IL Pretreatment Research Articles

Preparation of Cellulose Nanocrystals by Synergistic Action of Ionic Liquid and Recyclable Solid Acid under Mild Conditions

Cellulose nanocrystals (CNCs) are nanoscale particles made from cellulose. They have many unique properties such as being lightweight, stiff, and renewable, making them promising for a variety of applications in a wide range of industries, including materials science, energy storage, and biomedicine. In this paper, a two-stage (swelling-SA-catalyzed) method including IL pretreatment and solid acid hydrolysis process was developed to extract CNCs with high purity and good thermal stability from microcrystalline cellulose (MCC). In the first stage, the swelling of MCC in ionic liquid was studied with the assistance of ultrasonication, and it was found that the amorphous regions became more disordered while the crystalline areas were selectively retained under the conditions of 30 min of reaction time, 45 °C of temperature, 2% of ionic liquid water content and 1:4 mass ratio of cellulose to ionic liquid. CNCs were extracted using solid acid hydrolysis, with a 45 wt% solid acid to cellulose ratio and a 5.0 h hydrolysis process at 45 °C. The morphology, crystallinity, surface characteristics and thermo stability of the sample were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Results demonstrated the highly thermostable CNCs were successful extracted with rodlike shape of 300 ± 100 nm in length and 20 ± 10 nm in width. Solid acid recovery and reuse were also studied, revealing a promising candidate that can reduce the environmental impact associated with chemical products.

Optimization of OPEFB lignocellulose transformation process through ionic liquid [TEA][HSO4] based pretreatment

Research on the transformation of Oil Palm Empty Fruit Bunches (OPEFB) through pretreatment process using ionic liquid triethylammonium hydrogen sulphate (IL [TEA][HSO4]) was completed. The stages of the transformation process carried out were the synthesis of IL with the one-spot method, optimization of IL composition and pretreatment temperature, and IL recovery. The success of the IL synthesis stage was analyzed by FTIR, H-NMR and TGA. Based on the results obtained, it showed that IL [TEA][HSO4] was successfully synthesized. This was indicated by the presence of IR absorption at 1/λ = 2814.97 cm−1, 1401.07 cm−1, 1233.30 cm−1 and 847.92 cm−1 which were functional groups for NH, CH3, CN and SO2, respectively. These results were supported by H-NMR data at δ (ppm) = 1.217–1.236 (N–CH2–CH3), 3.005–3.023 (–H), 3.427–3.445 (N–H+) and 3.867 (N+H3). The TGA results showed that the melting point and decomposition temperature of the IL were 49 °C and 274.3 °C, respectively. Based on pretreatment optimization, it showed that the best IL composition for cellulose production was 85 wt%. Meanwhile, temperature optimization showed that the best temperature was 120 °C. In these two optimum conditions, the cellulose content was obtained at 45.84 wt%. Testing of IL [TEA][HSO4] recovery performance for reuse has shown promising results. During the pretreatment process, IL [TEA][HSO4] recovery effectively increased the cellulose content of OPEFB to 29.13 wt% and decreased the lignin content to 32.57%. The success of the recovery process is indicated by the increasing density properties of IL [TEA][HSO4]. This increase occurs when using a temperature of 80–100 °C. The overall conditions obtained from this work suggest that IL [TEA][HSO4] was effective during the transformation process of OPEFB into cellulose. This shows the potential of IL [TEA][HSO4] in the future in the renewable energy sector.

Chemo-enzymatic approaches for consolidated bioconversion of Saccharum spontaneum biomass to ethanol-biofuel

A novel strategy involving sodium dodecylsulfate (SDS) (SDS assisted tris (2-hydroxyethyl) methyl- ammonium methyl sulphate ([TMA][MeSO4], ionic liquid) pretreatment of Saccharum spontaneum biomass (SSB) following its enzymatic saccharification, and conversion into ethanol-biofuel in a consolidated bioprocess (CBP) was developed. Ionic liquid stable enzyme preparation developed from Bacillus subtilis G2 was used for saccharification. Optimized pretreatment and saccharification variables enhanced the sugar yield (2.35-fold), which was fermented to ethanol content of 104.42 mg/g biomass with an efficiency of 35.73%. The pretreated biomass was examined for textural/ultrastructural alterations by scanning electron microscopy (SEM), 1H/13C nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), surface area measurements, water retention value, and cellulase adsorption isotherms. The combined [TMA][MeSO4] and SDS pretreatment disrupted the lignocellulosic microfibrils, and increased the porosity and surface area. The study provides new mechanistic insights on combined IL and surfactant pretreatment of biomass for its efficient conversion to biofuel.

Surfactant‐assisted and ionic liquid aqueous system pretreatment for biocatalysis of resveratrol from grape seed residue using an immobilized microbial consortia

An efficient method based on a surfactant (Triton X-100)-assisted and ionic liquid ([C4MIM]Br) aqueous system pretreatment of grape seed residue using immobilized microbial consortia was developed for the simultaneous biocatalysis and extraction of resveratrol. To obtain a high biocatalytic rate, the pretreatment parameters were optimized, and the yield of resveratrol reached 305.98 ± 0.23 μg/g, which was 6.36-fold to that of untreated sample. The optimized IL pretreatment conditions were: immobilized microbial consortia comprising Yeast CICC 1912, Aspergillus oryzae 3.951, and Aspergillus niger 3.3148, concentration of IL 0.75 M, temperature 31°C, time 5 min, and pH 6.5. The optimal surfactant-assisted pretreatment conditions were: concentration of surfactant 3%, pH 6.0, time 25 min, and wet weight of microbial consortia beads 10 g/g. The proposed method was successfully employed to generate a higher biocatalytic yield as well as excellent environmental protection than the conventional solvents used in the biocatalysis of resveratrol. Practical applications Grape seed (Vitis amurensis Rupr.) waste residue from the winemaking process, contains approximately 60%–70% of total extractible grape phenolic compounds. Resveratrol, a phenolic compound belonging to the stilbenes subclass, is mainly produced by grape seed, and it possesses a well-documented bioactivity. However, the supply of resveratrol is limited due to its high production cost. An efficient method of surfactant-assisted and ionic liquid aqueous system pretreatment for the biocatalysis of resveratrol from grape seed residue using immobilized microbial consortia was applied. The results indicate that the developed method exhibits the potential for large-scale catalysis and extraction of bioactive components from plant residue.

Combined pretreatment of sugarcane bagasse using alkali and ionic liquid to increase hemicellulose content and xylanase production

BackgroundLignin in sugarcane bagasse (SB) hinders its utilization by microorganism, therefore, pretreatment methods are employed to make fermentable components accessible to the microbes. Multivariate analysis of different chemical pretreatment methods can aid to select the most appropriate strategy to valorize a particular biomass.ResultsAmongst methods tested, the pretreatment by using sodium hydroxide in combination with methyltrioctylammonium chloride, an ionic liquid, (NaOH+IL) was the most significant for xylanase production by Bacillus aestuarii UE25. Investigation of optimal levels of five significant variables by adopting Box-Behnken design (BBD) predicted 20 IU mL− 1 of xylanase and experimentally, a titer of 17.77 IU mL− 1 was obtained which indicated the validity of the model. The production kinetics showed that volumetric productivity of xylanase was much higher after 24 h (833.33 IU L− 1 h− 1) than after 48 h (567.08 IU L− 1 h− 1). The extracted xylan from SB induced more xylanase in the fermentation medium than pretreated SB or commercially purified xylan. Nuclear Magnetic Resonance, Fourier transform infrared spectroscopy and scanning electron microscopy of SB indicated removal of lignin and changes in the structure of SB after NaOH+IL pretreatment and fermentation.ConclusionCombined pretreatment of SB with alkali and methyltrioctylammonium chloride appeared better than other chemical methods for bacterial xylanase production and for the extraction of xylan form SB.

Efficient bioconversion of sugarcane tops biomass into biofuel-ethanol using an optimized alkali-ionic liquid pretreatment approach

Sugarcane tops (SCT) may be an imperative lignocellulosic feedstock for production of renewable energy in view of ever-rising global energy demands. The current study presents the first ever report of combinative pretreatment of sugarcane tops biomass using ionic liquid (1-ethyl-3-methylimidazolium chloride) and alkali (ammonium carbonate) for effective and enhanced saccharification. The enzymatic hydrolysis of combinatorially pretreated SCT biomass resulted in a significantly higher reducing sugar yield (172.34 mg/g biomass) as compared to that obtained after standalone IL (85.9 mg/g biomass) or alkali pretreatment (102.6 mg/g biomass). The saccharification enzymes (cellulase/xylanase) used for hydrolysis of pretreated SCT biomass were in-house produced from an IL-tolerant, newly isolated fungus Penicillium chrysogenum VS4. Optimization of process variables for combined pretreatment was accomplished based on design of experiments, and enhanced reducing sugar yield was obtained. The experimental design for ascertaining optimal level of process variables, i.e., biomass loading (5.33%, w/w), temperature (100 °C), and time (4.50 h) was validated. Optimization of the process parameters resulted in 25.27% increased reducing sugar yield (215.89 mg/g biomass) as compared to that under unoptimized process. Ultrastructural analysis of SCT biomass after combined pretreatment was investigated by scanning electron microscopy and Fourier transform infrared spectroscopy which indicated that the biomass had undergone drastic alterations and substantial disintegration due to pretreatment. The current study highlights the potential of combinative pretreatment strategy for efficient conversion of SCT biomass. Such combined pretreatment approaches may be extended to other biomass feedstocks as well for developing successful biorefineries.

Bacterial cellulose synthesized with apple pomace enhanced by ionic liquid pretreatment

Apple pomace was explored as alternative feedstock for producing bacterial cellulose (BC) by Gluconacetobacter xylinus following a cellulase saccharification performed after pretreatment of 1-allyl-3-methylimidazolium chloride ([AMIM]Cl). The dissolving process of apple pomace cellulose was observed by polarized light microscopy (PLM). As FT-IR and XRD results demonstrated, the IL pretreatment proved to be a physical process and no changes in the crystalline structure occurred during the pretreatment. However, the SEM result showed that more fissures and breakages appeared on the surface of pomace microfibers after IL-pretreating, which increased the contact area with cellulase and improved the enzymatic hydrolysis efficiency. An enhancing effect on the BC yield has been observed, 27% higher yield of BC obtained from hydrolysate as compared to sucrose-based medium indicates efficiency of IL-treated apple pomace to serve as high quality feedstock in BC production.

A facile ionic-liquid pretreatment method for the examination of archaeological wood by scanning electron microscopy

Wood has been a crucial natural material for human civilization since prehistoric times. In archaeology, the examination of the wood microstructure is important for the study of architecture, musical instruments, sculptures, and so on. Scanning electron microscopy (SEM) examination is sometimes unsuitable for archaeological wood due to the limited amount of precious samples, which may be too small to be cut by microtomes and mounted on holders. Moreover, the conductive coating material cannot be uniformly deposited over uneven wood surfaces. To overcome these issues, a rapid and simple pretreatment method using room-temperature ionic liquids (RTIL) was proposed. Four common RTILs were evaluated for the pretreatment of wood chips for SEM examination. We found that water content, viscosity, density, and hydrophobicity of IL solutions were important factors affecting SEM image quality. A 7.5% solution of 1-butyl-1-methylpyrrolidium dicyanamide (BMP-DCA) in ethanol (v/v) was found to work very well. The IL pretreatment could be performed in a few minutes without special equipment. It is gentle enough to preserve delicate structures such as the torus/margo of pit membranes, even at elevated temperatures, without causing obvious damage or deformation. We successfully imaged hand-cut wood chips from 18th-century buildings, an 18th-century European violin, and a Chinese zither over 1000 years old. We therefore conclude that highly hydrophilic ionic liquids with low density and viscosity are suitable for use in SEM examinations of both modern and antique wood specimens.

Methyltrioctylammonium chloride mediated removal of lignin from sugarcane bagasse for themostable cellulase production

The present study was aimed to evaluate the Methyltrioctylammonium Chloride (IL) and Sodium hydroxide effect on sugarcane bagasse (SB) structure and its subsequent utilization to produce cellulase from a thermophilic bacterium Bacillus aestuarii UE25. The strain was isolated from a crocodile pond of Manghopir, Karachi. Ten different factors affecting IL pretreatment of SB and cellulase production by UE25 were evaluated by Plackett-Burman design and three significant factors were optimized by employing Box Behnken design. Under optimum conditions, the strain produced 118.4 IU mL−1 of EG and 75.01 IU mL−1 of BGL that corroborated well with the predicted values by the model. Scanning electron microscopy, gravimetric analysis, Fourier transform infrared spectroscopy and NMR of SB revealed removal of lignin, decrease in cellulose content and structural changes in the SB after pretreatment and fermentation. The data provide prospects of utilizing this IL in comparison to imidazolium based IL for pretreatment of biomass.

A two-stage pretreatment using dilute sodium hydroxide solution followed by an ionic liquid at low temperatures: Toward construction of lignin-first biomass pretreatment

A two-stage pretreatment process is constructed to test the feasibility of lignin-first biomass pretreatment. It is expected that mild pretreatment conditions help to reduce structural alterations to lignin or minimize condensation reactions in lignin which are important for certain high value applications. The pretreatment process consists of a step using 1% sodium hydroxide solution to increase the porosity of biomass and a second step using a typical ionic liquid, 1-ethy-3-methylimidazolium acetate ([C2C1Im][OAc]), to transform native crystalline cellulose into amorphous cellulose and therefore enhance enzymatic hydrolysis efficiency. Both pretreatments are carried out at 60 °C for 3 h to lower the severity of the pretreatment. Lignin samples extracted from untreated biomass (Lignin 1), liquid phase after NaOH pretreatment (lignin 2), liquid phase after subsequent IL pretreatment (lignin 3) and the lignin remaining in pretreated biomass (lignin 4) were analyzed using FTIR and by measuring molecular weight and antioxidant properties.

Pretreatment of corn cob in [EMIM][OAc] and [EMIM][OAc]/ethanol (water).

High cost and high viscosity of ionic liquid restricted its commercial application in pretreatment of lignocellulose. Water and ethanol were used as additive in [EMIM][OAc] to pretreat corn cob at moderate temperature (< 100°C). It was found that enzyme hydrolysis (EH) sugar yield was increased with the increase of IL content. The largest EH sugar yield of 68.8% was obtained when pure IL was used. However, for [EMIM][OAc]/ethanol, the EH sugar yield as high as 66.9% was gained when the IL content was 80%, which was comparable to that for pure IL pretreatment. In addition, Kamlet-Taft parameter was calculated to characterize the polarity solvency of binary liquid phase, to illustrate the underlying reason for the increase of EH sugar and the lignin removal. Finally, to demonstrate the crystalline and microstructure change after pretreatment, XRD and SEM were performed for the raw materials and the pretreated samples.

Autohydrolysis and microwave ionic liquid pretreatment of Pinus radiata: Imaging visualization and analysis to understand enzymatic digestibility

Sequential pretreatments provide advantages of every single process towards a complete biomass fractionation. In this work, autohydrolysis and IL microwave pretreatments are sequentialy studied, and their effect to enhance enzymatic hydrolysis is analyzed. Mild, intermediate and severe autohydrolysis are combined with four IL temperatures (50, 80, 120 and 150 °C). Pretreated solids are enzymatically hydrolyzed and compared in terms of chemical composition and morphology. Digital image analysis is employed to numerically determine the heterogeneity of the solids using surface fractal dimension and lacunarity parameters. In this study, the negative effect of intermediate and severe autohydrolysis, over the subsequent IL pretreatment is demonstrated. Mild autohydrolysis and high IL conditions (AH150IL120) results in digestibilities of 78.8 g of glucan/100 g of glucan introduced. High surface fractal values (in the range of 2.5461–2.7124) and low lacunarities (0.0818–0.2563) enhance the enzymatic accessibility of pine wood. Furthermore, the negative effect of softwood lignin accumulation in the surface is observed using confocal fluorescence microscopy.

Extraction and Comparative Analysis of Lignin Extract from Alkali and Ionic Liquid Pretreatment

Lignin, a heterogenous polymer which presents about 20-30 % in lignocellulose emerged as promising feedstock for the production of specialty chemicals. However, due to lignocellulose recalcitrance structure, the pretreatment is necessary to obtain efficient utilization of biomass. In this work, the preliminary study was carried out focusing on the properties lignin extracted from bamboo (Gigantochloa scortcheninii) using alkali and ionic liquid pretreatment. It was discovered that about 42% and 11% of acid-insoluble lignin has been extracted from alkali and IL pretreatment respectively. The degradation onset temperature of alkali and ionic liquid extracted lignin were found to be 262.20 and 172.41°C. FTIR spectra analysis showed the characteristic peaks of lignin for both samples. Desirable products such as aldehydes, phenol, hydrocarbons and aromatics were identified from pyrolysis GC-MS

Pyridinium based ionic liquid: A pretreatment solvent and reaction medium for catalytic conversion of cellulose to total reducing sugars (TRS)

In the last decade, the transformation of lignocellulosic biomass into biofuel through a sugar platform has been an active research subject due to depletion of fossil fuel sources. Total reducing sugars (TRS) obtained from lignocellulosic materials are considered intermediates for the preparation of various valuable chemical compounds. In this work, pyridinium based ionic liquids were synthesized and utilized for the dissolution of cellulose and further conversion to TRS in the presence of metal salts as catalysts. The prepared ILs were characterized using 1H NMR and evaluated for the dissolution of cellulose and found that [C4C1Py][Cl] is the best solvent to dissolve it up to 28% at 110 °C. Optical microscopy in conjunction with FTIR, SEM, XRD and TGA analyses were employed to monitor dissolution phenomenon and ascertain structural changes in regenerated cellulose. SEM results showed disrupted flaky construction for regenerated cellulose. The thermal stability decreased for regenerated cellulose as observed by TGA analysis. This desirable change in cellulose after IL pretreatment was utilized to facilitate metal salts based on the catalytic conversion of cellulose to TRS. Among metal salts, CoCl2 was identified as the best one to generate the highest yield of TRS i.e. 78% at 110 °C for 4 h. Various reaction conditions like time, temperature, and catalyst loading were optimized for catalytic conversion. The optimum conditions were observed at 4 h treatment time, 120 °C and 12% catalyst loading.

Comparison of [HSO4]\u2212, [Cl]\u2212 and [MeCO2]\u2212 as anions in pretreatment of aspen and spruce with imidazolium-based ionic liquids

BackgroundIonic liquids (ILs) draw attention as green solvents for pretreatment of lignocellulose before enzymatic saccharification. Imidazolium-based ILs with different anionic constituents ([HSO4]−, [Cl]−, [MeCO2]−) were compared with regard to pretreatment of wood from aspen and spruce. The objective was to elucidate how the choice of anionic constituent affected the suitability of using the IL for pretreatment of hardwood, such as aspen, and softwood, such as spruce. The investigation covered a thorough analysis of the mass balance of the IL pretreatments, the effects of pretreatment on the cell wall structure as assessed by fluorescence microscopy, and the effects of pretreatment on the susceptibility to enzymatic saccharification. Torrefied aspen and spruce were included in the comparison for assessing how shifting contents of hemicelluloses and Klason lignin affected the susceptibility of the wood to IL pretreatment and enzymatic saccharification.ResultsThe glucose yield after IL pretreatment increased in the order [Cl]− < [HSO4]− < [MeCO2]− for aspen, but in the order [HSO4]− < [Cl]− < [MeCO2]− for spruce. For both aspen and spruce, removal of hemicelluloses and lignin increased in the order [Cl]− < [MeCO2]− < [HSO4]−. Fluorescence microscopy indicated increasingly disordered cell wall structure following the order [HSO4]− < [Cl]− < [MeCO2]−. Torrefaction of aspen converted xylan to pseudo-lignin and changed the glucose yield order to [HSO4]− < [Cl]− < [MeCO2]−.ConclusionsThe acidity of [HSO4]− caused extensive hydrolysis of xylan, which facilitated pretreatment of xylan-rich hardwood. Apart from that, the degree of removal of hemicelluloses and lignin did not correspond well with the improvement of the enzymatic saccharification. Taken together, the saccharification results were found to mainly reflect (i) the different capacities of the ILs to disorder the cell wall structure, (ii) the recalcitrance caused by high xylan content, and (iii) the capacity of the [HSO4]−-based IL to hydrolyze xylan.

A Novel Combined Pretreatment Method for Rice Straw Using Optimized EMIM[Ac] and Mild NaOH

Combined pretreatment methods for improving sugar yield as well as the economic aspects of lignoethanol production processes have gained a great deal of interest. However, most investigations involving such methods have been conducted under optimum conditions. Such fully-optimized combinations although improve enzymatic digestion, they could also degrade cellulose structure resulting in reduced sugar yield in some cases. The present study was set to prepare rice straw for the 1-ethyl-3-methylimidazolium acetate pretreatment step (2 h, 120 °C), by mild alkaline extraction (30 min, 80 °C, 0.3 % NaOH) with a focus on only 30 % lignin removal to minimize the hemicelluloses degradation. Moreover, the effect of size reduction (<0.42 mm and <2 cm) was also investigated. The results showed that the novel combination method based on only 30 % lignin removal led to an increased sugar yield by 17 %. Unexpectedly, although IL pretreatment needs material to be ground (<0.42 mm), the difference in sugar yields for the two sized tested was negligible. The overall lignocellolusic bioethanol production pathway including the combined AE–IL process proposed in the present study based on 30 % lignin removal through the first AE step.

English

The ionicliquid [MMIM][DMP] was synthesized from the reactants methyl imidazole [MIM] and trimethylphosphate [TMP] and verified using 1HNMR and FTIR. Coconut coir dust was pretreated with a 1% alkaline solution.Its crystalline structure increased significantly due to the dissolution of lignin and hemicelluloses under alkaline conditions, exposing the cellulose. After NaOH and IL were employed, the XRD showed that peak (002) decreased significantly and peak (101) almost vanished. This significant decrease in crystallinity was related to the alteration of the substrate from the cellulose I structure to the cellulose II structure. The pretreated substrates were hydrolyzed to convert them to reducing sugars by pure cellulase and xylanase,and the reaction was conducted at 60°C, pH 3, for 12 or 48 hours. The yields of sugar hydrolyzed from untreated and NaOH-pretreated substrates were 0.07 and 0.12 g sugar/g lignocellulose, respectively. Pretreatment with IL or the combination of NaOH+IL resulted in yields of reducing sugars of 0.11 and 0.13 g/g, respectively. These findings showed that IL pretreatment of the high-lignin lignocellulose is a new prospect for the economical manufacture of reducing sugars and bioethanol in the coming years.

Preparation of Reducing Sugar Hydrolyzed from High-Lignin Coconut Coir Dust Pretreated by the Recycled Ionic Liquid [mmim][dmp] and Combination with Alkaline

This study aims to produce reducing sugar hydrolyzed from substrate, coconut coir dust pretreated by recycled ionic liquid and its combination with alkaline. The 1H NMR and FTIR were performed to ver-ify the synthesized ionic liquid methylmethylimidazolium dimethyl phosphate ([mmim][dmp]). The structure of pretreated substrates was analyzed by XRD measurement. The used ionic liquid was recy-cled twice to re-employ for substrate pretreatment. The treated- and untreated-coconut coir dust were hydrolyzed into sugars using pure cellulase. The reaction, which called an enzymatic hydrolysis, was conducted at 60 °C, pH 3, for 48 h. The yields of sugar hydrolyzed from fresh IL-pretreated, 1R*IL-pretreated and 2R*IL-pretreated substrates were of 0.19, 0.15 and 0.15 g sugar / g cellu-lose+hemicellulose, respectively. Pretreatment with NaOH or the combination of NaOH+IL resulted in yields of reducing sugars of 0.25, 0.28 g/g, respectively. When alkaline combined with the recycled ionic liquids, NaOH+1R*IL, NaOH+2R*IL in the pretreatment, the yields of sugar were relatively similar to those obtained using alkaline followed by fresh ionic liquid. If the mixture enzymes, cellu-lase+xylanase, used to liberate sugars from fresh IL-pretreated, or recycled IL-pretreated substrates, the amount of sugar (concentration or yield) increased slightly compared to that employing a single cel-lulase. These findings showed that recycled IL pretreatment of the high-lignin lignocellulose, coconut coir dust, is a new prospect for the economical manufacture of fermentable sugars and biofuel in the coming years. © 2015 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Enhanced saccharification of lignocellulosic biomass with 1-allyl-3-methylimidazolium chloride (AmimCl) pretreatment

A simple and efficient method of enhancing biomass saccharification by microwave-assisted pretreatment with dimethyl sulfoxide/1-allyl-3-methylimidazolium chloride is proposed. Softwood (pine wood (PW)), hardwoods (poplar wood, catalpa bungi, and Chinese parasol), and agricultural wastes (rice straw, wheat straw, and corn stover (CS)) were exploited. Results showed that the best pretreatment effect was in PW with 54.3% and 31.7% dissolution and extraction ratios, respectively. The crystal form of cellulose in PW extract transformed from I to II, and the contended cellulose ratio and glucose conversion ratio reached 85.1% and 85.4%, respectively. CS after steam explosion achieved a similar pretreating effect as PW, with its cellulose hydrolysis ratio reaching as high as 91.5% after IL pretreatment. (C) 2014 Hui-Quan Li and Jian-Min Xing. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Scale-up and evaluation of high solid ionic liquid pretreatment and enzymatic hydrolysis of switchgrass

BackgroundIonic liquid (IL) pretreatment is receiving significant attention as a potential process that enables fractionation of lignocellulosic biomass and produces high yields of fermentable sugars suitable for the production of renewable fuels. However, successful optimization and scale up of IL pretreatment involves challenges, such as high solids loading, biomass handling and transfer, washing of pretreated solids and formation of inhibitors, which are not addressed during the development stages at the small scale in a laboratory environment. As a first in the research community, the Joint BioEnergy Institute, in collaboration with the Advanced Biofuels Process Demonstration Unit, a Department of Energy funded facility that supports academic and industrial entities in scaling their novel biofuels enabling technologies, have performed benchmark studies to identify key challenges associated with IL pretreatment using 1-ethyl-3-methylimidazolium acetate and subsequent enzymatic saccharification beyond bench scale.ResultsUsing switchgrass as the model feedstock, we have successfully executed 600-fold, relative to the bench scale (6 L vs 0.01 L), scale-up of IL pretreatment at 15% (w/w) biomass loading. Results show that IL pretreatment at 15% biomass generates a product containing 87.5% of glucan, 42.6% of xylan and only 22.8% of lignin relative to the starting material. The pretreated biomass is efficiently converted into monosaccharides during subsequent enzymatic hydrolysis at 10% loading over a 150-fold scale of operations (1.5 L vs 0.01 L) with 99.8% fermentable sugar conversion. The yield of glucose and xylose in the liquid streams were 94.8% and 62.2%, respectively, and the hydrolysate generated contains high titers of fermentable sugars (62.1 g/L of glucose and 5.4 g/L cellobiose). The overall glucan and xylan balance from pretreatment and saccharification were 95.0% and 77.1%, respectively. Enzymatic inhibition by [C2mim][OAc] at high solids loadings requires further process optimization to obtain higher yields of fermentable sugars.ConclusionResults from this initial scale up evaluation indicate that the IL-based conversion technology can be effectively scaled to larger operations and the current study establishes the first scaling parameters for this conversion pathway but several issues must be addressed before a commercially viable technology can be realized, most notably reduction in water consumption and efficient IL recycle.