A microwave-assisted aqueous ionic liquid pretreatment to enhance enzymatic hydrolysis of Eucalyptus and its mechanism

Rapid fractionation of corn stover by microwave-assisted protic ionic liquid [TEA][HSO4] for fermentative acetone-butanol-ethanol production

BACKGROUND

The use of ionic liquids (ILs) to fractionate lignocelluloses for various bio-based chemicals productions is in the ascendant. On this basis, the protic ILs consisting of triethylammonium hydrogen sulfate ([TEA][HSO4]) possessed great promise due to the low price, low pollution, and high efficiency. In this study, the microwave-assistant [TEA][HSO4] fractionation process was established for corn stover fractionation, so as to facilitate the monomeric sugars production and supported the downstream acetone-butanol-ethanol (ABE) fermentation.

RESULTS

The assistance of microwave irradiation could obviously shorten the fractionation period of corn stover. Under the optimized condition (190 W for 3 min), high xylan removal (93.17 ± 0.63%) and delignification rate (72.90 ± 0.81%) were realized. The mechanisms for the promotion effect of the microwave to the protic ILs fractionation process were ascribed to the synergistic effect of the IL and microwaves to the depolymerization of lignocellulose through the ionic conduction, which can be clarified by the characterization of the pulps and the isolated lignin specimens. Downstream valorization of the fractionated pulps into ABE productions was also investigated. The [TEA][HSO4] free corn stover hydrolysate was capable of producing 12.58 g L-1 of ABE from overall 38.20 g L-1 of monomeric sugars without detoxification and additional nutrients supplementation.

CONCLUSIONS

The assistance of microwave irradiation could significantly promote the corn stover fractionation by [TEA][HSO4]. Mass balance indicated that 8.1 g of ABE and 16.61 g of technical lignin can be generated from 100 g of raw corn stover based on the novel fractionation strategy.

Efficacy and Functional Mechanisms of a Two-Stage Pretreatment Approach Based on Alkali and Ionic Liquid for Bioconversion of Waste Medium-Density Fiberboard

A novel pretreatment strategy utilizing a combination of NaOH and 1-Butyl-3-methylimidazolium chloride ([Bmim]Cl) was proposed to enhance the enzymatic hydrolysis of abandoned Medium-density fiberboard (MDF). The synergistic effect of NaOH and [Bmim]Cl pretreatment significantly improved the glucose yield, reaching 445.8 mg/g within 72 h, which was 5.04 times higher than that of the untreated samples. The working mechanism was elucidated according to chemical composition, as well as FTIR, 13C NMR, XRD, and SEM analyses. The combined effects of NaOH and [Bmim]Cl led to lignin degradation, hemicellulose removal, the destruction and erosion of crystalline regions, pores, and an irregular microscopic morphology. In addition, by comparing the enzymatic hydrolysis sugar yield and elemental nitrogen content of untreated MDF samples, eucalyptus, and hot mill fibers (HMF), it was demonstrated that the presence of adhesives and additives in waste MDF significantly influences its hydrolysis process. The sugar yield of untreated MDF samples (88.5 mg/g) was compared with those subjected to hydrothermal pretreatment (183.2 mg/g), Ionic liquid (IL) pretreatment (406.1 mg/g), and microwave-assisted ionic liquid pretreatment (MWI) (281.3 mg/g). A long water bath pretreatment can reduce the effect of adhesives and additives on the enzymatic hydrolysis of waste MDF. The sugar yield produced by the combined pretreatment proposed in this study and the removal ability of adhesives and additives highlight the great potential of our pretreatment technology in the recycling of waste fiberboard.

Microwave Encounters Ionic Liquid: Synergistic Mechanism, Synthesis and Emerging Applications

Progress in microwave (MW) energy application technology has stimulated remarkable advances in manufacturing and high-quality applications of ionic liquids (ILs) that are generally used as novel media in chemical engineering. This Review focuses on an emerging technology via the combination of MW energy and the usage of ILs, termed microwave-assisted ionic liquid (MAIL) technology. In comparison to conventional routes that rely on heat transfer through media, the contactless and unique MW heating exploits the electromagnetic wave-ions interactions to deliver energy to IL molecules, accelerating the process of material synthesis, catalytic reactions, and so on. In addition to the inherent advantages of ILs, including outstanding solubility, and well-tuned thermophysical properties, MAIL technology has exhibited great potential in process intensification to meet the requirement of efficient, economic chemical production. Here we start with an introduction to principles of MW heating, highlighting fundamental mechanisms of MW induced process intensification based on ILs. Next, the synergies of MW energy and ILs employed in materials synthesis, as well as their merits, are documented. The emerging applications of MAIL technologies are summarized in the next sections, involving tumor therapy, organic catalysis, separations, and bioconversions. Finally, the current challenges and future opportunities of this emerging technology are discussed.

Investigation of pre-treatment techniques on spent substrate of Pleurotus ostreatus for enhanced biobutanol production using Clostridium acetobutylicum MTCC 11274

Addressing global energy demand, researchers sought eco-friendly biobutanol production from lignocellulosic waste biomass. In the present research work, five different pre-treatment methods viz., Microwave, Ultrasound, Alkali, Acid, and Hybrid, were investigated to explore its biobutanol production potential by utilizing Pleurotus ostreatus spent as substrate. The compositional and physico-chemical changes of the pre-treated Spent Mushroom Substrate (SMS) were assessed using SEM, FTIR, and XRD. Hybrid pre-treatment (Microwave, Alkali, Ultrasound) showed higher delignification when compared to conventional pre-treatment method. Hybrid pre-treated SMS resulted in higher total reducing sugars (521.53 ± 1.84 mg/g) than indigenous SMS (267.89 ± 1.53 mg/g). Fermentation of hybrid pre-treated SMS with Clostridium acetobutylicum MTCC 11274 produced the highest biobutanol concentration (9.84 ± 0.03 g/L) and yielded 0.38 ± 0.02 g/g of biobutanol. This study revealed that hybrid pre-treatment could be a promising solution for enhanced biobutanol production using SMS biomass.

The green novel approach in hydrolysis of pistachio shell into xylose by microwave-assisted high-pressure CO2 /H2 O

BACKGROUND

Pistachio shell is a valuable lignocellulosic biomass because almost 90% of its hemicellulose fraction is xylan, which can be converted into high value-added compounds such as xylooligosaccarides, xylose, xylitol and furfural. The present study represents a green and novel approach to produce xylose from lignocellulosic biomass. Microwave-assisted high-pressure CO2 /H2 O hydrolysis (MW-HPCO2 ) comprising a combination never previously used was performed to produce xylose from pistachio shell.

RESULTS

Response surface methodology with a Box-Behnken design was implemented to optimize microwave-assisted high-pressure CO2 /H2 O hydrolysis (MW-HPCO2 ). The effect of temperature, time and liquid-to-solid ratio was studied in the ranges of 180-210 °C, 10-30 min and 5-30 mL g-1 , respectively. A maximum xylose yield of 61.39% and minimum degradation compounds (5-hydroxymethyl furfural and furfural) of 11.07% were attained under reaction conditions of 190 °C, 30 min and 18 mL g-1 .

CONCLUSION

The results showed that hydrolysis temperature, time and liquid-to-solid ratio had a strong influence on the xylose yield, as well as on the formation of degradation compounds. MW-HPCO2 significantly increased accessibility to cellulose-derived products in the subsequent enzymatic hydrolysis. The results of the present study reveal that MW-HPCO2 can be a promising green technique for the hydrolysis of lignocellulosic biomass. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A New Microwave-Assisted Protocol for Cellulose Extraction from Eucalyptus and Pine Tree Wood Waste

An enormous interest in the development of efficient protocols for cellulose extraction has been demonstrated in the last few years, although usually based on non-sustainable chemical and thermal approaches. In this work, we propose a new and more sustainable method for cellulose extraction from eucalyptus and pine tree wood waste products exclusively performed using microwave-assisted radiation. The methodology includes three main steps: (i) alkaline treatment; (ii) bleaching I, using H2O2; and (iii) bleaching II, an acidic treatment. Samples obtained in each step were characterized by Fourier-transform Infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results were compared with the structural and thermal profile of the starting materials, a commercially available microcrystalline cellulose and with an industrial paper pulp sample. Results confirmed that for both types of wood wastes, cellulose was retained during the extraction procedures and that the removal of hemicellulose and lignin was mainly achieved in the last step, as seen by the FTIR spectra and TGA curves. The developed protocol is innovative, as it constitutes an easy and quick approach for extracting cellulose from eucalyptus and pine tree wood waste. Mild chemical and thermal conditions are used during the three extraction steps (microwave irradiation, aqueous solutions, maximum of 120 °C in a total of 3 h). Moreover, environmentally friendly purification steps are applied based on the use of water and ethanol. This approach offers the possibility of a future scale-up study to potentially apply the developed protocol to the extraction of cellulose on an industrial scale.

Development of lignocellulosic biorefineries for the sustainable production of biofuels: Towards circular bioeconomy

The idea of environment friendly and affordable renewable energy resources has prompted the industry to focus on the set up of biorefineries for sustainable bioeconomy. Lignocellulosic biomass (LCB) is considered as an abundantly available renewable feedstock for the production of biofuels which can potentially reduce the dependence on petrochemical refineries. By utilizing various conversion technologies, an integrated biorefinery platform of LCB can be created, embracing the idea of the 'circular bioeconomy'. The development of effective pretreatment methods and biocatalytic systems by various bioengineering and machine learning approaches could reduce the bioprocessing costs, thereby making biomass-based biorefinery more sustainable. This review summarizes the development and advances in the lignocellulosic biorefineries from the LCB to the final product stage using various different state-of-the-art approaches for the progress of circular bioeconomy. The life cycle assessment which generates knowledge on the environmental impacts related to biofuel production chains is also summarized.

High-pressure microwave-assisted pretreatment of softwood, hardwood and non-wood biomass using different solvents in the production of cellulosic ethanol

BACKGROUND

Pretreatment is an indispensable stage of the preparation of lignocellulosic biomass with key significance for the effectiveness of hydrolysis and the efficiency of the production of cellulosic ethanol. A significant increase in the susceptibility of the raw material to further degradation can be attained as a result of effective delignification in high-pressure conditions. With this in mind, a method of high-pressure pretreatment using microwave radiation and various solvents (water, 40% w/v NaCS, 1% v/v H₂SO₄, 1% w/v NaOH or 60% v/v EtOH with an addition of 1% v/v H₂SO₄) was developed, enabling the acquisition of biomass with an increased susceptibility to the process of enzymatic hydrolysis. The medium obtained in this way can be used for the production of cellulosic ethanol via high-gravity technology (lignocellulosic media containing from 15 to 20% dry weight of biomass). For every type of biomass (pine chips, beech chips and wheat straw), a solvent was selected to be used during the pretreatment, guaranteeing the acquisition of a medium highly susceptible to the process of enzymatic hydrolysis.

RESULTS

The highest efficiency of the hydrolysis of biomass, amounting to 71.14 ± 0.97% (glucose concentration 109.26 ± 3.49 g/L) was achieved for wheat straw subjected to microwave-assisted pretreatment using 40% w/v NaCS. Fermentation of this medium produced ethanol concentration at the level of 53.84 ± 1.25 g/L. A slightly lower effectiveness of enzymatic hydrolysis (62.21 ± 0.62%) was achieved after high-pressure microwave-assisted pretreatment of beech chips using 1% w/v NaOH. The hydrolysate contained glucose in the concentration of 91.78 ± 1.91 g/L, and the acquired concentration of ethanol after fermentation amounted to 49.07 ± 2.06 g/L. In the case of pine chips, the most effective delignification was achieved using 60% v/v EtOH with the addition of 1% v/v H₂SO₄, but after enzymatic hydrolysis, the concentration of glucose in hydrolysate was lower than in the other raw materials and amounted to 39.15 ± 1.62 g/L (the concentration of ethanol after fermentation was ca. 19.67 ± 0.98 g/L). The presence of xylose and galactose was also determined in the obtained fermentation media. The highest initial concentration of these carbohydrates (21.39 ± 1.44 g/L) was observed in beech chips media after microwave-assisted pretreatment using NaOH. The use of wheat straw after pretreatment using EtOH with an addition of 1% v/v H₂SO₄ for the preparation of fermentation medium, results in the generation of the initial concentration of galactose and xylose at the level of 19.03 ± 0.38 g/L.

CONCLUSION

The achieved results indicate a high effectiveness of the enzymatic hydrolysis of the biomass subjected to high-pressure microwave-assisted pretreatment. The final effect depends on the combined use of correctly selected solvents for the different sources of lignocellulosic biomass. On the basis of the achieved results, we can say that the presented method indicates a very high potential in the area of its use for the production of cellulosic ethanol involving high-gravity technology.

Challenges and perspectives of green-like lignocellulose pretreatments selectable for low-cost biofuels and high-value bioproduction

Lignocellulose represents the most abundant carbon-capturing substance that is convertible for biofuels and bioproduction. Although biomass pretreatments have been broadly applied to reduce lignocellulose recalcitrance for enhanced enzymatic saccharification, they mostly require strong conditions with potential secondary waste release. By classifying all major types of pretreatments that have been recently conducted with different sources of lignocellulose substrates, this study sorted out their distinct roles for wall polymer extraction and destruction, leading to the optimal pretreatments evaluated for cost-effective biomass enzymatic saccharification to maximize biofuel production. Notably, all undigestible lignocellulose residues are also aimed for effective conversion into value-added bioproduction. Meanwhile, desired pretreatments were proposed for the generation of highly-valuable nanomaterials such as cellulose nanocrystals, lignin nanoparticles, functional wood, carbon dots, porous and graphitic nanocarbons. Therefore, this article has proposed a novel strategy that integrates cost-effective and green-like pretreatments with desirable lignocellulose substrates for a full lignocellulose utilization with zero-biomass-waste liberation.

An eco-friendly novel approach for bioconversion of Saccharum spontaneum biomass to biofuel-ethanol under consolidated bioprocess

Quest for renewable/eco-friendly energy sources has received immense focus in recent years. Current study involved consolidated bioprocessing of Saccharum spontaneum biomass (SSB) for biofuel-ethanol generation in a 'one pot consolidated bioprocess' (OPCB). SSB was pretreated with protic ionic liquid, triethylamine-bisulfate ([TEA][HSO₄]), saccharified in-situ with cellulase/xylanase enzymes, and the released sugars were fermented to ethanol. Pretreatment and saccharification processes were optimized under OPCB to achieve 2.70-fold increased sugar yield i.e. from 196.56 to 531.00 mg/g biomass. Fermentation of sugars yielded ethanol at 209.6 mg/g biomass at a bioconversion efficiency of 72.56 %. The pretreated SSB was comprehensively examined by/for XRD, NMR, SEM, FT-IR, and properties such as water retention capacity, surface area and cellulase adsorption ability to elucidate functional mechanisms of [TEA][HSO₄] pretreatment.

A Novel Potent Crystalline Chitin Decomposer: Chitin Deacetylase from Acinetobacter schindleri MCDA01

Chitosan is a functional ingredient that is widely used in food chemistry as an emulsifier, flocculant, antioxidant, or preservative. Chitin deacetylases (CDAs) can catalyze the hydrolysis of acetyl groups, making them useful in the clean production of chitosan. However, the high inactivity of crystalline chitin catalyzed by CDAs has been regarded as the technical bottleneck of crystalline chitin deacetylation. Here, we mined the AsCDA gene from the genome of Acinetobacter schindleri MCDA01 and identified a member of the uraD_N-term-dom superfamily, which was a novel chitin deacetylase with the highest deacetylation activity. The AsCDA gene was expressed in Escherichia coli BL21 by IPTG induction, whose activity to colloidal chitin, α-chitin, and β-chitin reached 478.96 U/mg, 397.07 U/mg, and 133.27 U/mg, respectively. In 12 h, the enzymatic hydrolysis of AsCDA removed 63.05% of the acetyl groups from α-chitin to prepare industrial chitosan with a degree of deacetylation higher than 85%. AsCDA, as a potent chitin decomposer in the production of chitosan, plays a positive role in the upgrading of the chitosan industry and the value-added utilization of chitin biological resources.

Effect of microwave/hydrothermal combined ionic liquid pretreatment on straw: Rumen anaerobic fermentation and enzyme hydrolysis

To explore green technology for wheat straw pretreatment, this study combined the microwave or hydrothermal with ionic liquid ([Bmim][OAc]) on wheat straw followed by rumen fermentation. The optimal conditions of microwave assisted ionic liquids pretreatment (M-I) and hydrothermal assisted ionic liquids pretreatment (H-I) treatment were 360 W and 200 °C, and the corresponding lignin removal rates reached 35.3% and 25.4%, respectively. Rumen fermentation showed that the highest volatile fatty acid (VFA) yield was found in M-I group, followed by H-I group at 234 and 180 mg/g, respectively. As for enzymatic hydrolysis, the saccharification rates at 3 days of M-I (360 W) and H-I (200 °C) were determined to be 393 and 320 mg/g. The optimal ionic liquid dosage was determined to be 30% in consideration of cost and VFA conversion rate. M-I pretreatment plus the rumen fermentation enjoyed the benefit of no enzyme addition and high product recovery, which was worth further investigating.

Nanobiocatalysts for efficacious bioconversion of ionic liquid pretreated sugarcane tops biomass to biofuel

This work aimed to study the hydrolysis of ionic liquid (IL) pretreated sugarcane tops (SCT) biomass with in-house developed IL-stable enzyme preparation, from a fungal isolate Aspergillus flavus PN3. Maximum reducing sugar yield (181.18 mg/g biomass) was obtained from tris (2-hydroxyethyl) methylammonium-methylsulfate ([TMA]MeSO₄) pretreated biomass. Pretreatment parameters were optimized to attain enhanced sugar yield (1.57-fold). Functional mechanism of IL mediated pretreatment of SCT biomass was elucidated by SEM, XRD, FTIR and ¹H NMR studies. Furthermore, nanobiocatalysts prepared by immobilization of enzyme preparation by covalent coupling on magnetic nanoparticles functionalized with amino-propyl triethoxysilane, were assessed for their hydrolytic efficacy and reusability. Nanobiocatalysts were examined by SEM and FTIR analysis for substantiation of immobilization. This is the first ever report of application of magnetic nanobiocatalysts for saccharification of IL-pretreated sugarcane tops biomass.

Agricultural bio-waste for removal of organic and inorganic contaminants from waste diesel engine oil

Corncob, an agricultural bio-waste, was used as adsorbent to remove organic and inorganic contaminants in waste lubricating oil (WLO) from diesel engine. To improve its adsorption capacity, corncob was modified with mixed solution of nitric acid, Hexadecyl trimethyl ammonium bromide and ethanol. Characterization results showed the crystallinity index of corncob enhanced 12%, which would be ascribed to the disruption of the dense lignin-carbohydrates structure in lignocellulose biomass by modification. The surface of modified corncob became smoother and porous. The adsorption results showed modified corncob had better removal rates to contaminants than raw corncob. For WLO with 80,000 km mileage, the removal rates to Fe, Al, Cu were enhanced from 19%, 6.4%, 48-27%, 27%, 53%, while that for oxide, sulphate, aromates, soot and insoluble resins were enhanced 1.7, 1.2, 3.0, 1.7 and 1.7 times. The reduction rate of total acid number to WLO with 40,000, 60,000, 80,000 km were enhanced 16%, 9%, 12% by modified corncob, respectively. The optimal adsorption condition was explored as adsorbing 60 min at 90 °C with 2% adsorbent. Corncob, with the advantages of low cost, good biodegradability and high adsorption capacity, could be used as alternative to conventional adsorbent for WLO.

Transforming lignocellulosic biomass into biofuels enabled by ionic liquid pretreatment

Processes that can convert lignocellulosic biomass into biofuels and chemicals are particularly attractive considering renewability and minimal environmental impact. Ionic liquids (ILs) have been used as novel solvents in the process development in that they can effectively deconstruct recalcitrant lignocellulosic biomass for high sugar yield and lignin recovery. From cellulose-dissolving ILs to choline-based and protic acidic ILs, extensive research in this field has been done, driven by the promising future of IL pretreatment. Meanwhile, shortcomings and technological hurdles are ascertained during research and developments. It is necessary to present a general overview of recent developments and challenges in this field. In this review paper, three aspects of advances in IL pretreatment are critically analyzed: biocompatible ILs, protic acidic ILs and combinatory pretreatments.

A Study of the Ionic Liquid-Based Ultrasonic-Assisted Extraction of Isoliquiritigenin from Glycyrrhiza uralensis

We successfully extracted isoliquiritigenin from Glycyrrhiza uralensis through the utilization of an ionic liquid-based ultrasonic-assisted extraction (ILUAE) approach. Briefly, we utilized the solution of 1-butyl-3-methylimidazolium bromide ([BMIM]Br) as solvent and optimized key ILUAE parameters such as solid-liquid ratios, concentrations of ionic liquids, and the times of ultrasonication. Based on a single-factor experiment, we utilized the response surface method (RSM) approach to optimize the extraction procedure. The approach revealed that the optimal energy consumption time was 120 min, with the ultrasonic extraction temperature of 60°C. Using these optimized parameters together with the solid-liquid ratio (dried G. uralensis powder: [BMIM]Br of 0.3 mol/L) of 1 : 16.163 and the [BMIM]Br of 0.3 mol/L, we achieved a 0.665 mg/g extraction yield. Overall, these findings thus indicate that we were able to effectively use ILUAE as an efficient approach to reliably extract isoliquiritigenin in a reproducible and environmentally friendly manner.

Technologies for Eucalyptus wood processing in the scope of biorefineries: A comprehensive review

Eucalyptus is the most widely planted type of hardwoods, and represents an important biomass source for the production of fuels, chemicals, and materials. Its industrial benefit can be achieved by processes following the biorefinery concept, which is based on the selective separation ("fractionation") of the major components (hemicelluloses, cellulose and lignin), and on the generation of added-value from the resulting fractions. This article provides a in-depth assessment on the composition of Eucalyptus wood and a critical evaluation of selected technologies allowing its overall exploitation. These latter include treatments with organosolvents and with emerging fractionation agents (ionic liquids and deep eutectic solvents). The comparative evaluation of the diverse processing technologies is carried out in terms of degree of fractionation, yields and selectivities. The weak and strong points, challenges, and opportunities of the diverse fractionation methods are identified, focusing on the integral utilization of the feedstocks.

Sugar Production from Hybrid Poplar Sawdust: Optimization of Enzymatic Hydrolysis and Wet Explosion Pretreatment

Wet explosion pretreatment of hybrid poplar sawdust (PSD) for the production of fermentable sugar was carried out in the pilot-scale. The effects of pretreatment conditions, such as temperature (170-190 °C), oxygen dosage (0.5-7.5% of dry matter (DM), w/w), residence time (10-30 min), on cellulose and hemicellulose digestibility after enzymatic hydrolysis were ascertained with a central composite design of the experiment. Further, enzymatic hydrolysis was optimized in terms of temperature, pH, and a mixture of CTec2 and HTec2 enzymes (Novozymes). Predictive modeling showed that cellulose and hemicellulose digestibility of 75.1% and 83.1%, respectively, could be achieved with a pretreatment at 177 °C with 7.5% O2 and a retention time of 30 min. An increased cellulose digestibility of 87.1% ± 0.1 could be achieved by pretreating at 190 °C; however, the hemicellulose yield would be significantly reduced. It was evident that more severe conditions were required for maximal cellulose digestibility than that of hemicellulose digestibility and that an optimal sugar yield demanded a set of conditions, which overall resulted in the maximum sugar yield.

Enhancing the Enzymatic Saccharification of Grain Stillage by Combining Microwave-Assisted Hydrothermal Irradiation and Fungal Pretreatment

Grain stillage from the liquor industry was pretreated by using microwave-assisted hydrothermal pretreatment, fungal pretreatments, and their combination to enable efficient enzymatic hydrolysis for sugar production. The microwave-assisted hydrothermal (MH) pretreatment was optimized by using a response surface methodology, and the respective maximum reducing sugar yield and saccharification efficiency of 17.59 g/100 g and 33.85%, respectively, were achieved under the pretreatment conditions of microwave power = 120 W, solid-to-liquid ratio = 1:15 (g·mL^-1), and time = 3.5 min. The fungal pretreatment with Phanerochaete chrysosporium digestion (PC) achieved the maximum ligninolytic enzyme activities in 6 days with 10% inoculum size at which the reducing sugar yield and saccharification efficiency reached 19.74 g/100 g and 36.29%, respectively. To further improve the pretreatment efficiency, MH and PC pretreatments were combined, but the sequence of MH and PC mattered on the saccharification efficiency. The MH + PC pretreatment (the MH prior to the PC) was better than PC + MH (the PC prior to the MH) in terms of saccharification efficiency. Overall, the MH + PC pretreatment achieved superior reducing sugar yield and saccharification efficiency (25.51 g/100 g and 66.28%, respectively) over all other studied pretreatment methods. The variations of chemical compositions and structure features of the raw and pretreated grain stillage were characterized by using scanning electron microscopy and Fourier transform infrared spectroscopy. The results reveal that both MH and PC pretreatments mainly functioned on delignification and decreasing cellulose crystallinity, thus enhancing the enzymatic saccharification of the pretreated grain stillage. The combined MH and PC pretreatment could be a promising method to enable cost-efficient grain stillage utilization for downstream applications such as biofuels.

Comparison of Fenton and bismuth ferrite Fenton-like pretreatments of sugarcane bagasse to enhance enzymatic saccharification

This study compared enzymatic saccharification of sugarcane bagasse (SCB) after application of two different pretreatment methods, Fenton pretreatment (FP) and BiFeO₃ Fenton-like pretreatment (BFP). The composition, morphology and structural properties of SCB with different pretreatments were analyzed. Results showed that, after BFP, the yield of reducing sugar of SCB under enzymatic saccharification for 72 h was 25.8%, and the sugar conversion rate was 36.6%, which were 2.2 and 2.4-fold those of the FP, respectively. Moreover, the removal of hemicellulose and delignification in the BFP was more severe than that in the FP. The determination of hydroxyl radical (OH) in the two different Fenton processes revealed that the OH generated in the BiFeO₃ Fenton-like system was higher in concentration and longer in action time than that in the Fenton system, which was likely key to the stronger effect of BFP than FP on the enzymatic saccharification of SCB.

Zirconium based metal-organic framework in-situ assisted hydrothermal pretreatment and enzymatic hydrolysis of Platanus X acerifolia exfoliating bark for bioethanol production

Metal-organic framework (MOF) assisted hydrothermal pretreatment and co-catalysis strategy based on UiO-66 MOF is developed for the first time. The Planetree exfoliating bark was pretreated with or without UiO-66 assisted hydrothermal method at a temperature ranging from 160 to 240 °C for 1-3 h residence. With the rise of pretreatment severity, the total reducing sugar (TRS) was increased till reached maximum, 180 mg g^-1, in the presence of UiO-66. The fitting models validate the optimal hydrothermal condition was at 180 °C and 1 h, which was characterized with high TRS and very low yield of furfural and HMF. The TRS from enzymatic hydrolysis reaches maximum, 391 mg g^-1, in the presence of MOF co-catalysis and the maximum ethanol yield achieved was 73%. Altered morphology, higher surface area and porosity are noticed after MOF assisted hydrothermal pretreatment. This study insights the MOFs' application in lignocellulose biomass processing.

New Developments in Material Preparation Using a Combination of Ionic Liquids and Microwave Irradiation

During recent years, synthetic methods combining microwaves and ionic liquids became accepted as a promising methodology for various materials preparations because of their high efficiency and low energy consumption. Ionic liquids with high polarity are heated rapidly, volumetrically and simultaneously under microwave irradiation. Hence, combination of microwave irradiation as a heating source with ionic liquids with various roles (e.g., solvent, additive, template or reactant) opened a completely new technique in the last twenty years for nanomaterials and polymers preparation for applications in various materials science fields including polymer science. This review summarizes recent developments of some common materials syntheses using microwave-assisted ionic liquid method with a focus on inorganic nanomaterials, polymers, carbon-derived composites and biomass-based composites. After that, the mechanisms involved in microwave-assisted ionic-liquid (MAIL) are discussed briefly. This review also highlights the role of ionic liquids in the reaction and crucial issues that should be addressed in future research involving this synthesis technique.