Lignin preparation from oil palm empty fruit bunches by sequential acid/alkaline treatment--A biorefinery approach

Fumaric acid production from fermented oil palm empty fruit bunches using fungal isolate K20: a comparison between free and immobilized cells

This study investigated the potential of using steam-exploded oil palm empty fruit bunches (EFB) as a renewable feedstock for producing fumaric acid (FA), a food additive widely used for flavor and preservation, through a separate hydrolysis and fermentation process using the fungal isolate K20. The efficiency of FA production by free and immobilized cells was compared. The maximum FA concentration (3.25 g/L), with 0.034 g/L/h productivity, was observed after incubation with the free cells for 96 h. Furthermore, the production was scaled up in a 3-L air-lift fermenter using oil palm EFB-derived glucose as the substrate. The FA concentration, yield, and productivity from 100 g/L initial oil palm EFB-derived glucose were 44 g/L, 0.39 g/g, and 0.41 g/L/h, respectively. The potential for scaling up the fermentation process indicates favorable results, which could have significant implications for industrial applications.

Acetylated lignin from oil palm empty fruit bunches and its electrospun nanofibres with PVA: Potential carbon fibre precursor

The electrospinning of acetylated lignin/polyvinyl alcohol (PVA) nanofibres was carried out to expand the application of lignin materials obtained from oil palm empty fruit bunches (OPEFB). Lignin was isolated by the steam explosion method and subsequently precipitated using H₂SO₄. Acetylated lignin was produced by mixing acetic anhydride and pyridine at a 2:1 v/v ratio. Following the acetylation process, FTIR analysis showed the absorption of the C=O carbonyl group at wavenumber 1714.6 cm^-1. The chemical structures of isolated and acetylated lignin were established using ¹H NMR spectral analysis, and XRD examination demonstrated their amorphous character. The electrospinning process of acetylated lignin and PVA solution was then carried out at 15 kV voltage, 0.8 mL/h flow rate, and 12 cm distance between the needle and collector. The sample exhibited electrical conductivity of 443 μS/cm and viscosity of 2.8 × 10^-3 Pa s. The morphology analysis showed that there were more beads on the surface of lignin/PVA nanofibres than acetylated lignin/PVA nanofibres. In addition, acetylated lignin/PVA nanofibre was more stable than lignin/PVA. The G-band of carbonized material increased with the presence of lignin. The works presented suggest the potential of using waste materials such as OPEFB as a suitable precursor for the preparation of carbon fibre.

Lignocellulosic Biorefinery Technologies: A Perception into Recent Advances in Biomass Fractionation, Biorefineries, Economic Hurdles and Market Outlook

Lignocellulosic biomasses (LCB) are sustainable and abundantly available feedstocks for the production of biofuel and biochemicals via suitable bioconversion processing. The main aim of this review is to focus on strategies needed for the progression of viable lignocellulosic biomass-based biorefineries (integrated approaches) to generate biofuels and biochemicals. Processing biomass in a sustainable manner is a major challenge that demands the accomplishment of basic requirements relating to cost effectiveness and environmental sustainability. The challenges associated with biomass availability and the bioconversion process have been explained in detail in this review. Limitations associated with biomass structural composition can obstruct the feasibility of biofuel production, especially in mono-process approaches. In such cases, biorefinery approaches and integrated systems certainly lead to improved biofuel conversion. This review paper provides a summary of mono and integrated approaches, their limitations and advantages in LCB bioconversion to biofuel and biochemicals.

Agri-Biodegradable Mulch Films Derived from Lignin in Empty Fruit Bunches

Mulch films increase soil temperature, maintain soil moisture, improve water and fertilizer absorption, and reduce weed growth. This work studied a mulching film made using polyvinyl alcohol (PVA) and lignin extracted from empty fruit bunches (EFBs). The mulch films were investigated for opaqueness, biodegradation, water-solubility, absorption, and mechanical properties. Life cycle assessment (LCA) and cost estimate analysis were conducted. The composite mulch film-PVA solution was blended with 6% EFB lignin in dimethyl sulfoxide (DMSO) solution using five different amounts (0, 20, 40, 60, or 80 wt% lignin). The results showed that increasing the amount of lignin increased the film’s water solubility, moisture content, and biodegradability. At the same time, water absorption tended to decrease. Consequently, the light transmittance of the film was reduced, which had a positive effect on preventing soil weed growth. Tests of the mechanical properties showed that 60% lignin in the PVA film had the highest tensile strength (16.293 MPa). According to the LCA studies and cost estimation, the lignin-mixed PVA film had the lowest impact and was cheaper than the commercial mulching film. The results suggested that it is possible to blend polyvinyl alcohol polymer with lignin to improve biodegradability up to 25.47% by soil burial and 32% by water solubility.

Simultaneous Saccharification and Fermentation of Empty Fruit Bunches of Palm for Bioethanol Production Using a Microbial Consortium of S. cerevisiae and T. harzianum

A simultaneous saccharification and fermentation (SSF) optimization process was carried out on pretreated empty fruit bunches (EFBs) by employing the Response Surface Methodology (RSM). EFBs were treated using sequential acid-alkali pretreatment and analyzed physically by a scanning electron microscope (SEM). The findings revealed that the pretreatment had changed the morphology and the EFBs’ structure. Then, the optimum combination of enzymes and microbes for bioethanol production was screened. Results showed that the combination of S. cerevisiae and T. harzianum and enzymes (cellulase and β-glucosidase) produced the highest bioethanol concentration with 11.76 g/L and a bioethanol yield of 0.29 g/g EFB using 4% (w/v) treated EFBs at 30 °C for 72 h. Next, the central composite design (CCD) of RSM was employed to optimize the SSF parameters of fermentation time, temperature, pH, and inoculum concentration for higher yield. The analysis of optimization by CCD predicted that 9.72 g/L of bioethanol (0.46 g/g ethanol yield, 90.63% conversion efficiency) could be obtained at 72 h, 30 °C, pH 4.8, and 6.79% (v/v) of inoculum concentration using 2% (w/v) treated EFBs. Results showed that the fermentation process conducted using the optimized conditions produced 9.65 g/L of bioethanol, 0.46 g/g ethanol yield, and 89.56% conversion efficiency, which was in close proximity to the predicted CCD model.

Response surface methodology (RSM) and artificial neural network (ANN) approach to optimize the photocatalytic conversion of rice straw hydrolysis residue (RSHR) into vanillin and 4-hydroxybenzaldehyde

Effective use of waste lignin is always a challenging task, technologies have been applied in the past to get value-added compounds from waste lignin. However, the existing technologies are not economical and efficient to produce the value-added chemicals. Alkali soluble lignin from rice straw hydrolysis residue (RSHR) is subjected to photocatalytic conversion into value-added compounds. Photocatalysis is one of the multifarious advanced oxidation processes (AOPs), carried out with TiO2 nanoparticles under a 125 W UV bulb. Gas chromatography mass spectroscopy (GCMS) confirmed the formation of vanillin and 4-hydroxybenzaldehyde. RSM and ANN techniques are adopted to optimize the process conditions for the maximization of the products. The response one (Y 1) vanillin (24.61 mg) and second response (Y 2) 4-hydroxybenzaldehyde (19.51 mg) is obtained at the optimal conditions as 7.0 h irradiation time, 2.763 g/L catalyst dose, 15 g/L lignin concentration, and 14.26 g/L NaOH dose for alkali treatment, suggested by face-centered central composite design (CCD). RSM and ANN models are statistically analyzed in terms of RMSE, R 2 and AAD. For RSM the R 2 0.9864 and 0.9787 while for ANN 0.9875 and 0.9847, closer to one warrant the good fitting of the models. Therefore, in terms of higher precision and predictive ability of both models the ANN model showed excellence for both responses as compared to the RSM model.

Optimization of ethanol-extracted lignin from palm fiber by response surface methodology and preparation of activated carbon fiber for dehumidification

Lignin is a renewable bioresource that can be used for a variety of value-added applications. However, the effective separation of lignin from lignocellulosic biomass remains an ongoing challenge. In this study, lignin was extracted from waste palm fiber and successfully converted into a dehumidifying material. The following four process parameters of lignin extraction from palm fiber were optimized systematically and comprehensively using the response surface methodology: reaction time, extraction temperature, ethanol concentration and solid/liquid ratio. The results revealed that under the optimum processing conditions (111 min of extraction at 174 °C using 73% ethanol at 1/16 g/mL solid/liquid ratio), the extraction yield of lignin was 56.2%. The recovery of ethanol solvent was as high as 91.8%. Further, the lignin could be directly used without purification to produce lignin-based activated carbon fibers (LACFs) with specific surface area and total pore volume of 1375 m2/g and 0.881 cm3/g, respectively. Compared with the commercial pitch-based activated carbon fiber, the LACF has a higher specific area and superior pore structure parameters. This work provides a feasible route for extracting lignin from natural palm fiber and demonstrates its use in the preparation of activated carbon fiber with a remarkable performance as a solid dehumidification agent.

A non-waste strategy for enzymatic hydrolysis of cellulose recovered from domestic wastewater

Cellulose is a potential resource to be recovered from wastewater treatment plants (WWTP). Enzyme formulations can be employed to hydrolyze cellulose into fermentable sugars, to be further used as biochemical building blocks or reducing its recalcitrance to further treatment processes. This study proposed the production, recovery and formulation of cellulase using domestic wastewater as culture medium and its application for the hydrolysis of cellulosic residues recovered from WWTPs. Cellulose was recovered from raw sanitary wastewater using a fine-mesh sieve (0.35 mm) and quantified through enzymatic hydrolysis and thermogravimetric analysis. The production, concentration and formulation of cellulase enzyme resulted in an enzymatic blend of endoglucanases (7.3 U_FP/mL), cellobiohydrolases (7.4 U_CMC/mL) and beta-glucosidases (4.4 U_BGL/mL). The content of the recovered cellulosic material was 21.3% according to enzymatic hydrolysis and 27.7 for thermogravimetric results. The enzymatic hydrolysis of the WWTP residue using the produced cellulase (107.6 ± 10.2 mg_reduc/g_residue) showed better results than using the commercial cellulase complex (66.4 ± 2.5 mg_reduc/g_residue). This fact showed the potential of application of the produced enzyme for the hydrolysis of cellulosic residues recovered from WWTP processes. In a non-waste biorefinery approach, the generated hydrolysate can be further used for producing added-value biomolecules including biofuels and biochemicals.

Performance of Citric Acid-Bonded Oriented Board from Modified Fibrovascular Bundle of Salacca (Salacca zalacca (Gaertn.) Voss) Frond

The fibrovascular bundle (FVB) in palm plants consists of fiber and vascular tissue. Geometrically, it is a long fiber that can be used as an oriented board raw material. This research aimed to examine the performance of citric acid-bonded orientation boards from modified FVB salacca frond under NaOH + Na₂SO₃ treatment and the bonding mechanism between the modified FVB frond and citric acid. The results showed that changes in the chemical composition of FVB have a positive effect on the contact angle and increase the cellulose crystallinity index. Furthermore, the mechanical properties of the oriented board showed that 1% NaOH + 0.2% Na₂SO₃ with 60 min immersion has a higher value compared to other treatments. The best dimension stability was on a board with the modified FVB of 1% NaOH + 0.2% Na₂SO₃ with 30 and 60 min immersion. The bonding mechanism evaluated by FTIR spectra also showed that there is a reaction between the hydroxyl group in the modified FVB and the carboxyl group in citric acid. This showed that the modified combination treatment of NaOH+Na₂SO₃ succeeded in increasing the mechanical properties and dimensional stability of the orientation board from the FVB salacca frond.

A biorefinery approach for enzymatic complex production for the synthesis of xylooligosaccharides from sugarcane bagasse

The use of low-cost feedstock for enzyme production is an environmental and economic solution. Sugarcane bagasse and soybean meal are employed in this study for optimised xylanase production with the concomitant synthesis of proteases. The enzymatic complex is produced by submerged fermentation by Aspergillus niger. Optimisation steps lead to a 2.16-fold increase in enzymatic activity. The fermentation kinetics are studied in Erlenmeyer flasks, a stirred tank reactor and a bubble column reactor, with the xylanase activities reaching 52.9; 33.7 and 60.5 U.mL^-1, respectively. The protease production profile is also better in the bubble column reactor, exceeding 7 U.mL^-1. The enzyme complex is then evaluated for the synthesis of xylooligosaccharides from sugarcane extracted xylan with a production of 3.1 g.L^-1 where xylotriose is the main product. Excellent perspectives are observed for the developed process with potential applications in the animal feed, prebiotics and paper industries.

Biosynthesis of Commodity Chemicals From Oil Palm Empty Fruit Bunch Lignin

Lignin is one of the most abundant natural resources that can be exploited for the bioproduction of value-added commodity chemicals. Oil palm empty fruit bunches (OPEFBs), byproducts of palm oil production, are abundant lignocellulosic biomass but largely used for energy and regarded as waste. Pretreatment of OPEFB lignin can yield a mixture of aromatic compounds that can potentially serve as substrates to produce commercially important chemicals. However, separation of the mixture into desired individual substrates is required, which involves expensive steps that undermine the utility of OPEFB lignin. Here, we report successful engineering of microbial hosts that can directly utilize heterogeneous mixtures derived from OPEFB lignin to produce commodity chemicals, adipic acid and levulinic acid. Furthermore, the corresponding bioconversion pathway was placed under a genetic controller to autonomously activate the conversion process as the cells are fed with a depolymerized OPEFB lignin mixture. This study demonstrates a simple, one-pot biosynthesis approach that directly utilizes derivatives of agricultural waste to produce commodity chemicals.

Lignin from oil palm empty fruit bunches: Characterization, biological activities and application in green synthesis of silver nanoparticles

Lignin was extracted from oil palm empty fruit bunches under four different conditions. The lignin samples were characterized and employed in the green synthesis of silver nanoparticles. Two-dimensional HSQC NMR analysis showed that lignins extracted under more aggressive conditions (3.5% acid, 60 min) exhibited less signals and thus, presented a more degraded chemical structure. Additionally, those lignins obtained under harsh conditions (3.5% acid, 60 min) exhibited higher antioxidant capacity than those obtained under mild conditions (1.5% acid, 20 min). Formation of lignin-mediated silver nanoparticles was confirmed by color change during their synthesis. The surface plasmon resonance peaks (423-427 nm) in UV-visible spectra also confirmed the synthesis of AgNPs. AgNPs showed spherical shape, polycrystalline nature and average size between 18 and 20 nm. AgNPs, in suspension, presented a negative Zeta potential profile. Lignin was assumed to contribute in the antioxidant capacity exhibited by AgNPs. All AgNPs presented no significant differences on the disk diffusion antimicrobial susceptibility test against E. coli. The minimum inhibitory concentration of HAL3-L AgNPs (62.5 μg·mL^-1) was better than other physicochemically produced AgNPs (100 μg·mL^-1).

Effect of sequential acid-alkaline treatment on physical and chemical characteristics of lignin and cellulose from pine (Pinus spp.) residual sawdust

Timber industry generates large amounts of residues such as sawdust. Softwoods have a significant economic value for timber production and the Pinus genus is widely utilized. Thus, the aim of this work was to study the hemicellulose extraction and lignin recovery from pine (Pinus spp.) residual sawdust (PRS) by sequential acid-alkaline treatment, generating a cellulose-rich solid fraction. The hemicellulose removed was 87.11% (wt·wt^-1) after dilute acid treatment at 130 °C, 4.5% (wt·wt^-1) of H₂SO₄ for 20 min at 120 rpm. Three temperatures were evaluated for recovering the lignin and the highest yield, 93.97% (wt·wt^-1), was achieved at 170 °C, 10% (wt·wt^-1) of NaOH for 90 min at 120 rpm. Lignin was characterized by Fourier-transform infrared spectroscopy, nuclear magnetic resonance and thermogravimetry. The resulting cellulose-rich fraction exhibited polymorphic transformation. The results demonstrated that PRS is a promising lignocellulosic residue whose lignin and carbohydrates can be readily obtained.

Physical Properties of Carboxymethyl Cellulose from Palm Bunch and Bagasse Agricultural Wastes: Effect of Delignification with Hydrogen Peroxide

The aim of this work was to synthesize carboxymethyl cellulose (CMC) and produce CMC films from the cellulose of palm bunch and bagasse agricultural waste. The effect of various amounts of H₂O₂ (0-40% v/v) during delignification on the properties of cellulose, CMC, and CMC films was studied. As the H₂O₂ content increased, yield and the lignin content of the cellulose from palm bunch and bagasse decreased, whereas lightness (L*) and whiteness index (WI) increased. FTIR confirmed the substitution of a carboxymethyl group on the cellulose structure. A higher degree of substitution of CMC from both sources was found when 20%-30% H₂O₂ was employed. The trend in the L* and WI values of each CMC and CMC film was related to those values in their respective cellulose. Bleaching each cellulose with 20% H₂O₂ provided the cellulose with the highest viscosity and the CMC films with the greatest mechanical (higher tensile strength and elongation at break) and soluble attributes, but the lowest water vapor barrier. This evidence indicates that cellulose delignification with H₂O₂ has a strong effect on the appearance and physical properties of both CMCs.

Delignification of Pinecone and Extraction of Formic Acid in the Hydrolysate Produced by Alkaline Fractionation

The objectives of our research are to investigate the concept of delignification from pinecone through alkaline fractionation and then extraction of formic acid from the hydrolysate through esterification using ethanol. The pinecone is considered a promising material because of its relatively higher lignin content (35.80%) than other lignocellulosic biomass. The recovery yield of acid insoluble lignin (AIL) reached its maximum value of 79.20% at 8% NaOH, and the concentration of formic acid in the hydrolysate had its highest value under the same conditions. Moreover, the glucan content in fractionated solid remained high. The hydrolysate was subjected to esterification with ethanol under various reaction conditions for formic acid extraction, with solvent mixing ratio range: 1:1-1:4 v/v, reaction temperature range: 30-45 °C, and reaction time range: 60-100 min. Subsequently, the ethanol mixture (ethanol and ethyl formate) was recovered through distillation. The formic acid was extracted with more than 85% at mixing ratio of 1:2 and 45 °C for all reaction times. Furthermore, salt compounds composed mainly of Na and S were recovered because of its properties not soluble in ethanol solution.

Utilization of chemically treated cashew-nut shell as potential adsorbent for removal of Pb(II) ions from aqueous solution

In this study, cashew nut shells (CNS), waste from a cashew nut processing factory, have been used as an adsorbent for Pb(II) ions in water. Treatments of CNS with 1 M of H₂SO₄, HNO_3, and NaOH solutions were performed to modify their surfaces and improve their adsorption capacities. Characterization of untreated and chemical-treated CNS was carried out using nitrogen adsorption isotherm, elemental (CHN) analysis, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX). In the study of Pb(II) removal, various models of adsorption kinetics and isotherms were evaluated against the experimental data. The results showed that H₂SO₄-treated CNS exhibited the highest adsorption capacity. The chemical treatment removes impurities, alters the surface functional groups and improves specific surface areas and pore volumes of native CNS significantly. Surface adsorption and intra-particle diffusion steps were found to substantially affect the overall adsorption process of Pb(II) on H₂SO₄-treated CNS. Owing to its easy preparation and comparable adsorption capacity, H₂SO₄-treated CNS has the potential to be developed as a low-cost adsorbent for the removal of Pb(II) from contaminated water.

Production and characterization of lignin and cellulose fractions obtained from pretreated vine shoots by microwave assisted alkali treatment

This work deals with the optimization of the second stage of a biorefinery scheme to separate simultaneously cellulose and lignin from hydrothermally pre-treated vine shoots. For this, the suitability of the microwave-assisted alkaline delignification was assessed and optimized through a Box-Wilson experimental design. The optimum conditions (150 °C, 6 wt% NaOH, 30 min) allowed maximizing the lignin removal (82 wt%) and minimizing the loss of the cellulose (35 wt%) present in the pre-treated vine shoots. A thorough characterization of the two fractions obtained at optimum conditions was performed: the cellulose rich solid was analyzed by XRD and FTIR and the lignin was subjected to HPSEC, Py/GC-MS, ¹³C- and ¹H NMR. This purposed second stage would allow performing an integral biorefinery with low energy requirements and environmentally friendly conditions. This approach aligns with the circular economy and the zero waste production philosophies, promoting the sustainable development.

OrganoCat Fractionation of Empty Fruit Bunches from Palm Trees into Lignin, Sugars, and Cellulose-Enriched Pulp

The palm oil industry produces large amounts of empty fruit bunches (EFB) as waste. EFB are very recalcitrant toward further processing, although their valorization could create novel incentives and bio-economic opportunities for the industries involved. Herein, EFB have been successfully subjected to the OrganoCat pretreatment-using 2,5-furandicarboxylic acid as the biogenic catalyst-to fractionate and separate this lignocellulosic material into its main components in a single step. The pretreatment of EFB leads to the deacetylation and depolymerization of noncellulosic polysaccharides and to the partial delignification of the cellulosic fiber. The OrganoCat processing of EFB yielded 45 ± 0.5 wt % cellulose-enriched pulp, 20 ± 0.7 wt % extracted lignin, 3.8 ± 0.2 wt % furfural, and 11 ± 0.6 wt % hydrolyzed sugars. The obtained EFB-pulp showed high accessibility to cellulases, resulting in a glucan conversion of 73 ± 2% after 72 h (15 ± 2% after 1 h) with commercial cellulase cocktail (Accellerase 1500). Overall, the results suggest that the treatment of the EFB material using OrganoCat may create promising paths for the full valorization of EFBs.

Pulp improvement of oil palm empty fruit bunches associated to solid-state biopulping and biobleaching with xylanase and lignin peroxidase cocktail produced by Aspergillus sp. LPB-5

Oil palm empty fruit bunches is a lignocellulosic feedstock with biotechnological potential and thousands of tons are generated in the world each year. Filamentous fungi producing xylanases and ligninases in biopulping to obtain cellulose is a pulp improvement alternative. The enzymatic cocktail was produced in solid-state biopulping by Aspergillus sp. LPB-5 with 54.32 U/g xylanase, 13.41 U/g lignin peroxidase and low cellulase activity. Biological, thermal and chemical pretreatments were compared and enzymatic biobleaching was applied to pretreated pulps. Biopulping and biobleaching combination had 36.80% lignin loss, 26.27% hemicellulose reduction, 74.36% pulp yield with 36.56% digestibility. Alkaline and biobleaching combination removed 81.97% hemicellulose and 93.89% lignin with 73.59% digestibility. Enzymatic biobleaching increased the pulp digestibility in all pretreatments. Finally, the development of a bio-pretreatment to remove hemicellulose and alter the lignin-carbohydrate complex interface presented a soft process with great eco-friendly potential, where mild pre-treatments would reduce the use of aggressive agents.

Treatment of Coffee Husk with Ammonium-Based Ionic Liquids: Lignin Extraction, Degradation, and Characterization

Four ammonium-based ionic liquids were synthesized for the selective extraction and degradation of lignin from coffee husk. The extracted lignin samples were characterized by Fourier transform infrared, gel permeation chromatography, gas chromatography-mass spectrometry, UV-vis, ¹H and ¹³C NMR, heteronuclear single-quantum coherence-NMR, thermogravimetric analysis, X-ray diffraction, and field emission scanning electron microscopy analyses. The analyzed results confirmed that these ionic liquids are able to effectively extract and decompose the lignin to smaller molecules from the biomass. Experimental results show that a significantly high yield, 71.2% of the original lignin, has been achieved. This processing method is an efficient, economical, and environmentally friendly green route for producing high-added-value lignin from wasted coffee husk.

Thermogravimetric analysis and kinetic modeling of low-transition-temperature mixtures pretreated oil palm empty fruit bunch for possible maximum yield of pyrolysis oil

The impacts of low-transition-temperature mixtures (LTTMs) pretreatment on thermal decomposition and kinetics of empty fruit bunch (EFB) were investigated by thermogravimetric analysis. EFB was pretreated with the LTTMs under different duration of pretreatment which enabled various degrees of alteration to their structure. The TG-DTG curves showed that LTTMs pretreatment on EFB shifted the temperature and rate of decomposition to higher values. The EFB pretreated with sucrose and choline chloride-based LTTMs had attained the highest mass loss of volatile matter (78.69% and 75.71%) after 18 h of pretreatment. For monosodium glutamate-based LTTMs, the 24 h pretreated EFB had achieved the maximum mass loss (76.1%). Based on the Coats-Redfern integral method, the LTTMs pretreatment led to an increase in activation energy of the thermal decomposition of EFB from 80.00 to 82.82-94.80 kJ/mol. The activation energy was mainly affected by the demineralization and alteration in cellulose crystallinity after LTTMs pretreatment.

Controlling the cleavage of the inter- and intra-molecular linkages in lignocellulosic biomass for further biorefining: A review

The abundant intermolecular linkages among cellulose, hemicellulose and lignin significantly limit the utilization of the most promising renewable biomass. Process control with solvents, catalysts and temperature is of significant importance providing ways to break the above linkages, and benefiting to the further conversion of the main biomass components to small molecular products. This article discusses the effect of catalyst under hydrothermal and organosolv treatment emphasizing the cleavage of the intermolecular linkage. Acidic catalysts show good performance on cleaving the linkages between carbohydrates and lignin. Basic catalysts promoted the dissolution of lignin component. Hydrogenolysis assisted conversion of lignin can efficiently break the intermolecular linkages to yield lignin-derived bio-oil, especially in co-solvent reaction system. Besides, the effects of single solvent and co-solvent systems, as well as the cleavage of the intramolecular linkages to yield target chemicals are also included. Several further study strategies are proposed.

Coproduction of lignin and glucose from vine shoots by eco-friendly strategies: Toward the development of an integrated biorefinery

The objective of this work was to study the suitability of the pretreated vine shoots as a source of lignin and to determine its structural features. The best conditions to achieve the aim of this work were 12% NaOH, 124°C and 105min, as they permitted a removal of 67.7% of the lignin present in the pretreated vine shoots and the obtaining of a solid with a 69.4% of glucan. This delignified solid was subjected to an enzymatic hydrolysis achieving a conversion of glucan to glucose close to 100%. The characterization of lignins extracted from pretreated vine shoots was carried out for the first time and the following techniques were employed: a quantitative acid hydrolysis, HPSEC, TGA, FTIR and Pyrolysis-GC/MS. With this proposal, products from the main fractions of the vine shoots (hemicellulosic oligosaccharides, lignin fragments and cellulosic substrates) could be obtained separately, being potentially suitable for further applications.

The Phenylpropanoid Pathway and Lignin in Defense against Ganoderma boninense Colonized Root Tissues in Oil Palm (Elaeis guineensis Jacq.)

Basal stem rot, caused by the basidiomycete fungus, Ganoderma boninense, is an economically devastating disease in Malaysia. Our study investigated the changes in lignin content and composition along with activity and expression of the phenylpropanoid pathway enzymes and genes in oil palm root tissues during G. boninense infection. We sampled control (non-inoculated) and infected (inoculated) seedlings at seven time points [1, 2, 3, 4, 8, and 12 weeks post-inoculation (wpi)] in a randomized design. The expression profiles of phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD) genes were monitored at 1, 2, and 3 wpi using real-time quantitative polymerase chain reaction. Seedlings at 4, 8, and 12 wpi were screened for lignin content, lignin composition, enzyme activities (PAL, CAD, and POD), growth (weight and height), and disease severity (DS). Gene expression analysis demonstrated up-regulation of PAL, CAD, and POD genes in the infected seedlings, relative to the control seedlings at 1, 2, and 3 wpi. At 2 and 3 wpi, CAD showed highest transcript levels compared to PAL and POD. DS increased progressively throughout sampling, with 5, 34, and 69% at 4, 8, and 12 wpi, respectively. Fresh weight and height of the infected seedlings were significantly lower compared to the control seedlings at 8 and 12 wpi. Lignin content of the infected seedlings at 4 wpi was significantly higher than the control seedlings, remained elicited with no change at 8 wpi, and then collapsed with a significant reduction at 12 wpi. The nitrobenzene oxidation products of oil palm root lignin yielded both syringyl and guaiacyl monomers. Accumulation of lignin in the infected seedlings was in parallel to increased syringyl monomers, at 4 and 8 wpi. The activities of PAL and CAD enzymes in the infected seedlings at DS = 5-34% were significantly higher than the control seedlings and thereafter collapsed at DS = 69%.