The demands of energy sustainability drive efforts to bio-chemical conversion of biomass into biofuels through pretreatment, enzymatic hydrolysis, and microbial fermentation. Pretreatment leads to significant structural changes of the complex lignin polymer that affect yield and productivity of the enzymatic conversion of lignocellulosic biomass. Structural changes of lignin after pretreatment include functional groups, inter unit linkages and compositions. These changes influence non-productive adsorption of enzyme on lignin through hydrophobic interaction and electrostatic interaction as well as hydrogen bonding. This paper reviews the relationships between structural changes of lignin and enzymatic hydrolysis of pretreated lignocellulosic biomass. The formation of pseudo-lignin during dilute acid pretreatment is revealed, and their negative effect on enzymatic hydrolysis is discussed.
Cellulose nanocrystals (CNC) have received great research attention since the last few decades due to their extraordinary properties and wide range of applications. In this study, a sustainable and cost-effective method for the synthesis of lignin-containing cellulose nanocrystals (LCNC) from oil palm empty fruit bunch (EFB) is presented. This method is able to retain the lignin in EFB and manifest the properties of lignin. The proposed synthesis process is simpler than the conventional method of producing lignin-coated CNC by first removing the lignin to synthesize CNC followed by the re-coating of lignin on the structure. The samples of LCNC were characterized by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and water contact angle analysis. In addition, by altering the acid concentration during acid hydrolysis process (53% - 60% H2SO4), both surface hydrophobicity (66.0° - 75.1°) and length of LCNC (467 nm-177 nm) can be altered wherein a higher concentration of acid resulted in a greater contact angle and a shorter length of LCNC. Cost and energy analysis deduced that the proposed synthesis method saved about 62% of the total material cost and 80% less energy as compared to the synthesis of lignin-coated CNC.
This study was driven by the stringent environmental legislation concerning the consumption and utilization of eco-friendly materials. Within this context, this paper aimed to examine the characteristics of starch and fibres from the Dioscorea hispida tuber plant to explore their potential as renewable materials. The extraction of the Dioscorea hispida starch and Dioscorea hispida fibres was carried out and the chemical composition, physical, thermal, morphological properties, and crystallinity were studied. The chemical composition investigations revealed that the Dioscorea hispida starch (DHS) has a low moisture t (9.45%) and starch content (37.62%) compared to cassava, corn, sugar palm, and arrowroot starches. Meanwhile, the Dioscorea hispida fibres (DHF) are significantly low in hemicellulose (4.36%), cellulose (5.63%), and lignin (2.79%) compared to cassava, corn hull and sugar palm. In this investigation the chemical, physical, morphological and thermal properties of the Dioscorea hispida fibre and Dioscorea hispida starch were examined by chemical composition investigation, scanning electron microscopy (SEM), particle size distribution, thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), and Fourier transform infrared (FTIR), respectively. It was found that Dioscorea hispida waste is promising alternative biomass and sustainable material with excellent potential as a renewable filler material for food packaging applications.
Over the last decade, the progressive application of natural fibres in polymer composites has had a major effect in alleviating environmental impacts. Recently, there is a growing interest in the development of green materials in a woven form by utilising natural fibres from lignocellulosic materials for many applications such as structural, non-structural composites, household utilities, automobile parts, aerospace components, flooring, and ballistic materials. Woven materials are one of the most promising materials for substituting or hybridising with synthetic polymeric materials in the production of natural fibre polymer composites (NFPCs). These woven materials are flexible, able to be tailored to the specific needs and have better mechanical properties due to their weaving structures. Seeing that the potential advantages of woven materials in the fabrication of NFPC, this paper presents a detailed review of studies related to woven materials. A variety of factors that influence the properties of the resultant woven NFRC such as yarn characteristics, fabric properties as well as manufacturing parameters were discussed. Past and current research efforts on the development of woven NFPCs from various polymer matrices including polypropylene, polylactic acid, epoxy and polyester and the properties of the resultant composites were also compiled. Last but not least, the applications, challenges, and prospects in the field also were highlighted.
The huge amount of agro-wastes generated due to expanding agricultural activities can potentially cause serious environmental and human health problems. Using the biorefinery concept, all parts of agricultural plants can be converted into multiple value-added bioproducts while reducing waste generation. This approach can be viewed as an effective strategy in developing and realizing a circular bioeconomy by accomplishing the dual goals of waste mitigation and energy recovery. However, the sustainability issue of biorefineries should still be thoroughly scrutinized using comprehensive resource accounting methods such as exergy-based approaches. In light of that, this study aims to conduct a detailed exergy analysis of whole-crop safflower biorefinery consisting of six units, i.e., straw handling, biomass pretreatment, bioethanol production, wastewater treatment, oil extraction, and biodiesel production. The analysis is carried out to find the major exergy sink in the developed biorefinery and discover the bottlenecks for further performance improvements. Overall, the wastewater treatment unit exhibits to be the major exergy sink, amounting to over 70% of the total thermodynamic irreversibility of the process. The biomass pretreatment and bioethanol production units account for 12.4 and 10.3% of the total thermodynamic inefficiencies of the process, respectively. The exergy rates associated with bioethanol, biodiesel, lignin, biogas, liquid digestate, seed cake, sodium sulfate, and glycerol are determined to be 5918.5, 16516.8, 10778.9, 1741.4, 6271.5, 15755.8, 3.4, and 823.5 kW, respectively. The overall exergetic efficiency of the system stands at 72.7%, demonstrating the adequacy of the developed biorefinery from the thermodynamic perspective.
The changes in lignocellulosic biomass composition and in vitro rumen digestibility of oil palm empty fruit bunch (OPEFB) after pre-treatment with the fungus Ganoderma lucidum were evaluated. The results demonstrated that the pre-treatment for 2-12 weeks has gradually degraded the OPEFB in a time-dependent manner; whereby lignin, cellulose, and hemicellulose were respectively degraded by 41.0, 20.5, and 26.7% at the end of the incubation period. The findings were corroborated using the physical examination of the OPEFB by scanning electron microscopy. Moreover, the OPEFB pre-treated for 12 weeks has shown the highest in vitro digestibility of dry (77.20%) and organic (69.78%) matter, where they were enhanced by 104.07 and 96.29%, respectively, as compared to the untreated control. The enhancement in the in vitro ruminal digestibility was negatively correlated with the lignin content in the OPEFB. Therefore, biologically delignified OPEFB with G. lucidum fungal culture pre-treatment have the potential to be utilized as one of the ingredients for the development of a novel ruminant forage.
A study was carried out to determine the effectiveness of lignin, extracted from oil palm (Elaeis guineensis) biomass as water-in-oil (W/O) emulsifying agent. To achieve this goal, soda lignin (SL) was extracted via soda pulping process and a series of nanosized soda lignin (NSL) were prepared using homogenizer at three different speed i.e. 10,400 rpm (NSL 10), 11,400 rpm (NSL 11) and 12,400 rpm (NSL 12) for one hour. All prepared samples were characterized by FT-IR, UV-Vis spectroscopy, thermogravimetric analysis (TGA), zeta potential analyser, Transmission Electron Microscope (TEM) and Extreme High Resolution Field Emission Scanning Electron Microscope (XHR-FESEM). The result of FTIR showed that there is no prominent change occurred in spectra of all samples while a good stability was reflected by TGA curves. The percentage of creaming index and visual observations of all samples demonstrated that NSL 12 and dosage 2 g (out of 1 g, 1.5 g and 2 g) were found to be the best among all samples. Furthermore, the results of IFT indicate that NSL 12 was proven to be more stable than the commercial product. Therefore, NSL 12 is selected for toxicological studies and was found safe in both, in vitro and in vivo studies.
Non-healing wounds have placed an enormous stress on both patients and healthcare systems worldwide. Severe complications induced by these wounds can lead to limb amputation or even death and urgently require more effective treatments. Electrospun scaffolds have great potential for improving wound healing treatments by providing controlled drug delivery. Previously, we developed fibrous scaffolds from complex carbohydrate polymers [i.e. chitin-lignin (CL) gels]. However, their application was limited by solubility and undesirable burst drug release. Here, a coaxial electrospinning is applied to encapsulate the CL gels with polycaprolactone (PCL). Presence of a PCL shell layer thus provides longer shelf-life for the CL gels in a wet environment and sustainable drug release. Antibiotics loaded into core-shell fibrous platform effectively inhibit both gram-positive and -negative bacteria without inducting observable cytotoxicity. Therefore, PCL coated CL fibrous gel platforms appear to be good candidates for controlled drug release based wound dressing applications.
Wood-based industry is one of the main drivers of economic growth in Malaysia. Forest being the source of various lignocellulosic materials has many untapped potentials that could be exploited to produce sustainable and biodegradable nanosized material that possesses very interesting features for use in wood-based industry itself or across many different application fields. Wood-based products sector could also utilise various readily available nanomaterials to enhance the performance of existing products or to create new value added products from the forest. This review highlights recent developments in nanotechnology application in the wood-based products industry.
The most critical issues faced by the world nowadays is to provide the sustainability of consumption for energy and natural resources. Lignin is said to be one of the alternative new discoveries best-suited lignocellulosic biomass due to its low cost, sufficient availability and environmentally safe. The valuable properties exhibited by lignin can give broader applications usage such as in composite materials, wood industries, polymer composite industries, pharmaceutical and corrosion inhibitor industries. Many biomass wastes resources, isolation processes and treatments are undergoing development in order to enhance the producing new lignin-based materials on an industrial scale. Therefore, this review discussed on the current knowledge on the structure and chemistry of isolation of lignin from different sources using various common methods, its characterization, properties and its applications.
The feeding trial was conducted to investigate the effect of Azolla spp. inclusion in feed ingredient of broiler chickens. Two hundred of day-old broiler chicks were raised in Farm 15, Faculty of Agriculture, Universiti Putra Malaysia. The birds were individually wing banded, weighed and allocated into four treatment groups (control: 0% of Azolla spp., T1: 5% of Azolla spp., T2: 10% of Azolla spp. and T3: 15% of Azolla spp.). Each group has five replicates and ten birds per pen. All the birds were fed ad libitum during the feeding trial, which lasted 42 days. During the end of the starter and finisher phase, two birds from each replicate were slaughtered. Ileal digesta sample was collected to determine the nutrient digestibility of the Azolla spp. on broiler chickens. Azolla spp. nutritional content was 5.14% dry matter, 24.82% crude protein, 16.64% crude fibre, 2.00% ether extract, 11.59% ash, 34.95% nitrogen-free extract, 42.52% neutral detergent fibre, 31.15% acid detergent fibre, 16.86% acid detergent lignin, 11.37% hemicellulose and 14.29% cellulose. The result from this study showed T3 (15% of Azolla spp.) has significantly highest (p .05) among treatments. For the nutrient digestibility experiment, the findings showed compared with a control group, feeding of 10% or 15% of Azolla spp. led to significant improvement (p
There is an array of methodologies to prepare nanocellulose (NC) and its fibrillated form (CNF) with enhanced physicochemical characteristics. However, acids, bases or organosolv treatments on biomass are far from green, and seriously threaten the environment. Current approach to produce NC/CNF from biomass should be revised and embrace the concept of sustainability and green chemistry. Although hydrothermal process, high-pressure homogenization, ball milling technique, deep eutectic solvent treatment, enzymatic hydrolysis etc., are the current techniques for producing NC, the route designs remain imperfect. Herein, this review highlights the latest methodologies in the pre-processing and isolating of NC/CNF from lignocellulose biomass, by largely focusing on related papers published in the past two years till date. This article also explores the latest advancements in environmentally friendly NC extraction techniques that cooperatively use ball milling and enzymatic hydrolytic routes as an eco-efficient way to produce NC/CNF, alongside the potential applications of the nano-sized celluloses.
In this study, the differences on the physico-chemical parameters, lignocellulose degradation, dynamic succession of microbial community, gene expression of carbohydrate-active enzymes and antibiotics resistance genes were compared during composting systems of bagasse pith/pig manure (BP) and manioc waste/pig manure (MW). The results revealed that biodegradation rates of organic matter, cellulose, hemicellulose and lignin (29.14%, 17.53%,45.36% and 36.48%) in BP were higher than those (15.59%, 16.74%, 41.23% and 29.77%) in MW. In addition, the relative abundance of Bacillus, Luteimonas, Clostridium, Pseudomonas, Streptomyces and expression of genes encoding carbohydrate- active enzymes in BP were higher than those in MW based on metagenomics sequencing. During composting, antibiotics and antibiotic resistance genes were substantially reduced, but the removal efficiency was divergent in the both samples. Taken together, metagenomics analysis was a potential method for evaluating lignocellulose's biodegradation process and determining the elimination of antibiotic and antibiotic resistance genes from different composting sources of biomass.
The valorization of lignin to replace phenol is significant in the production of phenolic resins. However, a great challenge is to produce lignin-based resin (LR) with a suitable viscosity and high substitution rate of lignin to phenol. In this study, LRs were produced using hardwood technical lignin derived from the pulping industry. Structural analysis of the LRs indicated that the unsubstituted para and ortho carbon atoms of the aromatic ring influenced the curing temperature and activation energy of the resins. The curing kinetics and thermal decomposition study implied that urea and methylene groups in cured LRs were significant factors that affected the thermal stability negatively. The prepared LRs showed desirable features if used as adhesives to make plywood. This is the first approach in which a substitution rate of up to 65 % is achieved for low-reactive-site hardwood lignin, which provides a solution to the challenge of the simultaneous realization of the high addition of lignin and the adaptive viscosity of resins.
Fungi of the Trichoderma species are valued industrial enzymes in support of the 'zero-waste' technology to convert agro-industrial biomass into valuable products, i.e. nanocellulose (NC). In this study, an in silico approach using substrate docking and molecular dynamic (MD) simulation was used to predict the order of which the multilayers of cellulosic polymers, i.e. lignin, hemicellulose and cellulose in oil palm leaves (OPL) are degraded by fungal enzymes, endocellulase and exocellulase. The study aimed to establish the catalytic tendencies of the enzymes to optimally degrade the cellulosic components of OPL for high yield production of NC. Energy minimized endocellulase and exocellulase models revealed satisfactory scores of PROCHECK (90.0% and 91.2%), Verify3D (97.23% and 98.85%) and ERRAT (95.24% and 91.00%) assessments. Active site prediction by blind docking, COACH meta-server and multiple sequence alignment indicated the catalytic triads for endocellulase and exocellulase were Ser116-His205-Glu249 and Ser382-Arg124-Asp385, respectively. Binding energy of endocellulase docked with hemicellulose (-6.0 kcal mol-1) was the most favourable followed by lignin (-5.6 kcal mol-1) and cellulose (-4.4 kcal mol-1). Exocellulase, contrarily, bonded favorably with lignin (-8.7 kcal mol-1), closely followed by cellulose (-8.5 kcal mol-1) and hemicellulose (-8.4 kcal mol-1). MDs simulations showed that interactions of complexes, endocellulase-hemicellulose and the exocellulase-cellulose being the most stable. Thus, the findings of the study successfully identified the specific actions of sugar-acting enzymes for NC production. Communicated by Ramaswamy H. Sarma.
Mechanical strength, thermal conductivity and electrical breakdown of polypropylene/lignin/kenaf core fiber (PP/L/KCF) composite were studied. PP/L, PP/KCF and PP/L/KCF composites with different fiber and lignin loading was prepared using a compounding process. Pure PP was served as control. The results revealed that tensile and flexural properties of the PP/L/KCF was retained after addition of lignin and kenaf core fibers. Thermal stability of the PP composites improved compared to pure PP polymer. As for thermal conductivity, no significant difference was observed between PP composites and pure PP. However, PP/L/KCF composite has higher thermal diffusivity. All the PP composites produced are good insulating materials that are suitable for building. All PP composites passed withstand voltage test in air and oil state as stipulated in IEC 60641-3 except PP/L in oil state. SEM micrograph showed that better interaction and adhesion between polymer matrix, lignin and kenaf core fibers was observed and reflected on the better tensile strength recorded in PP/L/KCF composite. This study has successfully filled the gap of knowledge on using lignin and kenaf fibers as PP insulator composite materials. Therefore, it can be concluded that PP/Lignin/KCF has high potential as an insulating material.
Lignin depolymerization for the purpose of synthesizing aromatic molecules is a growing focus of research to find alternative energy sources. In current studies, the photocatalytic depolymerization of lignin has been investigated by two new iso-propylamine-based lead chloride perovskite nanomaterials (SK9 and SK10), synthesized by the facile hydrothermal method. Characterization was done by Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), UV-Visible (UV-Vis), Photoluminescence (PL), and Fourier-Transform Infrared (FTIR) Spectroscopy and was used for the photocatalytic depolymerization of lignin under UV light. Lignin depolymerization was monitored by taking absorption spectra and catalytic paths studied by applying kinetic models. The %depolymerization was calculated for factors such as catalyst dose variation, initial concentration of lignin, and varying temperatures. Pseudo-second order was the best suited kinetic model, exhibiting a mechanism for lignin depolymerization that was chemically rate controlled. The activation energy (Ea) for the depolymerization reaction was found to be 15 kJ/mol, which is remarkably less than conventional depolymerization of the lignin, i.e., 59.75 kJ/mol, exhibiting significant catalytic efficiencies of synthesized perovskites. Products of lignin depolymerization obtained after photocatalytic activity at room temperature (20 °C) and at 90 °C were characterized by GC-MS analysis, indicating an increase in catalytic lignin depolymerization structural subunits into small monomeric functionalities at higher temperatures. Specifically, 2-methoxy-4-methylphenol (39%), benzene (17%), phenol (10%) and catechol (7%) were detected by GC-MS analysis of lignin depolymerization products.
Heavy metal pollution, such as lead, can cause contamination of water resources and harm human life. Many techniques have been explored and utilized to overcome this problem, with adsorption technology being the most common strategies for water treatment. In this study, carbon nanofibers, polyacrylonitrile (PAN)/sago lignin (SL) carbon nanofibers (PAN/SL CNF) and PAN/SL activated carbon nanofibers (PAN/SL ACNF), with a diameter approximately 300 nm, were produced by electrospinning blends of polyacrylonitrile and sago lignin followed by thermal and acid treatments and used as adsorbents for the removal of Pb(II) ions from aqueous solutions. The incorporation of biodegradable and renewable SL in PAN/SL blends fibers produces the CNF with a smaller diameter than PAN only but preserves the structure of CNF. The adsorption of Pb(II) ions on PAN/SL ACNF was three times higher than that of PAN/SL CNF. The enhanced removal was due to the nitric acid treatment that resulted in the formation of surface oxygenated functional groups that promoted the Pb(II) ions adsorption. The best-suited adsorption conditions that gave the highest percentage removal of 67%, with an adsorption capacity of 524 mg/g, were 40 mg of adsorbent dosage, 125 ppm of Pb(II) solution, pH 5, and a contact time of 240 min. The adsorption data fitted the Langmuir isotherm and the pseudo-second-order kinetic models, indicating that the adsorption is a monolayer, and is governed by the availability of the adsorption sites. With the adsorption capacity of 588 mg/g, determined via the Langmuir isotherm model, the study demonstrated the potential of PAN/SL ACNFs as the adsorbent for the removal of Pb(II) ions from aqueous solution.
Lignin from kenaf (Hibiscus cannabinus) core was investigated as an alternative filler for rubber. Three types of extraction methods were used to isolate lignin from kenaf, namely kraft, soda and organosolv process. The particle size, surface area, functionalities changes, molecular weight and thermal properties of the lignin were characterized. The results showed that Kraft lignin (KL) has the smallest particle size (40.41 μm) compared to soda lignin (SL) (63.85 μm) and organosolv lignin (OL) (66.85 μm). This is in good agreement with the BET surface area of 9.52 m2/g, 1.25 m2/g and 2.40 m2/g respectively. However, the smaller surface area of SL compared to OL is due to the smaller pore size and pore volume of SL. KL also showed high hydroxyl content with corresponding high thermal stability as confirmed by NMR and TGA. The thermal stability of the lignin correlates well with the molecular weight (MW). From the overall characteristics, it can be concluded that KL, SL and OL can be used as an alternative filler in rubber compounds to substitute common fillers like silica and carbon.
This study investigated the interactions between volatile and char during biomass pyrolysis at 400 °C, employing a β-5 lignin dimer and amino-modified graphitized carbon nanotube (CNT-NH2) as their models, respectively. The results demonstrated that both -NH2 and its carrier (CNT) facilitated the conversion of the β-5 dimer, which significantly increased from 9.7% (blank run), to 61.6% (with CNT), and to 96.6% (with CNT-NH2). CNT mainly favored the breakage of C-O bond in the feedstock to produce dimers with a yield of 55.5%, while CNT-NH2 promoted the cleavage of both C-O and C-C bonds to yield monomers with a yield up to 63.4%. Such significant changes in the pyrolysis behaviors of the β-5 lignin dimer after the introduction of CNT-NH2 were considered to be mainly caused by hydrogen-bond formations between -NH2 and the dimeric feedstock/products, in addition to the π-π stacking between CNT and aromatic rings.