High Hemicellulose Research Articles

CELL-WALL COMPOSITION AND DIGESTIBILITY OF FIVE NATIVE SHRUBS OF THE TAMAULIPAN THORNSCRUB IN NORTHEASTERN MEXICO

<p><strong>Background: </strong>Many trees and shrubs from different parts of the world have forage potential, because they are inexpensive local products used for small ruminants as feed resource, some of these native shrubs are currently already an important fodder resources in arid and semi-arid regions of Northeastern México. <strong>Objective:</strong> The aim of this study was to determine the cell-wall composition and <em>in vitro</em> leaf digestibility of five shrub species: <em>Celtis pallida</em>, <em>Croton suaveolens</em>, <em>Forestiera angustifolia</em>, <em>Guaiacum angustifolium</em> and <em>Parkinsonia aculeata</em>. <strong>Methodology: </strong>Plant material was collected monthly from July 2018 to June 2019 at two sampling sites in Nuevo León, México: Linares and Los Ramones Counties. <em>In vitro</em> dry matter digestibility (IVDMD) was calculated using the Daisy<sup>II</sup> incubator. <strong>Results: </strong>Non-structural carbohydrates (NSC) (total mean = 22.4% dry matter) varied significantly among species, sites, and months (p<0.001, p<0.05 and p<0.001, respectively). Conversely, neither acid detergent lignin (ADL) (8.4%), crude protein (CP) (21.9%), cellulose (12.5%), hemicellulose (20.8%), nor IVDMD (75.5%) varied significantly between sites. In general, NSC values were higher in Linares. The highest and lowest IVDMD values as per the Daisy<sup>II</sup> incubator were recorded in March and September, respectively. <em>C</em>. <em>pallida</em> showed the highest IVDMD associated with a high hemicellulose and low ADL values, whereas <em>P</em>. <em>aculeata</em> showed a lower IVDMD value and high cellulose content. <strong>Implications: </strong>All species maintained considerably high levels of digestibility, which might indicate an availability of high CP levels for consumption by ruminants in the semi-arid regions of northeastern México. <strong>Conclusion:</strong> It is concluded that the species under study can be considered as emergency feed resources for small ruminants throughout the year.</p>

Mechanization of fibre extraction: an eco-friendly alternative method of jute retting

Jute retting has become a major obstacle for cultivation of jute due to water scarcity. Not only that, the water retting generates waste water and causes environmental pollution. This experiment was conducted to extract fibre through a mechanical process instead of extracting traditional water retting to overcome the problem. Machine extraction and water retting methods were applied to non-retted ribbons. Physico- chemical properties were then determined of the extracted fibre samples. The promising result obtained that the fibre extraction from ribbon is possible by the developed fibre extractor machine. Machine extracted fibre of the bottom portion shows similar strength and luster property like water retted fibre of the bottom. Middle portion of the machine extracted fibre showed a significantly higher luster property compared to water retted middle portion. Machine extracted fibres were coarse compared to water retted fibre. Water retting process produced finer quality fibre. Machine extracted fibres contain lower cellulose, higher hemicellulose and higher lignin compared to water retted fibre. These results show the possibility of developing alternative bast fibre extraction processes employing machine not undergoing water retting method.

Physiochemical Characterization and Potential of Synthesis Gas Production from Rubber Wood Biomass by Using Downdraft Gasifier

Bioenergy has gained great interest in the recent years for being environmentally friendly and renewable energy resource. Southern Thailand is well-known for agro-industry including rubber tree plantations and processing, which provide biomass that could be applied to produce bioenergy. Thus, this study aimed to investigate the energy potential of Rubber Wood Chips (RWC), Rubber Wood Pellets (RWP), Unburned Char (UBC) from rubber wood, blended RWC:UBC (50:50%) and blended RWP:UBC (50:50%). The physiochemical properties including bulk density, proximate composition, ultimate composition, heating value, Thermogravimetric Analysis (TGA), and lignocellulose content were determined for the biomass samples. The thermochemical conversion of biomass to syngas was performed using a downdraft gasifier operated at equivalence ratio 0.3. The results showed that the biomass was rich in carbon (content ranging from 44.77 to 58.54%) making it suitable for use as a solid fuel for gasification or combustion. The moisture contents of the biomass samples were below 10%. The contents of volatile matter in RWC and RWP were 74.40 and 75.40%, respectively. The UBC had a high fixed carbon content (50.60%) and comparatively low volatile matter (19%). The bulk densities of RWC, RWP and UBC were 193, 555 and 177 (kg/m3), respectively. The TGA showed the maximum weight loss of RWC and RWP around 400 °C, but this was at 800 °C for UBC. The higher heating values of RWC, RWP and UBC were 17.8 MJ/kg, 17.4 MJ/kg and 19.3 MJ/kg, respectively. The RWC and RWP had high cellulose and hemicellulose contents while UBC was rich in lignin. The syngas obtained from any of these biomass samples was mainly CO (10.81-22.67%) and CH4 (0.06-3.16%) with the lower heating value ranging from 2.78 to 4.72 MJ/Nm3. These results indicate that rubber wood biomass in various forms has relatively high potential for bioenergy applications via gasification, and it can help to support the renewable energy sector in Thailand.

Khalasa date palm leaf fiber as a potential reinforcement for polymeric composite materials

The circular economy (CE) proposes a closed-loop supply chain-based production system and reduces the ecological systems' negative impacts. CE proposes a paradigm shift from a linear economy to a circular economy with the principles of 3Rs: reduce, reuse, and recycle. CE applications can be a viable option for the sustainable production of polymeric composite materials by decreasing the cost and improving product lifetimes and mechanical performance. This paper explores Khalasa date palm leaf fiber (KDPLF) as a reinforcement for polymeric composite materials. To this end, it is essential to examine their morphology, material properties, chemical composition, and water uptake. The investigated fiber was obtained from the Qatar University farm. The morphology examination was carried out using scanning electron microscopy. Thermogravimetric analysis has been used to examine the thermal stability of KDPLF. Morphological examination indicates that the lumen size for Khalasa is 32.8 ± 15.9 µm. The SEM morphology of the KDPLF cross-section showed high hemicellulose content. Tensile properties revealed that Khalasa fiber had tensile strength/tensile modulus of 47.99 ± 13.58 MPa and 2.1 ± 0.40 GPa, respectively. The results are also demonstrated that high variation in the mechanical properties and morphology was showed in KDPLF. Water uptake has significant effects on the properties of KDPLF/epoxy composite. Accordingly, as the moisture absorption of KDPLF/epoxy increases, its strength and stiffness decrease. As the moisture absorption of KDPLF/epoxy increases, its toughness increases.

Lower temperature hydrothermal pretreatment improves the anaerobic digestion performance of spent cow bedding

Abstract The anaerobic digestion (AD) performance of spent cow bedding was investigated with different hydrothermal pretreatment (HP) conditions. Spent cow bedding was pretreated with low temperatures (50, 70, and 90°C) and different pretreatment times (2-72 h) with ammonia and without ammonia. The results showed that spent cow bedding was a good raw material for AD. After pretreatment, the concentration of volatile fatty acids (VFAs) in the group of hydrothermal pretreatments with ammonia (HPA) was higher than that in the HP group at the same pretreatment temperature and time. The optimal pretreatment condition was achieved with an HPA of 50℃ holding for 72h. At the optimal condition, the highest concentration of VFAs was 1.58-10.85 times higher than that of the other pretreated groups. The highest hemicellulose and lignin removal rates were 58.07% and 10.32%, respectively. The highest methane yield was 163.0 ml·(g VS)-1, which was 48.9% higher than that of the untreated group. The VFAs, pH, and reducing sugars showed positive relationships with the methane yield. Therefore, HP at low temperature can enhance the AD performance of spent cow bedding.

Optimization and kinetics of glucose production via enzymatic hydrolysis of mixed peels

The optimization and kinetics of glucose production via enzymatic hydrolysis of mixed peels were carried out. The substrate was characterized using proximate analysis and hydrolysis. The process was optimized using response surface methodology while the kinetics of the hydrolysis was studied using Michealis-menten model. The results obtained showed that the mixed peels have high hemicellulose content, hydrolysable carbohydrate and cellulose. The optimum conditions for glucose yield of 79% by enzymatic hydrolysis are temperature of 36 °C, time of five days, pH of 4.55 and enzyme dosage of 0.428 g/50 mL. Enzymatic hydrolysis obeyed Michealis-Menten kinetic model with spontaneous and feasible reactions. Therefore, the results have proved that mixed peels (cassava and potato peels) is a good substrate for glucose production and study of other waste peels as feed-stock is recommended.

Effect of sequential pretreatment combinations on the composition and enzymatic hydrolysis of hazelnut shells

Hazelnut shells, a high lignin containing biomass, were subjected to individual and sequential liquid hot water (LHW), alkaline (AP) and dilute acid pretreatments (DAP). Among the single pretreatments, LHW demonstrated the highest cellulose recovery of 98.1%, DAP resulted in the highest hemicellulose solubilization of 56.0%, and AP of the highest lignin removal of 49.6%. Employing two-step pretreatment on hazelnut shells, in general, demonstrated an enhanced action of the second pretreatment; therefore, the sequence of the pretreatment methods had a significant impact on both substrate characteristics and enzymatic hydrolysis efficiency of biomass. In terms of delignification, AP-LHW achieved 60.7% lignin removal, while LHW-DAP showed the highest hemicellulose removal of 93.8% and DAP-LHW resulted in the highest cellulose recovery of 94.0%. Structural properties of raw and pretreated hazelnut shells were observed by FTIR. The maximum glucose recovery of 54.9% was observed in DAP-LHW pretreated samples. For this pretreatment combination, almost 1.8 MJ total energy was required to recover 10.2 g glucose. The findings indicated that complete removal of the physical barrier of lignin and hemicellulose might not be essential; partial relocation of lignin and alteration of cellulose structure may also be efficient in increasing the sugar recovery from the lignocellulosic biomass.

Ozonolysis of wheat bran in subcritical water for enzymatic saccharification and polysaccharide recovery

The destarched wheat bran was pretreated with ozonolysis, subcritical water (SW), and their combinations to improve its enzymatic digestion and hemicellulose solubilization. Ozonolysis caused lignin destructions and partial leach of hemicelluloses, leading to the formation of oxalic acids. Taking advantage of these effects, the sequential combinations of ozonolysis and SW showed synergy, resulting in a 3-fold hydrolysis outcome relative to the individual SW treatment. Eventually, the combined pretreatment achieved a high hemicellulose removal (86%) and saccharification yield (85% for glucose) under a mild SW condition (160 °C for 30 min). Apart from morphological destructions, FTIR and TGA results indicated different structural changes caused by ozonolysis and SW. Hemicellulose was shown as the major factor hindering enzymatic hydrolysis. Additionally, the soluble polysaccharides generated by these pretreatments were characterized, showing that the single SW pretreatment was better for polysaccharide recovery. These findings may help to maximize the benefits of wheat bran biorefinery.

Fungal Pretreatments on Non-Sterile Solid Digestate to Enhance Methane Yield and the Sustainability of Anaerobic Digestion

Fungi can run feedstock pretreatment to improve the hydrolysis and utilization of recalcitrant lignocellulose-rich biomass during anaerobic digestion (AD). In this study, three fungal strains (Coprinopsis cinerea MUT 6385, Cyclocybe aegerita MUT 5639, Cephalotrichum stemonitis MUT 6326) were inoculated in the non-sterile solid fraction of digestate, with the aim to further (re)use it as a feedstock for AD. The application of fungal pretreatments induced changes in the plant cell wall polymers, and different profiles were observed among strains. Significant increases (p < 0.05) in the cumulative biogas and methane yields with respect to the untreated control were observed. The most effective pretreatment was carried out for 20 days with C. stemonitis, causing the highest hemicellulose, lignin, and cellulose reduction (59.3%, 9.6%, and 8.2%, respectively); the cumulative biogas and methane production showed a 182% and 214% increase, respectively, compared to the untreated control. The increase in AD yields was ascribable both to the addition of fungal biomass, which acted as an organic feedstock, and to the lignocellulose transformation due to fungal activity during pretreatments. The developed technologies have the potential to enhance the anaerobic degradability of solid digestate and untap its biogas potential for a further digestion step, thus allowing an improvement in the environmental and economic sustainability of the AD process and the better management of its by-products.

Physicochemical Characterization and SEM-EDX Analysis of Brewer’s Spent Grain from the Craft Brewery Industry

The brewing industry generates, as the primary coproduct, brewers’ spent grain (BSG). In Mexicali, Baja California, Mexico, there are 17 companies that generated 282 tons of BSG by 2016. Cattle feeding is the most common type of disposal for this waste. However, it can be valorized for the production of bioenergy or as a source of added-value products. Therefore, the objective of the present work was to assess the physicochemical properties of the brewers’ spent grain from a local craft brewery, to choose the most appropriate exploitation route. Chemical and morphological analyses were carried out by energy dispersive X-ray fluorescence spectroscopy (EDX), scanning electron microscopy, and the higher heating value determination. The results of the proximate analyses were 72.32% moisture, 78.47% volatile matter, 17.48% fixed carbon, and 4.05% ash. The results of the chemical analysis for extractables were 5.23% using organic solvent and 50.25% using hot water. The content determination were 17.13% lignin, 26.80% cellulose, and 37.17% hemicellulose. The results of the ultimate analysis were 43.59% C, 6.18% H, 3.46% N, and 37.22% O. The higher heating value experimentally obtained was 18.70 MJ/kg. Moreover, in the EDX analysis, Ca, P, K, and S were mainly found. It is recommendable to valorize the BSG through the xylitol, bioethanol or biogas production, because of its high moisture, hemicellulose and cellulose content.

A comparative study of hemicellulose isolation with hot water, alkaline, and delignification methods from tea leaf brewing waste

Tea leaf brewing waste (TLBW) is a waste with high hemicellulose content. It is a valuable waste of the pharmaceutical and cosmetics industry especially the beverage industry. In this study, the extraction of hemicelluloses (HC) from tea leaf brewing waste using three different pretreatment methods were investigated. The isolation yield of the HC was determined depending on pretreatment methods and pretreatment parameters such as the isolation temperature (25–55 °C), alkaline concentration (NaOH, 5–20%), contact time (12–24 h), the oxidative component (H2O2), and the concentration of sodium chlorite (NaCIO2) in the solution (2–10%). It was observed that the yield of isolation of hemicellulose varied between about 1 and 36% on the basis of raw materials depending on the extraction parameters. The experimental results showed that the suitable conditions for isolation of hemicellulose by alkaline pretreatment method were 15% NaOH concentration, 12-h contact time, and 45 °C. As a result of the experiments performed with the most suitable conditions, approximately 96% of the total hemicellulose in the TLBW was isolated. The extraction yield of hemicellulose achieved by the delignification process was found to be lower about 3% compared with the alkaline methods. But, the hemicellulose color achieved by the delignification process was lighter in color than the alkaline method. The results of the FTIR and H-NMR analysis show that the purity of the hemicellulosic fraction, which was obtained using the delignification method, was higher than the alkaline method.

Fascinating physical-chemical properties and fiber morphology of selected waste plant leaves as potential pulp and paper making agents

The search for non-wood fibers as alternative to the limited wood fiber resources is highly imperative in the pulp and paper-based industries. This is due to growing environmental concern as a result of excessive deforestation. This study aimed at investigating the pulp and paper potentials of pineapple crown (Ananas comosus), sandbox (Hura crepitans), pino macho (Pinus caribaea), elephant grass (Pennissetum purpureum) and teak (Tectona grandis) leaves. Chemical properties (holocellulose, cellulose, hemicellulose, ash contents, hot water and 1% NaOH solubilities) were determined using the relevant TAPPI test and chlorite methods, while the physical properties were determined after the pulping processes. Fourier transform-infrared spectroscopic (FT-IR) analyses of intrinsic functional groups of the paper sheets produced from the pulps of the waste plant leaves were determined. In addition, scanning electron microscope (SEM-EDX) analyses of the morphological characteristic and elemental compositions of the resulting hand sheet surfaces were also examined. P. caribaea has the highest lignin (80.22 ± 0.012%) and cellulose (72.30 ± 0.012%) contents with lowest 1% NaOH solubility (15.20 ± 0.05%) values. A .comosus has the highest hemicellulose (21.73 ± 0.1%) and moisture (75.00 ± 0.12%) contents with lowest ash values (5.01 ± 0.15%). The fibre lengths and the Runkel ratio of the resulting pulps were of the order, A. comosus > P. purpureum > P. caribaea > H. crepitans > T. grandis and A. comosus < P. caribaea < H. crepitans < T. grandis < P. purpureum respectively. Their surface morphologies, paper qualities and characteristics differ, but comparable with the earlier reported literatures on the pulps from wood and non-woody sources.

Energy and life cycle impact assessment for xylitol production from corncob

The conversion of biobased feedstocks into energy and value-added chemicals is one main approach to address the current global challenge for waste mitigation through the biorefinery mode. Corncob biomass which is one of the most abundant agricultural residue in India with a high hemicellulose content, can serve as a potential low-cost raw material for food-grade xylitol production. The present study demonstrates a process for xylitol production from corncob biomass with detailed energy and life cycle analysis for viability assessment. The major highlight of the process is the use of microbial fermentation, where biomass-derived D-xylose is converted to xylitol with high selectivity. Overall, 0.502 kg of xylitol crystals could be produced from 3.5 kg of corncob biomass. Simulation analysis revealed that the evaporators are the primary consumers of energy, and the process of heat integration can significantly reduce the energy requirements of the overall process. Environmental impacts of the system evaluated showed emission results of 8.68 kg CO2 equivalent and revealed that marine aquatic and freshwater eco-toxicity are the only possible contributors to the environment. The results suggest that the process would have favourable energy balances, which can be used in pilot plant and heat exchanger network design and operation for xylitol production scale up to 500 L.

Synthesis of Carboxymethyl Cellulose Form Banana Stems and its Characterization for Anode Binder of Li-Ion Battery

Banana (Musa acuminate) is one of the important fruit crop cultivated in Indonesia. Banana stems is waste biomass form banana farming which the amount is very abundant. Recently, the banana stems waste was used for animal feed, but the amount is small, mostly goes as waste. Banana stems have a high cellulose and hemicellulose content, more than 60%, which made it useful for row material of Carboxymethyl Cellulose (CMC). In this paper, we synthesized CMC from banana stems and apply it as binder in the electrodes of lithium ion battery. The steps of synthesizing CMC from banana stems started with the isolation of the cellulose, then followed by the processes of alkalization, carboxymethylation and finally the purification. FTIR spectrum shows the absorption bands at 3427 cm-1, 2928 cm-1, 1613 cm-1 and 1420 cm-1 which indicated the successfully of CMC synthesized. The presence of strong absorption bands at 1613 cm-1 and 1420 cm-1 are related to the stretching vibration of the carboxyl group (COO-) and (COO-Na). The peak absorption at around 2928 cm-1 is due to stretching vibration of all hydrocarbon constituent in CMC. While the broad absorption around 3427 cm-1 is due to the stretching vibration of the hydroxyl groups (-OH). The purity test of CMC mesh-100 is resulting the purity values of 99.84%. These results prove that CMS has actually been formed with high purity. In the application of CMC as anode binder, the best composition is 3 % CMC, where it gives the highest conductivity of 0.457 S/cm. Voltammogram cyclic measurement with a scan rate of 50 mV/s in the voltage range of -1.2 to 1.2 Volt gives the capacitance value of 18 mF.

Wheat straw components fractionation, with efficient delignification, by hydrothermal treatment followed by facilitated ethanol extraction

Lignocellulosic biomass fractionaion into its three major components is critically important for efficient feedstock utilization. The hydrothermal-ethanol method has broad application as its first step, hydrothermal treatment, provides high hemicellulose separation efficiency. However, it severely inhibits the delignification on the subsequent ethanol extraction. In this study, the second step, ethanol extraction, was facilitated by the addition of 3% NaOH and 3% H2O2, resulting in a significant improvement of lignin separation (by 48.2%). SEM, AFM, XPS, and XRD were used to characterize the surface composition of the remaining solids (crude cellulose) while the structure of isolated lignin was characterized by FT-IR, CP/MAS 13C NMR, GPC and TGA. The lignin samples isolated with both facilitated and non-facilitated ethanol extraction were compared to elucidate the lignin removal mechanism. The results showed that lignin degradation and crosslinking/polymerization occur in parallel during both the hydrothermal treatment and ethanol extraction.

Valorization of apple pomace using bio-based technology for the production of xylitol and 2G ethanol.

Apple pomace was studied as a raw material for the production of xylitol and 2G ethanol, since this agroindustrial residue has a high concentration of carbohydrate macromolecules, but is still poorly studied for the production of fermentation bioproducts, such as polyols. The dry biomass was subjected to dilute-acid hydrolysis with H2SO4 to obtain the hemicellulosic hydrolysate, which was concentrated, detoxified and fermented. The hydrolyzate after characterization was submitted to submerged fermentations, which were carried out in Erlenmeyer flasks using, separately, the yeasts Candida guilliermondii and Kluyveromyces marxianus. High cellulose (32.62%) and hemicellulose (23.60%) contents were found in this biomass, and the chemical hydrolysis yielded appreciable quantities of fermentable sugars, especially xylose. Both yeasts were able to metabolize xylose, but Candida guilliermondii produced only xylitol (9.35gL-1 in 96h), while K. marxianus produced ethanol as the main product (10.47gL-1 in 24h) and xylitol as byproduct (9.10gL-1 xylitol in 96h). Maximum activities of xylose reductase and xylitol dehydrogenase were verified after 24h of fermentation with C. guilliermondii (0.23 and 0.53U/mgprot, respectively) and with K. marxianus (0.08 e 0.08U/mgprot, respectively). Apple pomace has shown potential as a raw material for the fermentation process, and the development of a biotechnological platform for the integrated use of both the hemicellulosic and cellulosic fraction could add value to this residue and the apple production chain.

Harnessing the potential of common water hyacinth as an industrial raw material for the production of quality biofuel briquettes

Eichhornia crassipes has a high cellulose and hemicellulose content, which are easily converted to simple sugars, thus making the plant suitable for the production of biofuel briquettes. The main purpose of this proposed work, therefore, was to investigate the production of bio briquettes from E. crassipes. The plant was harvested from a wastewater effluent management system, chopped, sun-dried and pulverized to a particle size of < 5 mm and mixed with various binders (Eucalyptus globulus leaves powder, molasses and phytoplankton scum). The binders were appropriately prepared and added to E. crassipes at the ratios of 10%, 20% and 30%. The quality of biofuel briquettes was evaluated using compressed density, relaxed density, water resistance, durability and calorific values (CV) parameters and compared to those of charcoal briquettes already on the market. The results showed a water resistance capacity of 45%, relaxation ratios of between 1.08 and 1.33, CV of 1148.35 kJ/kg for 20% molasses-based briquettes, CV of 1090.43 kJ/kg for 20% E. globulus leaf-based briquettes and CV of 1422.97 kJ/kg for charcoal-based briquettes. In conclusion, therefore, E. crassipes may become a viable raw material for producing quality biofuel briquettes that are durable with the desired calorific value and may be able to withstand mechanical handling and be useful for household and cottage industries locally.

Characterization of composite material from the copolymerized polyphenolic matrix with treated cassava peels starch

Conventional binders in the particleboards formulation involve use of formaldehyde resins. Epidemiologic studies show that formaldehyde is carcinogenic. Efforts to reduce formaldehyde emissions by use of scavengers has not been proven to reduce the emission. Molecular bonding of biobased adhesive molecules with lignocellulose materials provides an alternative way of producing composite material. In this study, maize stalk (MS), rice husks (RH) and sugarcane bagasse (SB) were used as sources of lignocellulose materials for particleboard formulation. SB, MS and RH were collected from their respective sites, sorted and dried. MS and RH were ground. Lignin content determination was done by drying lignocellulose material at 105 °C. Lignocellulose materials were prepared by hydrolysis of dried lignocellulose material with sodium hydroxide. Oxidized starch was prepared by oxidation of cassava peel starch using alkaline hydrogen peroxide. Particleboards were formulated through starch-lignocellulose polymerization at 60 °C compressed with 6.5 Nmm−2 pressure. Characterization of raw materials and formulated particleboards was done using XRD for mineralogical analysis, FTIR and NMR for elucidation of functional groups transformation. The results showed that esterification is the main process of chemical bonding in the particleboard formulation due to reaction between –COOH from starch and and OH- from lignocellulose. Etherification between hydroxyl groups from starch with hydroxyl groups from lignocellulose material. RH combined more through silication process with cassava peels starch than RH and SB showing materials containing high cellulose and hemicellulose content are more compatible. Composite materials formulated were used to produce medium density particleboards that can be used for making furniture and room partitioning.

Fibrillation and characterization of lignin-containing neutral sulphite (NS) pulps rich in hemicelluloses and anionic charge

The potential of neutral sulphite pulps from softwood with different yields (c. 58–84%) and high residual lignin contents (c. 10–25 wt%) was investigated as a raw material for lignin-containing cellulose nanofibrils (LCNFs) by following their fibrillation during grinding. It was found that the lower yield (58–65%) pulps needed two grinding cycles to produce fibrillated fibers with water retention values (WRV) as high as 400 g/g (at the energy consumption level of 1400 kWh/t). In contrast, the high yield (77–84%) pulps fibrillated more slowly, requiring five grinding cycles to reach comparable WRV values. Apparently, higher crosslinking degrees of lignin in the high yield pulps are hampering the fibrillation, although the high hemicellulose contents (21–24 wt%) and the high charge densities (200–350 µmol/g, originating from carboxylic and sulphonic acid groups) of the pulps were expected to enhance the fibrillation. Nevertheless, regardless of the different fibrillation behaviour, most of the pulps formed c. 10–15% of nanosized material below 30 nm and significant amounts of fibrils with size under 100 nm based on the centrifugation method and FE-SEM images. As the pulps were of moderate to high yield and fibrillated easily without any chemical or enzymatic pretreatments, they show promise for cost-efficient production of LCNFs. The nanopapers prepared from the fibrillated pulps showed tensile strengths (73–125 MPa) comparable with the nanopapers from high yield mechanical pulps, whereas the water contact angles (41°–58°) were closer the those of chemical pulps.

Acetylation of lignin containing microfibrillated cellulose and its reinforcing effect for polylactic acid

High hemicellulose and lignin content MFC (MFLC) was isolated from chemi-thermomechanical pulp (CTMP), and surface acetylation used to significantly decrease its polarity. This modification of MFLC provided good dispersibility in PLA when used for biocomposites fabrication via a solvent casting method. MFLC exhibited higher modification efficiency compared to lignin-free MFC. Base-catalysed surface acetylation unchanged the crystalline structure of MFLC. Detection of the hydrogen bond between acetylated MFLC (Ac-MFLC) and PLA confirmed its role in improvement of the mechanical performance, thermal properties and crystallinity of the biocomposite with Ac-MFLC acting as an effective reinforcing and nucleating agent. The approach confirms the suitability of surface functionalization of MFLC for fabrication of biocomposites for a wide range of applications such as packaging and biomedical products.