Combination of Superheated Steam with Laccase Pretreatment Together with Size Reduction to Enhance Enzymatic Hydrolysis of Oil Palm Biomass.

The combination of superheated steam (SHS) with ligninolytic enzyme laccase pretreatment together with size reduction was conducted in order to enhance the enzymatic hydrolysis of oil palm biomass into glucose. The oil palm empty fruit bunch (OPEFB) and oil palm mesocarp fiber (OPMF) were pretreated with SHS and ground using a hammer mill to sizes of 2, 1, 0.5 and 0.25 mm before pretreatment using laccase to remove lignin. This study showed that reduction of size from raw to 0.25 mm plays important role in lignin degradation by laccase that removed 38.7% and 39.6% of the lignin from OPEFB and OPMF, respectively. The subsequent saccharification process of these pretreated OPEFB and OPMF generates glucose yields of 71.5% and 63.0%, which represent a 4.6 and 4.8-fold increase, respectively, as compared to untreated samples. This study showed that the combination of SHS with laccase pretreatment together with size reduction could enhance the glucose yield.

Lignin-Degrading Abilities of Novel Autochthonous FungalIsolates Trametes hirsuta F13 and Stereum gausapatum F28.

The aim of this research is to isolate and identify fungi with high lignin-degrading abilities that are autochthonous to southern Serbian region. Two novel fungal isolates identified as Trametes hirsuta F13 and Stereum gausapatum F28 were selected to assess their ligninolytic enzyme activities and the efficiency of lignin removal from beech wood sawdust. Obtained results show that both isolates are good sources of industrially valuable enzymes with a potential for application in various biotechnological and industrial processes. Both isolates showed laccase, manganese-dependent peroxidase, and versatile peroxidase activities, while only S. gausapatum F28 had lignin peroxidase activity. This is the first record of the ability of S. gausapatum species to produce lignin peroxidase. T. hirsuta F13 showed higher laccase activity than S. gausapatum F28, while S. gausapatum F28 had higher manganese peroxidase activity. Also, T. hirsuta F13 exhibited much higher laccase activity under submerged cultivation conditions than solid-state cultivation conditions, which is rare for fungi. This is important for industrial processes since the submerged fermentation is a dominant technique in industry. The test of the efficiency of lignin removal showed that both isolates are efficient lignin decomposers. After five weeks of incubation on beech wood sawdust, the total lignin losses were 33.84% with T. hirsuta F13 and 28.8% with S. gausapatum F28.

Novel supramolecular deep eutectic solvent-enabled in-situ lignin protection for full valorization of all components of wheat straw.

Lignin is usually deemed as an inhibitor to enzymatic hydrolysis of cellulose due to its physical barrier, non-productive adsorption, and steric hindrance. Herein, a novel supramolecular deep eutectic solvent (SUPRADES), comprising ethylene glycol and citric acid in 5:1 M ratio, and ß-cyclodextrin (ß-CD) in a concentration of 3.5% (w/w), was developed to be efficient for pretreating wheat straw. The delignification rate, cellulose enzymatic digestibility, and hemicellulose removal reached 90.45%, 97.36% and 87.24%, respectively, which may be attributed to the introduction of ß-CD with superior ability of both adsorption and in-situ lignin protection to efficiently remove lignin with intact structure from cellulose surface. The mechanisms of high-efficiency lignin extraction/protection were systematically illustrated by adsorption kinetics. Moreover, Trichosporon cutaneum grown on the hemicellulose and cellulose fractions after pretreatment afforded 8.8 g total lipids from 100 g wheat straw. The green SUPARDES pretreatment strategy offers a new avenue for upgrading lignocellulose to biofuels.

A novel mineral-acid free biphasic deep eutectic solvent/γ-valerolactone system for furfural production and boosting the enzymatic hydrolysis of lignocellulosic biomass.

The failure of hemicellulose valorization in a deep eutectic solvent (DES) pretreatment has become a bottleneck that challenges its further development. To address this issue, this study developed a DES/GVL (γ-valerolactone) biphasic system for effective hemicellulose-furfural conversion, enhanced cellulose saccharification and lignin isolation. The results indicated that the biphasic system could significantly improve the lignin removal (as high as 89.1%), 86.0% higher than the monophasic DES, accompanied by âˆ¼100% hemicellulose degradation. Notably, the GVL in the biphasic solvent restricted the condensation of hemicellulose degradation products, which as a result generated large amount of furfural in the pretreatment liquid with a yield of 68.6%. With the removal of hemicellulose and lignin, cellulose enzymatic hydrolysis yield was boosted and reached near 100%. This study highlighted that the novel DES/GVL is capable of fractionating the biomass and benefiting their individual utilization, which could provide a new biorefinery configuration for a DES pretreatment.

Oxidation-driven lignin removal by Agaricus bisporus from wheat straw-based compost at industrial scale.

Fungi are main lignin degraders and the edible white button mushroom, Agaricus bisporus, inhabits lignocellulose-rich environments. Previous research hinted at delignification when A. bisporus colonized pre-composted wheat straw-based substrate in an industrial setting, assumed to aid subsequent release of monosaccharides from (hemi-)cellulose to form fruiting bodies. Yet, structural changes and specific quantification of lignin throughout A. bisporus mycelial growth remain largely unresolved. To elucidate A. bisporus routes of delignification, at six timepoints throughout mycelial growth (15 days), substrate was collected, fractionated, and analyzed by quantitative pyrolysis-GC-MS, 2D-HSQC NMR, and SEC. Lignin decrease was highest between day 6 and day 10 and reached in total 42 % (w/w). The substantial delignification was accompanied by extensive structural changes of residual lignin, including increased syringyl to guaiacyl (S/G) ratios, accumulated oxidized moieties, and depleted intact interunit linkages. Hydroxypropiovanillone and hydroxypropiosyringone (HPV/S) subunits accumulated, which are indicative for ß-|O-4' ether cleavage and imply a laccase-driven ligninolysis. We provide compelling evidence that A. bisporus is capable of extensive lignin removal, have obtained insights into mechanisms at play and susceptibilities of various substructures, thus we were contributing to understanding fungal lignin conversion.

Chemical oxygen demand and tannin/lignin removal from paper mill wastewater by electrocoagulation combined with peroxide and hypochlorite treatments.

The present investigation sought to assess the practicality of utilizing a combined pre-treatment approach comprising electrocoagulation, peroxide, and hypochlorite treatments for the removal of chemical oxygen demand (COD) and tannin/lignin from paper mill wastewater. The study aimed to optimize the operating parameters with a view to maximizing the removal efficiencies while minimizing energy consumption. A pair of iron electrodes were used as anode and cathode in the study, and the main operating parameters were determined as initial pH, applied current, treatment time and oxidant dosage/COD ratio. Response surface methodology (RSM) was used to evaluate the effect of these parameters on COD and tannin/lignin removals. The primary findings of the investigation indicated that the integration of electrocoagulation with peroxide and hypochlorite treatments exhibited efficacy in removing COD, tannin/lignin, colour, phenol, and turbidity from paper mill wastewater. The optimized conditions resulted in COD removal efficiencies of 48.13 ± 2.2% and 29.53 ± 1.4% for EC with H2O2 and Ca(OCl)2, respectively. Tannin/lignin removal efficiencies were 92.59 ± 3.6% and 94.09 ± 1.8% for EC-H2O2 and EC-Ca(OCl)2, respectively. The specific energy consumption (SEC) values showed that EC-Ca(OCl)2 required 7 times more energy than EC-H2O2 for removing 1 kg COD. The principal deduction drawn from the study was that EC-H2O2 pre-treatment demonstrated superior COD removal efficiency and lower energy consumption, while EC-Ca(OCl)2 pre-treatment exhibited greater efficiency in removing toxic and recalcitrant pollutants. In future studies, it would be useful to conduct research to increase COD removal efficiency in addition to tannin/lignin removal in EC-Ca(OCl)2 process.

Optimization of softwood pretreatment by microwave-assisted deep eutectic solvents at high solids loading.

Microwave-assisted deep eutectic solvent (DES) has received attention as an ultrafast pretreatment method in lignocellulose fractionation. This study investigated the improvement of milled softwood mixture (MSM) fractionation with chlorine chloride-formic acid (ChCl:FA) to obtain residues with high glucan retention and purity while removing majority of the lignin and hemicelluloses. At the optimum pretreatment conditions i.e., ChCl:FA (1:4), 140 °C, 14 min, 800 W and 15 % (w/v), 96.2 % hemicellulose removal, 90.1 % delignification and 93.5 % glucan retention were achieved. About 85 % lignin was recovered with a 95 % purity when solid loading was 10-20 % (w/v). This study showed that microwave assisted ChCl:FA pretreatment was a suitable means to fractionate MSM to achieve high quality glucan and lignin at high solid loading.

Adsorption properties of active biochar: Overlooked role of the structure of biomass.

Vascular plants account for more than 80% of all biomass on earth and are potential precursors of biochar. However, the changes of vascular bundle have received less attention during the preparation of biochar. In this study, loofah sponge (LS), tangerine pith (TP), and rhodiola rosea (RR), were selected to show the role of vascular bundle in biochar through the pretreatment of vascular bundle. The results showed that the active biochar prepared with vascular bundle protection had high adsorption capacity for methylene blue (LS: 953.53 mg/g, TP: 714.77 mg/g, RR: 583.49 mg/g). The Brunauer-Emmett-Teller method was used to measure the specific surface area (SSA) of active biochar. The SSA of LS active biochar prepared by vascular bundle protection was 2262.67 m2/g, and has high adsorption properties under different conditions. In conclusion, the protection of vascular bundle during biochar preparation is important to improve the utilization of biological resources and environmental adsorption.

Lignin removal, reducing sugar yield and photo-fermentative biohydrogen production capability of corn stover: Effects of different pretreatments.

The effects of different pretreatment methods, including hydrothermal, acid, alkali, acid-heat and alkali-heat on lignin removal, reducing sugar (RS) yield and photo-fermentative biohydrogen production (PFHP) capability of corn stover (CS) were studied. NaOH-heat pretreatment was the most effective for lignin removal from CS, and the lignin removal rate reached 77%. All the studied pretreatment methods improved the total RS yield of CS, and the highest total RS yield (46.1 g/100 g raw material (RM)) was obtained from 2% NaOH-heat pretreated CS. 2% NaOH pretreatment realized the best PFHP of CS, which increased the hydrogen yield (HY), maximal hydrogen production rate (HPR) and highest hydrogen content (HC) by 31.9%, 50.9% and 20.1% respectively, and shortened hydrogen production lag time (HPLT) by 58.8% over that of untreated CS. However, NaOH-heat and 4% NaOH pretreatment weakened the PFHP capability of CS.

Rice straw pretreatment using cow breeding wastewater for methane production.

The aim of this study was to investigate the pretreatment of rice straw using cow breeding wastewater. The effects of filtering cow breeding wastewater through rice straw and microaerobic treatment on the pretreatment characteristics and methane production of rice straw were investigated. Generally, the filtration improved the pretreatment effect by adsorbing ammonium nitrogen and achieved higher solids loading for pretreatment. Although airtight treatment was optimal, the lignin removal and methane production of semi-sealed rice straw were only slightly lower than those of sealed rice straw. However, the results of open treatment were similar to those of the control. The maximum lignin removal and methane production reached 68.08% and 292.62 L/kg volatile solids (VS), respectively, for the filtered rice straw soaked in cow breeding wastewater again during pretreatment, and 61.26% and 274.18 L/kg VS, respectively, for the filtered rice straw pretreated directly without soaking.

Brief Dataset on produced handsheet from oil palm residue lignocellulose treated with Bacillus cereus on mechanical and physical characterization.

This article presents experimental data on oil palm biomass (oil palm leaves, oil palm trunk and empty fruit bunch) handsheet production characterization by biodelignification treatment using Bacillus cereus extracted from termite gut (Coptotermus curvignathus). It associates the lignocellulose chemical composition obtained via technical association pulp and paper industry TAPPI T 222 om-02 testing on lignin content reduction determination, holocellulose and hemicellulose content determination (Kurscher-Hoffner method). Several data obtained for handsheet characterization presents brightness, opacity, contrast ratio, din transparency, thickness, bursting and tearing indexes are collected. Handsheet surface morphology was also observed on ratio of gaps differences between fiber bonding conducted using scanning electron microscope (SEM) and ImageJ software. The raw data findings supplement chemical composition analysis for both untreated and treated substrates on handsheet quality performance check as presented in the research article "Bio-Mechanical Pulping of Bacteria Pre-Treatment on Oil Palm Biomass for Handsheet Production" [1]. For understanding correlations into the difference among lignocellulose content composition which affect the handsheet formation and mechanical strength refer to article from this research [1]. This dataset is made publicly available for optimizing alternative waste material reuse in the pulp and paper industrial section.

Conversion of rice husk into fermentable sugar and silica using acid-catalyzed ionic liquid pretreatment.

Rice husk is a bulky byproduct with a high silica content from rice milling. In this study, the application of an acid-catalyzed ionic liquid (IL) pretreatment was studied for processing rice husks with a rugged structure. The pretreatment conditions were 130°C for 30 min with 1.2 wt% HCl. The results of enzymatic hydrolysis demonstrated that cellulose conversion of HCl-BMIMCl-treated at 48 h was increased by 660.05%, 538.81%, and 376.55% compared with the untreated, HCl-treated, and BMIMCl-treated rice husks, respectively. Composition analysis demonstrated that most of the hemicellulose was removed in the acid-IL combined treatment. Moreover, scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared analyses indicated that the crystalline structure and outer silica layer of the rice husks were efficiently broken up. The results revealed that the HCl-catalyzed dissolution is highly favorable for the industrial application of rick husks in the production of fermentable sugar and high-purity silica.

Integrating chemical and biological catalysis for simultaneous production of polyphenolics and butyric acid from waste pomegranate peels.

Pomegranate peels are an abundant agricultural waste material with a high content of carbohydrates and bioactive compounds. The aim of this study was to efficiently convert waste pomegranate peels (WPP) into high-value-added products. First, high yields of phenolics (12.2%) and bioactive pectin (24.8%) were obtained via enzymatic pretreatment. The lignin was subsequently degraded using an integrated method combining heteropolyacids as catalyst and biomass-derived γ-valerolactone as sustainable solvent and cellulase-catalyzed hydrolysis. The optimal degradation conditions were found to encompass a temperature of 293 K, reaction time of 3 h and catalyst loading with 30 mM heteropolyacids. Under these conditions, the enzymatic hydrolysis efficiency was enhanced significantly, leading to a yield of 93.3% glucose from the obtained cellulosic feedstock. Finally, the fermentable sugars together with the previously recovered pectin from WPP were firstly used as carbon source to evaluate their suitability as feedstock for butyric acid production using Clostridium tyrobutyricum.

Synergism of sweeping frequency ultrasound and deep eutectic solvents pretreatment for fractionation of sugarcane bagasse and enhancing enzymatic hydrolysis.

Sugarcane bagasse (SCB) is an abundant agricultural waste in China and the conversion of the waste into plethora of useful resources is very vital. To achieve this, fractionation of the waste is highly important in the biomass biorefinery. The present study aims at investigating the synergistic role of deep eutectic solvents (DES) with sweeping frequency ultrasound (SFUS) and fixed frequency ultrasound (FFUS) in the fractionation of SCB to enhance the enzymatic saccharification process. Therefore, the effects of ultrasound (US) and DES conditions on the pretreatment efficiency were investigated. Under optimum SCB pretreatment conditions, FFUS (40 kHz, 60 min) + DES (choline chloride (ChCl)-lactic acid (LA), 120 °C, 3 h) and SFUS (40 kHz, 60 min) + DES (ChCl-LA, 120 °C, 3 h), the lignin removal rates were 80.13 and 85.62%, respectively. The hemicellulose removal rates were 78.08 and 90.46%, respectively; and the contents of glucose, xylose and arabinose in the liquid fractions after FFUS + DES pretreatment were 7.07, 17.95 and 3.01%, respectively. However, the yield of glucose, xylose, and cellobiose after enzymatic hydrolysis of the SFUS + DES pretreated SCB were 86.76, 38.68, and 20.76%. Analytical studies revealed that the SFUS + DES pretreatment can effectively destroy the ultrastructure of SCB and reduce the crystallinity of cellulose. Furthermore, the mechanism of pretreatment with SFUS + DES was proposed, which confirmed the excellent performance of SFUS + DES. Thus, the application of SFUS + DES pretreatment was able to improve the removal of lignin and hemicellulose from SCBs.

The key role of delignification in overcoming the inherent recalcitrance of Chinese fir for biorefining.

The enzymatic digestibility of softwood is hindered for its highly recalcitrant nature to enzymatic attack. In this study, the effects of dilute sulfuric acid pretreatment (DSAP), acidic sodium chlorite pretreatment (SCP), and their combined pretreatments (DSA-SCP and SC-DSAP) on Chinese fir sawdust were investigated, respectively. Results demonstrated that lignin was the most important obstacle, and digestibility increased linearly with lignin removal yield. Furthermore, the results revealed that the order of sequential pretreatment significantly affected the delignification, and hemicellulose should be removed first. Compared to SC-DSAP, DSA-SCP involving the hemicellulose-removal-first strategy exhibited higher delignification efficiency. DSA-SCP caused lignin removal of 92.3% and the enzymatic hydrolysis was high of 97.9%. Finally, a regression model with high reliability was established to quickly evaluate pretreatment process. In summary, this study highlighted the importance of delignification for saccharification of softwood and unveiled the effect of hemicellulose on delignification.

Direct observation of endoglucanase fibrillation and rapid thickness identification of cellulose nanoplatelets using constructive interference.

Better understanding through direct observation of the mechanisms involved in chemical and enzymatic hydrolysis of biomass is of great importance, to implement a substitute for the common cellulose standards. We report the hydrolysis of biomass, using exclusively the parenchyma, to isolate cellulose nanoplatelets using a less harsh pretreatment. Then, we show direct evidence of the effect of endoglucanase on the structure of cellulose nanoplatelets, finding that amorphous cellulose is exclusively digested, loosening the cellulose nanofibrils in the process. The analysis of micrographs demonstrates that when cellulose nanoplatelets are deposited on a silicon wafer, its thickness can be qualitatively measured by the interference color detected using an optical microscope. This finding facilitates further studies of mechanisms involved in lignin removal and cellulose nanofibrils production by specific enzymatic digestion.

Enhanced methane production from anaerobic digestion of hybrid Pennisetum by selectively removing lignin with sodium chlorite.

To enhance the biodegradability and methane production of hybrid Pennisetum, a pretreatment method with high selectivity for lignin removal, namely sodium chlorite/acetic acid (SCA) pretreatment, was examined in this work. Results showed that SCA pretreatment can selectively remove lignin with minimal impact on cellulose and hemicellulose. After up to 200 min of SCA treatment, 79.4% of lignin was removed and over 90% of the holocellulose was retained. The physicochemical changes after pretreatment were analyzed by confocal laser scanning microscopy, X-ray diffractometer and Fourier transform infrared spectroscopy, showing that the majority of lignin was removed from secondary cell walls and cell middle lamella while the chlorite-resistant lignin remained in the cell corner. Lignin removal significantly enhanced the biodegradability from 59.6% to 86.4% and increased methane production by 38.3%. Energy balance showed that SCA pretreatment was efficient to increase the energy output of hybrid Pennisetum.

Transparent Wood Composites Fabricated by Impregnation of Epoxy Resin and W-Doped VO2 Nanoparticles for Application in Energy-Saving Windows.

Two types of transparent wood composites with anisotropic structure for energy-saving windows were successfully fabricated by infiltration of epoxy resin dispersion containing tungsten-doped vanadium dioxide nanoparticles (W-doped VO2 NPs) into the delignified wood template and subsequent polymerization. The well integration of the epoxy resin, W-doped VO2 NPs, and the pore-structured wood endowed the anisotropic composites with high visible transmittance (68.2% for the composite prepared from longitudinally cut trees (L-composite), 73.3% for the composite prepared from radically cut trees (R-composite)), obviously different mechanical performance (fracture stress of 74.57 MPa (L-composite) and 56.14 MPa (R-composite) and modulus of 1.47 GPa (L-composite) and 1.23 GPa (R-composite)), and low thermal conductivity (0.20 W·m-1 K-1 (L-composite) and 0.32 W·m-1 K-1 (R-composite)). Moreover, these two kinds of W/VO2 transparent wood composites both show an outstanding thermoregulation ability when they are used as windows. A significant amount of heat (from a simulated light source) was reflected by VO2 NPs, and as a result, the indoor temperature of a demo system had a significant slower temperature increase rate when compared with that for a similar system with a common glass panel applied. Novel transparent wood composites combining a low thermal conductivity wood template and thermochromic VO2 NPs provide a potential solution for replacement of heavy, high thermal conductivity, and infrared transparent glass but still meet indoor occupancy view perception.

Production of xylooligosaccharides and monosaccharides from poplar by a two-step acetic acid and peroxide/acetic acid pretreatment.

BACKGROUND: Populus (poplar) tree species including hybrid varieties are considered as promising biomass feedstock for biofuels and biochemicals production due to their fast growing, short vegetative cycle, and widely distribution. In this work, poplar was pretreated with acetic acid (AC) to produce xylooligosaccharides (XOS), and hydrogen peroxide-acetic acid (HPAC) was used to remove residual lignin in AC-pretreated poplar for enzymatic hydrolysis. The aim of this work is to produce XOS and monosaccharides from poplar by a two-step pretreatment method. RESULTS: The optimal conditions for the AC pretreatment were 170 °C, 5% AC, and 30 min, giving a XOS yield of 55.8%. The optimal HPAC pretreatment conditions were 60 °C, 2 h, and 80% HPAC, resulting in 92.7% delignification and 87.8% cellulose retention in the AC-pretreated poplar. The two step-treated poplar presented 86.6% glucose yield and 89.0% xylose yield by enzymatic hydrolysis with a cellulases loading of 7.2 m/g dry mass. Very high glucose (93.8%) and xylose (94.6%) yields were obtained with 14.3 mg cellulases/g dry mass. Both Tween 80 and ß-glucosidase enhanced glucose yield of HPAC-pretreated poplar by alleviating the accumulation of cellobiose. Under the optimal conditions, 6.9 g XOS, 40.3 g glucose, and 8.9 g xylose were produced from 100 g poplar. CONCLUSIONS: The AC and HPAC pretreatment of poplar represented an efficient strategy to produce XOS and fermentable sugars with high yields. This two-step pretreatment was a recyclable benign and advantageous scheme for biorefinery of the poplar into XOS and monosaccharides.

Importance of lignin removal in enhancing biomass hydrolysis in hot-compressed water.

Beech wood was pretreated by ethanol/water mixture or sodium chlorite/acetic acid mixture to prepare two representative samples rich in cellulose/lignin and cellulose/hemicellulose, respectively. These samples were then hydrolysed in hot-compressed water (HCW) using a semi-continuous reactor under optimal conditions where the secondary reactions in the liquid products were minimised. The glucose recovery in the primary liquid products from hydrolysis in HCW is enhanced to ∼80% for the cellulose/hemicellulose rich sample from ∼56% for the raw sample, while that for the cellulose/lignin rich sample only increases slightly to ∼64%. Despite its highest crystallinity index, the cellulose/hemicellulose rich sample achieves the highest glucose recovery at the shortest reaction time during hydrolysis in comparison with the raw and cellulose/lignin rich samples, clearly demonstrating the importance of lignin removal in enhancing hydrolysis reaction rate and sugar recovery during biomass hydrolysis in HCW.