibility with the amorphous PLA. The new PLA-CM foams can be a good alternative in the packaging industry replacing the existing petroleum-based polymer foams.

Synthesis and its biological activity of carboxymethyl hemicellulose p-hydroxybenzoate (P-CMHC)

Hemicellulose extracted from ecalyptus APMP pulping waste liquor and undergoes etherification modification to produce carboxymethyl hemicellulose (CMHC). Subsequently, CMHC undergoes esterification reaction with p-hydroxybenzoic acid to synthesize a novel polysaccharide-based preservative known as carboxymethyl hemicellulose p-hydroxybenzoate (P-CMHC). The synthesis conditions of P-CMHC were optimized using the response surface methodology, resulting in an optimal esterification condition that achieved a degree of substitution of 0.232. P-CMHC exhibits excellent antioxidant activity, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging activities. Additionally, it demonstrates favorable hygroscopic and moisturizing properties. Thiazole blue (MTT) experiments evaluating cell proliferation rate indicate that P-CMHC possesses negligible cytotoxicity, making it a promising, safe, and healthy preservative. Consequently, it can be considered as a new material for applications in the fields of biomedicine, food, and cosmetics.

Compatibility of Sustainable Mater-Bi/poly(ε-caprolactone)/cellulose Biocomposites as a Function of Filler Modification

Despite their popularity and multiplicity of applications, wood-polymer composites (WPCs) still have to overcome particular issues related to their processing and properties. The main aspect is the compatibility with plant-based materials which affects the overall performance of the material. It can be enhanced by strengthening the interfacial adhesion resulting from physical and/or chemical interactions between the matrix and filler, which requires introducing a compatibilizer or a proper modification of one or both phases. Herein, the impact of cellulose filler modifications with varying contents (1-10 wt%) of hexamethylene diisocyanate (HDI) on the compatibility of Mater-Bi/poly(ε-caprolactone) (PCL)-based biocomposites was evaluated. An analysis of surface wettability revealed that the filler modification reduced the hydrophilicity gap between phases, suggesting compatibility enhancement. It was later confirmed via microscopic observation (scanning electron microscopy (SEM) and atomic force microscopy (AFM)), which pointed to the finer dispersion of modified particles and enhanced quality of the interface. The rheological analysis confirmed increased system homogeneity by the reduction in complex viscosity. In contrast, thermogravimetric analysis (TGA) indicated the efficient modification of filler and the presence of the chemical interactions at the interface by the shift of thermal decomposition onset and the changes in the degradation course.

Technological limitations in obtaining and using cellulose biocomposites

Among the many possible types of polymer composite materials, the most important are nanocomposites and biocomposites, which have received tremendous attention in recent years due to their unique properties. The fundamental benefits of using biocomposites as alternative materials to “petroleum-based” products are certainly shaping current development trends and setting directions for future research and applications of polymer composites. A dynamic growth of the production and sale of biocomposites is observed in the global market, which results not only from the growing interest and demand for this type of materials, but also due to the fact that for the developed and modified, thus improved materials, the area of their application is constantly expanding. Already today, polymer composites with plant raw materials are used in various sectors of the economy. In particular, this concerns the automotive and construction industries, as well as widely understood packaging. Bacterial cellulose, for example, also known as bionanocellulose, as a natural polymer with specific and unique properties, has been used extensively,primarily in numerous medical applications. Intensive research is also being carried out into composites with natural fibres composed mainly of organic compounds such as cellulose, hemicellulose and lignin. However, three aspects seem to be associated with the popularisation of biopolymers: performance, processing and cost. This article provides a brief overview of the topic under discussion. What can be the technological limitations considering the methods of obtaining polymer composites with the use of plant filler and the influence on their properties? What properties of cellulose constitute an important issue from the point of view of its applicability in polymers, in the context of compatibility with the polymer matrix and processability? What can be the ways of changing these properties through modifications, which may be crucial from the point of view of the development directions of biopolymers and bioplastics, whose further new applications will be related, among others, to the enhancement of properties? There still seems to be considerable potential to improve the cellulose material composites being produced, as well as to improve the efficiency of their manufacturing. Nevertheless, the material still needs to be well optimized before it can replace conventional materials at the industrial level in the near future. Typically, various studies discuss their comparison in terms of production, properties and highly demanding applications of plant or bacterial nanocellulose. Usually, aspects of each are described separately in the literature. In the present review, several important data are gathered in one place, providing a basis for comparing the types of cellulose described. On the one hand, this comparison aims to demonstrate the advantage of bacterial cellulose over plant cellulose, due to environmental protection and its unique properties. On the other hand, it aims to prepare a more comprehensive point of view that can objectively help in deciding which cellulosic raw material may be more suitable for a particular purpose, bacterial cellulose or plant cellulose.

An Overview of Extrusion as a Pretreatment Method of Lignocellulosic Biomass

Lignocellulosic biomass is both low cost and abundant, and unlike energy crops, can escape associated ethical dilemmas such as arable land use and food security issues. However, their usage as raw material in a biorefinery implies an inherent upstream pretreatment step to access compounds of interest derived from lignocellulosic biomass. Importantly, the efficiency of this step is determinant for the downstream processes, and while many pretreatment methods have been explored, extrusion is both a very flexible and promising technology. Extrusion is well-known in both the polymer and pharmaceutical industries and has been used since the 18th century. However, as a pretreatment method for lignocellulosic biomass, extrusion is relatively new. The first use for this purpose dates back to the 1990s. Extrusion enjoys a high degree of flexibility due to the many available parameters, but an understanding of extrusion requires a knowledge of these parameters and the different relationships between them. In this paper, we present a concise overview of lignocellulosic biomass extrusion by reviewing key extrusion parameters and their associated extruder design components and operating conditions.

Mechanochemical Transformations of Biomass into Functional Materials

Biomass is one of the promising alternatives to petroleum-derived materials and plays a major role in our fight against climate change by providing renewable sources of chemicals and materials. Owing to its chemical and structural complexity, the transformation of biomass into value-added products requires a profound understanding of its composition at different scales and innovative methods such as combining physical and chemical processes. In this context, the use of mechanochemistry in biomass valorization is currently growing owing to its potentials as an efficient, sustainable, and environmentally friendly approach. This review highlights the latest advances in the transformation of biomass (i. e., chitin, cellulose, hemicellulose, lignin, and starch) to functional materials using mechanochemical-assisted methods. We focused here on the methodology of biomass processing, influencing factors, and resulting properties with an emphasis on achieving functional materials rather than breaking down the biopolymer chains into smaller molecules. Opportunities and limitations associated this methodology were discussed accordingly for future directions.

Mesoporous aluminum impregnated rubber seed shell waste enriched with calcium as adsorbent material for the removal of microbial DNA in aqueous solution

Water contamination by pathogens and diseases induced by these pathogens is a major water quality issue all over the world. Poor public health has been linked to tap water polluted with DNA harboring antibiotic resistance genes sequence. According to HSAB concept, surface modification of rubber seed shell waste with alumina (AIRSS) as novel agro-waste adsorbent creates more active surface constituents for DNA adsorption. The proximate, ultimate and EDAX analysis provides the percentage levels of ash concentration, volatile, moisture and fixed carbon content, elemental composition present in the adsorbent. The structural features of AIRSS were determined using FT-IR, SEM and XRD. In order to improve reaction conditions, the effect of pH, temperature, adsorbent amount, and reaction time is also examined. The highest percent of DNA removal (92.5%) was achieved at the optimum conditions: 2 g/L at pH 4, contact time 120 minutes as compared to the conventional methods. The DNA adsorbs onto the surface of AIRSS through physical (vander Waals force) and chemical interactions, as demonstrated by kinetics and spectroscopic analyses. Changes in enthalpy (H), free energy (G), and entropy (S) indicate that adsorption is a spontaneous and exothermic process, according to thermodynamic parameters. The results of the experiments showed that the prepared AIRSP adsorbent could be used to remove DNA from water. The efficacy of AIRSS for the removal of DNA has decreased after nine months of storage and use. Low pH and the presence of AIRSS improved DNA-AIRSS adsorption, according to our findings.

High-Solids, Solvent-Free Modification of Engineered Polysaccharides

The nature-identical engineered polysaccharide α-(1,3) glucan, produced by the enzymatic polymerization of sucrose, was chemically modified by acylation with succinic anhydride. This modification reaction was initially performed at the micro scale in a TGA reactor to access a range of reaction conditions and to study the mechanism of the reaction. Subsequently, the best performing conditions were reproduced at the larger laboratory scale. The reaction products were characterized via coupled TGA/DSC analysis, FT-IR spectroscopy, solution viscosity and pH determination. The acylation path resulted in partially modifying the polysaccharide by altering its behavior in terms of thermal properties and solubility. The acylation in a solvent-free approach was found promising for the development of novel, potentially melt-processable and fully bio-based and biodegradable ester compounds.

Solvent-free production of thermoplastic lignocellulose from wood pulp by reactive extrusion

A novel acylation approach suited to rapid bulk thermoplasticization of lignocellulose without solvents was previously demonstrated by the authors in benchtop batch studies. The method relies upon a benzethonium chloride/sulfuric acid functionalizing agent at low concentrations to act as a wetting agent for the wood pulp, similar to an ionic liquid, yet binds to the lignocellulose ester as a flow aid in the final thermoplastic. The present investigation evaluates the approach in a residence time-limited (45-90 s) continuous twin-screw reactor, where intensive mixing and heat were found to yield high acylation. The modified lignocellulose exhibited desired thermoplasticity by being melt moldable without the need for plasticizers and maintained much of the excellent stiffness of cellulose, demonstrating a maximum flexural modulus of 5.4 GPa and tensile modulus of 1.8 GPa. The influence of extrusion conditions on thermoplasticity was examined by a Design of Experiments (DOE) analysis.

Surface Modification of Cellulose from Oat Hull with Citric Acid Using Ultrasonication and Reactive Extrusion Assisted Processes

This study aimed to produce modified cellulose extracted from oat hulls by an esterification reaction with citric acid (CA) employing ultrasonication and reactive extrusion assisted processes. Modified samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (DRX), scanning electron microscopy (SEM), wettability, oil and water absorption capacities, water adsorption capacity, and thermal stability. From FTIR results it can be observed a new band for all modified samples at 1735 cm−1, confirming the esterification. The morphology and crystallinity pattern of fibers were not affected by esterification, and crystallinity indexes ranged from 43% (unmodified cellulose) to 44–49% in modified samples. Both groups of samples, obtained by ultrasonication and reactive extrusion, showed decreases in water absorption capacities (1.63–1.71 g/g) compared to unmodified cellulose (9.38 g/g). It was observed an increase in oil retention capacity from 1.80 g/g (unmodified cellulose) to 4.57–7.31 g/g after esterification, and also the modified samples presented higher affinity by a non-polar solvent in the wettability test. The new properties of modified cellulose expand its use in the industry and prove that ultrasonication and reactive extrusion can be used to obtain esterified cellulose, being eco-friendly, simple, and convenient processes with short reaction times.

Multiscale modelling investigation of wood modification with acetic anhydride

Density functional theory (DFT) and molecular dynamics (MD) simulations were employed to investigate the interaction of cellulose and lignin with acetic anhydride for explaining the wood modification process. Cellulose was modelled with a cellobiose unit and dibenzodioxocin was used to represent the lignin model. Results obtained from both methods revealed that acetic anhydride interacted substantially more with the cellobiose model than the lignin model. The interaction energy of cellobiose-acetic anhydride was higher (about 20 kJ mol-1) than that of lignin-acetic anhydride. DFT results on hydrogen bonding indicated that the hydroxyl group from cellobiose and the aromatic hydroxyl group from lignin models have similar energy values, which explain the equal strength of hydrogen bond interaction. The same trend was also obtained for the substitution of acetyl group in the hydroxyl group. MD results have also predicted that acetic anhydride forms a stronger interaction with cellobiose than with the lignin model, and these findings were in agreement with the DFT results.

An overview of biomass conversion: exploring new opportunities

Recycling biomass is indispensable these days not only because fossil energy sources are gradually depleted, but also because pollution of the environment, caused by the increasing use of energy, must be reduced. This article intends to overview the results of plant biomass processing methods that are currently in use. Our aim was also to review published methods that are not currently in use. It is intended to explore the possibilities of new methods and enzymes to be used in biomass recycling. The results of this overview are perplexing in almost every area. Advances have been made in the pre-treatment of biomass and in the diversity and applications of the enzymes utilized. Based on molecular modeling, very little progress has been made in the modification of existing enzymes for altered function and adaptation for the environmental conditions during the processing of biomass. There are hardly any publications in which molecular modeling techniques are used to improve enzyme function and to adapt enzymes to various environmental conditions. Our view is that using modern computational, biochemical, and biotechnological methods would enable the purposeful design of enzymes that are more efficient and suitable for biomass processing.

Effective treatment and utilization of hazardous waste sulfuric acid generated from alkylation by lignocellulose ester-catalyzed oxidative degradation of organic pollutants

Alkylation reaction catalyzed by concentrated H₂SO₄ generates hazardous waste H₂SO₄ containing a large amount of organic pollutants. This study focused on effective utilization and treatment of the waste H₂SO₄ for simultaneous consumption of H₂SO₄ and deep oxidative degradation of the organics. The waste H₂SO₄ could completely react with magnesium oxide ore to prepare crude MgSO₄ solution, and the organic pollutants in the solution were deeply degraded and mainly mineralized to H₂O and CO₂ with H₂O₂ as oxidant and sugarcane bagasse citrate (SBC), a kind of lignocellulose ester, as catalyst. The total amount of acidic groups of SBC significantly affected its catalytic activity, attributing to that these oxygen-containing functional groups adsorbed and immobilized metal ions on SBC to form catalytic active sites, which could activate and catalyze H₂O₂ to generate •OH and HO₂• radicals for effective degradation of the organics. The resulting purified MgSO₄ solution with color removal of 93.71% and total organic carbon removal of 85.89% under optimum catalytic reaction conditions was used to produce qualified MgSO₄∙7H₂O product. These results highlighted the feasibility of using lignocellulose ester as effective catalyst for deep oxidative degradation of hazardous organic pollutants.

Mechanochemical esterification of waste mulberry wood by wet Ball-milling with tetrabutylammonium fluoride

Esterification of lignocellulosic biomass driven by dry ball-milling suffered from agglomeration of lignocellulosic matters during milling process. In this study, esterification of waste mulberry wood (MW) was carried out by wet ball-milling with water and tetrabutylammonium fluoride (TBAF) to prepare all-wood-plastic composites. Under the same condition, the esterification of MW by wet ball-milling with TBAF presented higher efficiency than that without TBAF which was attributed to catalytic function of F^- ions meanwhile the binding of TBA⁺ to cellulose fibrils hindered the compaction of fibrillated fragments. Pre-ball-milling of MW for 4.0 h apparently promoted the esterification with succinic anhydride. All-wood-plastic composites prepared after 7.0 h succinoylation demonstrated prominent mechanical performance due to strong adhesion of fragments and matrix. This study is supposed to provide an environment-friendly method for efficient conversion of waste lignocellulosic biomass.

Development of an advanced integrative process to create valuable biosugars including manno-oligosaccharides and mannose from spent coffee grounds

Spent coffee grounds (SCG) or coffee residue wastes (CRW) provide excellent raw material for mannose and bioethanol production. In this study, SCG were used to produce valuable biosugars, including oligosaccharides (OSs), manno-oligosaccharides (MOSs), mannose, and bioethanol. SCG were subjected to delignification and defatting, producing SCG-derived polysaccharides. Two-stage enzymatic hydrolysis (short- and long-term) was performed to produce short-chain manno-oligosaccharides (MOSs) and monosaccharides (MSs), respectively. From 100 g dry weight (DW) amounts of SCG, approximately 77 g delignified SCG and 61 g SCG-derived polysaccharides, amounts of 15.9 g of first biosugars (mostly MOSs), 25.6 g of second biosugars (mostly MSs), and 3.1 g of bioethanol, were recovered. This technique may aid in the production of high-value mannose and OSs from SCG and other lignocellulosic biomasses that contain specific polysaccharides.

Development of an integrated process to produce d-mannose and bioethanol from coffee residue waste

A novel, integrated process for economical high-yield production of d-mannose and ethanol from coffee residue waste (CRW), which is abundant and widely available, was reported. The process involves pretreatment, enzymatic hydrolysis, fermentation, color removal, and pervaporation, which can be performed using environmentally friendly technologies. The CRW was pretreated with ethanol at high temperature and then hydrolyzed with enzymes produced in-house to yield sugars. Key points of the process are: manipulations of the fermentation step that allowing bioethanol-producing yeasts to use almost glucose and galactose to produce ethanol, while retaining large amounts of d-mannose in the fermented broth; removal of colored compounds and other components from the fermented broth; and separation of ethanol and d-mannose through pervaporation. Under optimized conditions, approximately 15.7g dry weight (DW) of d-mannose (approximately 46% of the mannose) and approximately 11.3g DW of ethanol from 150g DW of ethanol-pretreated CRW, were recovered.

Modification of proteins and polysaccharides using dodecenyl succinic anhydride: Synthesis, properties and applications-A review

Proteins and polysaccharides are among the biopolymers produced by living organisms for their structural integrity, protection, physiological functions, or as reserve energy. These biopolymers are extracted from their natural matrices by humans to fulfil basic as well as convenience needs. The inquisitive human nature, ever-growing demands and resources at disposal have led to copious research in the field of biopolymer modifications. The availability of reactive sites on these biopolymers make them suitable substrates for esterification, etherification, oxidation, epoxidation, N-acylation, alkylation, etc. Dodecenyl succinic anhydride (DDSA) is an esterifying agent that introduces a 12-carbon hydrophobic chain in the structure of the substrate containing suitable reactive sites. The use of DDSA as a modifying agent for biopolymers dates back to the mid-twentieth century. Even today, many biopolymers are explored for modification with DDSA for improved functionality. These modifications are aimed at catering the needs of the paint, pharmaceutical, cosmetic, food and textile industries. This review attempts to systematically compile reported research on the use of DDSA as a biopolymer modifying agent, the various reaction techniques, properties and applications thereof.

Fabrication, characterization, and application of polyester/wood flour composites

The mechanical properties, thermal properties, antibacterial activity, and fabrication of three-dimensional (3D) printing strips of composite materials containing polyhydroxyalkanoate (PHA) and wood flour (WF) were evaluated. Maleic anhydride (MA)-grafted PHA (PHA-g-MA) and WF were used to enhance the desired characteristics of these composites. The PHA-g-MA/WF composites had better mechanical properties than the PHA/WF composites did. This effect was attributed to a greater compatibility between the grafted polyester and WF. Additionally, the PHA-g-MA/WF composites provided higher quality 3D printing strips and were more easily processed because of ester formation. The water resistance of the PHA-g-MA/WF composite was greater than that of PHA/WF. Moreover, WF enhanced the antibacterial activity of the composites. Composites of PHA-g-MA or PHA containing WF had better antibacterial activity.

Modification of Cellulose with Succinic Anhydride in TBAA/DMSO Mixed Solvent under Catalyst-Free Conditions

Homogeneous modification of cellulose with succinic anhydride was performed using tetrabutylammonium acetate (TBAA)/dimethyl sulfoxide (DMSO) mixed solvent. The molar ratio of succinic anhydride (SA) to free hydroxyl groups in the anhydroglucose units (AGU), TBAA dosage, reaction temperature, and reaction time were investigated. The highest degree of substitution (DS) value of 1.191 was obtained in a 10 wt% TBAA/DMSO mixed solvent at 60 °C for 60 min, and the molar ratio of SA/AGU was 6/1. The molar ratio of SA/AGU and the TBAA dosage showed a significant influence on the reaction. The succinoylated cellulose was characterized by ATR-FTIR, TGA, XRD, solid state CP/MAS ¹³C NMR spectroscopy (CP/MAS ¹³C NMR), and SEM. Moreover, the modified cellulose was applied for the adsorption of Cu²⁺ and Cd²⁺, and both the DS values of modified cellulose and pH of the heavy metal ion solutions affected the adsorption capacity of succinylated cellulose. The highest capacity for Cu²⁺ and Cd²⁺ adsorption was 42.05 mg/g and 49.0 mg/g, respectively.

Novel superabsorbent membranes made of PVA and Ziziphus spina-christi cellulose for agricultural and horticultural applications

Novel superabsorbent membranes consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs) from Ziziphus spina-christi fibers (ZSP-fibers), glutaraldehyde (GLA) and glycerin (G) were prepared using a Hydraulic Lamination Hot Press machine.

Integrated analysis of solid-state NMR spectra and nuclear magnetic relaxation times for the phenol formaldehyde (PF) resin impregnation process into soft wood

Integrated analysis using a solid-state NMR method revealed that PF resin permeated not only lignin but also carbohydrate polymers.

Micromorphological changes and mechanism associated with wet ball milling of Pinus radiata substrate and consequences for saccharification at low enzyme loading

In this work, substrates prepared from thermo-mechanical treatment of Pinus radiata chips were vibratory ball milled for different times. In subsequent enzymatic hydrolysis, percent glucan conversion passed through a maximum value at a milling time of around 120min and then declined. Scanning electron microscopy revealed breakage of fibers to porous fragments in which lamellae and fibrils were exposed during ball milling. Over-milling caused compression of the porous fragments to compact globular particles with a granular texture, decreasing accessibility to enzymes. Carbon-13 NMR spectroscopy showed partial loss of interior cellulose in crystallites, leveling off once fiber breakage was complete. A mathematical model based on observed micromorphological changes supports ball milling mechanism. At a low enzyme loading of 2FPU/g of substrate and milling time of 120min gave a total monomeric sugar yield of 306g/kg of pulp which is higher than conventional pretreatment method such as steam exploded wood.