Products Of Cellulose Hydrolysis Research Articles

Competitive Valerate Binding Enables RuO2-Mediated Butene Electrosynthesis in Water.

The (non)-Kolbe oxidation of valeric acid, sourced from a hydrolysis product of cellulose, provides a sustainable synthetic route to access value-added products, such as butene. An essential mechanistic step preceding product formation involves the oxidative and decarboxylative cleavage of a C-C bond. Yet, the role of the electrode surface in mediating this oxidative step remains an open question: the electron transfer can occur either via an inner-sphere or outer-sphere mechanism. Here, we report the electrochemical, in situ spectroscopic, computational, and reactivity studies of RuO2-mediated oxidative decarboxylation of valeric acid to butene in aqueous electrolytes. We find that carboxylates bind to RuO2 anode surfaces at potential values where decarboxylation products are observed. Our results are consistent with a reaction scheme where the competitive and catalytic oxygen evolution reaction (OER) is impeded by these bound carboxylate species while these species are inert toward butene formation. Our results implicate an outer-sphere electron transfer mechanism for decarboxylation where the surface chemistry of the RuO2 electrode serves to enable higher non-Kolbe reaction selectivity by suppressing the parasitic OER. Our findings delineate interfacial design principles for selective electrochemical systems that utilize water as the ultimate oxidant for sustainable decarboxylation.

Cellobiose elicits immunity in lettuce conferring resistance to Botrytis cinerea.

Cellobiose is the primary product of cellulose hydrolysis and is expected to function as a type of pathogen/damage-associated molecular pattern in evoking plant innate immunity. In this study, cellobiose was demonstrated to be a positive regulator in the immune response of lettuce, but halted autoimmunity when lettuce was exposed to concentrations of cellobiose >60 mg l-1. When lettuce plants were infected by Botrytis cinerea, cellobiose endowed plants with enhanced pre-invasion resistance by activating high β-1,3-glucanase and antioxidative enzyme activities at the initial stage of pathogen infection. Cellobiose-activated core regulatory factors such as EDS1, PTI6, and WRKY70, as well as salicylic acid signaling, played an indispensable role in modulating plant growth-defense trade-offs. Transcriptomics data further suggested that the cellobiose-activated plant-pathogen pathways are involved in microbe/pathogen-associated molecular pattern-triggered immune responses. Genes encoding receptor-like kinases, transcription factors, and redox homeostasis, phytohormone signal transduction, and pathogenesis-related proteins were also up- or down-regulated by cellobiose. Taken together, the findings of this study demonstrated that cellobiose serves as an elicitor to directly activate disease-resistance-related cellular functions. In addition, multiple genes have been identified as potential modulators of the cellobiose-induced immune response, which could aid understanding of underlying molecular events.

Amperometric method for the determination of cellulase activity and its optimization using response surface method

Cellulases are a group of enzymes, which catalyse different steps of cellulose hydrolysis, and are broadly used in industry as unpurified mixtures of several enzymes. The total activity of cellulase is defined as the ability of the enzyme to produce glucose, which is the final product of cellulose hydrolysis, and is expressed in cellulase units. However, common strategies for the determination of the cellulolytic activity of industrial cellulase preparations are based on the assessment of different steps of cellulose hydrolysis, and the results obtained with different methods are not similar. The aim of the present study was to develop an assay for the determination of cellulase activity that relies on the amperometric determination of the final product of cellulose hydrolysis glucose. The assay conditions were optimized using response surface methodology (RSM) combined with Box-Behnken design. The detection limit of the proposed method was 1.71 ± 0.06 U. We compared the results of the amperometric method with the ones obtained with the spectrophotometric method and viscosimetry in a commercial cellulose preparation.

Carbon dots derived from cellobiose for temperature and phosalone detection

Cellobiose, the hydrolysis product of cellulose and the dimer of glucose, was employed to synthesize carbon dots (CDs) via a simple hydrothermal method. The inducing of nitrogen can act as a “molecular glue”, more and more carbon clusters were “glued” together, which would push the hydrothermal reaction in the positive direction. Besides, the linear response of the fluorescence of N-CDs to temperature ensured its potential application in temperature sensing. In the temperature range of 10∼80 °C, the fluorescence of as-prepared N-CDs was reversible and recoverable. Moreover, the dual fluorescence centers and dual-absorption bands of the as-prepared N-CDs permitted the novel dual-mode ratiometric assays for phosalone detection. The linear range and limit of detection (LOD) for dual fluorescence center-based ratiometric assay were 0.12∼5.45 μg/mL and 42.90 ng/mL, respectively. While that for the dual absorption-based ratiometric assay were 0.02∼1.40 μg/mL, and 6.67 ng/mL, respectively.

Enzymatic hydrolysis of cellulose using extracts from insects

The use of Zophobas morio extracts in the aspect of cellulose hydrolysis is presented for the first time. The aim of this study was to investigate the action of enzymes obtained from Z. morio on cellulose hydrolysis and to determine their influence on the structural properties of cellulose with use the Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). Cellulose hydrolysis products were analyzed by high performance liquid chromatography (HPLC). This analysis indicated that microcrystalline cellulose with smaller particle size was more susceptible to enzymatically treatment.Moreover, our investigation of cellulase activity showed a different profile of the used enzyme during particular developmental stages of Z. morio. Midgut extracts obtained from adult insects are more effective in degrading cellulose than extracts from larvae. The analysis of cellulose hydrolysis confirms that the efficiency of this reaction also depends on the structure of cellulosic materials and internal conditions of enzymatic reaction. In this study the cellulolytic activity of Z. morio midgut extracts showed that these insects could be valuable sources of cellulases.

Biochemical Characterization of a Novel Monospecific Endo-β-1,4-Glucanase Belonging to GH Family 5 From a Rhizosphere Metagenomic Library.

Cellulases have a broad range of different industrial applications, ranging from food and beverages to pulp and paper and the biofuels area. Here a metagenomics based strategy was used to identify the cellulolytic enzyme CelRH5 from the rhizosphere. CelRH5 is a novel monospecific endo-β-1,4-glucanase belonging to the glycosyl hydrolase family 5 (GH5). Structural based modeling analysis indicated that CelRH5 is related to endo-β-1,4-glucanases derived from thermophilic microorganisms such as Thermotoga maritima, Fervidobacterium nodosum, and Ruminiclostridium thermocellum sharing 30-40% amino acid sequence identity. The molecular weight of the enzyme was determined as 40.5 kDa. Biochemical analyses revealed that the enzyme displayed good activity with soluble forms of cellulose as a substrate such as ostazin brilliant red hydroxyethyl cellulose (OBR-HEC), carboxymethylcellulose (CMC), hydroxyethyl cellulose (HEC), and insoluble azurine cross-linked hydroxyethylcellulose (AZCL-HEC). The enzyme shows highest enzymatic activity at pH 6.5 with high pH tolerance, remaining stable in the pH range 4.5–8.5. Highest activity was observed at 40°C, but CelRH5 is psychrotolerant being active and stable at temperatures below 30°C. The presence of the final products of cellulose hydrolysis (glucose and cellobiose) or metal ions such as Na+, K+, Li+, and Mg2+, as well as ethylenediaminetetraacetic acid (EDTA), urea, dithiothreitol (DTT), dimethyl sulfoxide (DMSO), 2-mercaptoethanol (2-ME) or glycerol, did not have a marked effect on CelRH5 activity. However, the enzyme is quite sensitive to the presence of 10 mM ions Zn2+, Ni2+, Co2+, Fe3+ and reagents such as 1 M guanidine HCl, 0.1% sodium dodecyl sulfate (SDS) and 20% ethanol. Given that it is psychrotolerant and retains activity in the presence of final cellulose degradation products, metal ions and various reagents, which are common in many technological processes; CelRH5 may be potential suitability for a variety of different biotechnological applications.

Anaerobacillus isosaccharinicus sp. nov., an alkaliphilic bacterium which degrades isosaccharinic acid.

Strain NB2006T was isolated from an isosaccharinate-degrading, nitrate-reducing enrichment culture in minimal freshwater medium at pH 10. Analysis of the 16S rRNA gene sequence indicated that this strain was most closely related to species of the newly established genus Anaerobacillus. This was supported by phenotypic and metabolic characterisation that showed that NB2006T was rod-shaped, Gram-stain-positive, motile and formed endospores. It was an aerotolerant anaerobe and an obligate alkaliphile that grew at pH 8.5-11, could tolerate up to 6 % (w/v) NaCl, and grew at a temperature between 10 and 40 °C. In addition, it could utilise a number of organic substrates, and was able to reduce nitrate and arsenate. The predominant cellular fatty acids were C16 : 0, C16 : 1ω11c, anteiso-C15 : 0, iso-C15 : 0, C16 : 1ω7c/iso-C15 : 0 2-OH and C14 : 0. The cell wall peptidoglycan contained meso-diaminopimelic acid and the DNA G+C content was 37.7 mol%. In silico DNA-DNA hybridization with the four known species of the genus Anaerobacillus showed 21.8, 21.9, 22.4, and 21.5 % relatedness to Anaerobacillusarseniciselenatis DSM 15340T, Anaerobacilus alkalidiazotrophicus DSM 22531T, Anaerobacillusalkalilacustris DSM 18345T, and Anaerobacillus macyae DSM 16346T, respectively. NB2006T differed from strains of other species of the genus Anaerobacillus in its ability to metabolise isosaccharinate, an alkaline hydrolysis product of cellulose. On the basis of the consensus of phylogenetic and phenotypic analyses, this strain represents a novel species of the genus Anaerobacillus, for which the name Anaerobacillus isosaccharinicus sp. nov. is proposed. The type strain is NB2006T (=DSM 100644T=LMG 30032T).

Kinetics and Modelling of Levulinic Acid Esterification in Batch and Continuous Reactors

The ethyl ester of levulinic acid, ethyl levulinate is a completely bio-based chemical made from levulinic acid, which is a hydrolysis product of cellulose and bio-ethanol. The very precise kinetics of levulinic acid esterification with ethanol was studied in an isothermal batch reactor in the presence of homogeneous (H2SO4) and heterogeneous catalysts (cation exchange resin Smopex-101). The temperature interval of the experiments was 50–70 °C. A kinetic model was proposed for both kinds of catalysts, adopting equilibrium rate expressions in any case. The different role of the catalyst used was considered separately, while a unique equilibrium constant was assumed for each system. The kinetic parameters were successfully determined by non-linear regression analysis. The model gave a very good description to the experimental data. The heterogeneous catalyst was used to demonstrate the feasibility of continuous operation in isothermal fixed bed reactors. The catalyst showed a good stability and high conversions of levulinic acid were obtained in the laboratory-scale fixed bed reactor. The model was able to predict both dynamic and steady-state experimental data.

Solvent effect of gamma-valerolactone (GVL) on cellulose and biomass hydrolysis in hot-compressed GVL/water mixtures

This study employs a semi-continuous reactor system to investigate the solvent effect of gamma-valerolactone (GVL) on cellulose hydrolysis in hot-compressed GVL/water (HCGW) at 250 °C and 10 MPa. The primary liquid products from cellulose hydrolysis in HCGW at various GVL concentrations are collected and characterised. Both hydrolysis reaction rate and final glucose recovery are found to increase with GVL concentration, with a high glucose recovery of 91% achieved in the primary liquid products of cellulose hydrolysis in 10% GVL/water. Further analyses of the primary liquid products using high performance anion exchange chromatography with pulsed amperometric detection show the reductions in the isomers of glucose oligomers (with reducing end as fructose and mannose) and the increases in the glucose oligomers with low degrees of polymerisation, indicating that GVL addition enhances hydrolysis reactions but suppresses isomerization reactions in the solid phase. Similar effects are also found in the secondary reactions of the primary liquid products during cellulose hydrolysis at reduced flow rates. The experimental results from biomass hydrolysis clearly demonstrate that GVL/water co-solvent is an excellent reaction medium for biomass hydrolysis under acid-free conditions, achieving a near-complete sugar recovery (i.e., 93%) at a low GVL concentration of 5%.

A seven-gene cluster in Ruminiclostridium cellulolyticum is essential for signalization, uptake and catabolism of the degradation products of cellulose hydrolysis

BackgroundLike a number of anaerobic and cellulolytic Gram-positive bacteria, the model microorganism Ruminiclostridium cellulolyticum produces extracellular multi-enzymatic complexes called cellulosomes, which efficiently degrade the crystalline cellulose. Action of the complexes on cellulose releases cellobiose and longer cellodextrins but to date, little is known about the transport and utilization of the produced cellodextrins in the bacterium. A better understanding of the uptake systems and fermentation of sugars derived from cellulose could have a major impact in the field of biofuels production.ResultsWe characterized a putative ABC transporter devoted to cellodextrins uptake, and a cellobiose phosphorylase (CbpA) in R. cellulolyticum. The genes encoding the components of the ABC transporter (a binding protein CuaA and two integral membrane proteins) and CbpA are expressed as a polycistronic transcriptional unit induced in the presence of cellobiose. Upstream, another polycistronic transcriptional unit encodes a two-component system (sensor and regulator), and a second binding protein CuaD, and is constitutively expressed. The products might form a three-component system inducing the expression of cuaABC and cbpA since we showed that CuaR is able to recognize the region upstream of cuaA. Biochemical analysis showed that CbpA is a strict cellobiose phosphorylase inactive on longer cellodextrins; CuaA binds to all cellodextrins (G2–G5) tested, whereas CuaD is specific to cellobiose and presents a higher affinity to this sugar. This results are in agreement with their function in transport and signalization, respectively. Characterization of a cuaD mutant, and its derivatives, indicated that the ABC transporter and CbpA are essential for growth on cellobiose and cellulose.ConclusionsFor the first time in a Gram-positive strain, we identified a three-component system and a conjugated ABC transporter/cellobiose phosphorylase system which was shown to be essential for the growth of the model cellulolytic bacterium R. cellulolyticum on cellobiose and cellulose. This efficient and energy-saving system of transport and phosphorolysis appears to be the major cellobiose utilization pathway in R. cellulolyticum, and seems well adapted to cellulolytic life-style strain. It represents a new way to enable engineered strains to utilize cellodextrins for the production of biofuels or chemicals of interest from cellulose.

Pressure and temperature effect on cellulose hydrolysis in pressurized water

In this study, the effect of temperature and pressure on cellulose and glucose hydrolysis in a hydrothermal media was analyzed. To do so, cellulose hydrolysis experiments were carried out in a continuous pilot plant capable of operating up to 400°C and 27MPa. The reaction times were varied between 0.004 and 40s. The main products of cellulose hydrolysis were oligosaccharides, cellobiose, glucose and fructose. The concentration profiles of each component followed a similar behavior at a fixed temperature changing pressure. Nevertheless, glucose and fructose hydrolysis reaction to give dehydration of retro aldol condensation products were strongly affected by pressure and temperature. When increasing temperature in the studied range, the reaction of glucose isomerization to fructose and the production of 5-hydroxymethylfurfural (5-HMF) obtained through fructose dehydration were inhibited. On the other hand, 5-HMF production was favored by high proton concentrations due to water dissociation. Thus, at a constant temperature, the production of 5-HMF was increased by rising the ionic product of water (increasing pressure). The production of glycolaldehyde (retro-aldol condensation of glucose) was increased by rising temperature and pressure. The kinetic constants of the cellulose hydrolysis reactions were determined at the experimented conditions using the experimental results. The kinetic constants were plotted against temperature and pressure to determine the activation energy and the activation volume for each reaction, respectively. Pressure seems to have no effect on the cellulose hydrolysis kinetic to simple sugars. However, at supercritical water temperatures the increment in pressure disfavored the glucose isomerization and dehydration reactions.

Analysis of cellodextrin transporters from Neurospora crassa in Saccharomyces cerevisiae for cellobiose fermentation

Saccharomyces cerevisiae can be engineered to ferment cellodextrins produced by cellulases as a product of cellulose hydrolysis. Direct fermentation of cellodextrins instead of glucose is advantageous because glucose inhibits cellulase activity and represses the fermentation of non-glucose sugars present in cellulosic hydrolyzates. To facilitate cellodextrin utilization by S. cerevisiae, a fungal cellodextrin-utilizing pathway from Neurospora crassa consisting of a cellodextrin transporter and a cellodextrin hydrolase has been introduced into S. cerevisiae. Two cellodextrin transporters (CDT-1 and CDT-2) were previously identified in N. crassa, but their kinetic properties and efficiency for cellobiose fermentation have not been studied in detail. In this study, CDT-1 and CDT-2, which are hypothesized to transport cellodextrin with distinct mechanisms, were introduced into S. cerevisiae along with an intracellular β-glucosidase (GH1-1). Cellobiose transport assays with the resulting strains indicated that CDT-1 is a proton symporter while CDT-2 is a simple facilitator. A strain expressing CDT-1 and GH1-1 (DCDT-1G) showed faster cellobiose fermentation than the strain expressing CDT-2 and GH1-1 (DCDT-2G) under various culture conditions with different medium compositions and aeration levels. While CDT-2 is expected to have energetic benefits, the expression levels and kinetic properties of CDT-1 in S. cerevisiae appears to be optimum for cellobiose fermentation. These results suggest CDT-1 is a more effective cellobiose transporter than CDT-2 for engineering S. cerevisiae to ferment cellobiose.

Purification and biochemical characterization of glucose–cellobiose-tolerant cellulases from Scytalidium thermophilum

Two cellulases from Scytalidium thermophilum were purified and characterized, exhibiting tolerance to glucose and cellobiose. Characterization of purified cellulases I and II by mass spectrometry revealed primary structure similarities with an exoglucanase and an endoglucanase, respectively. Molecular masses were 51.2 and 45.6kDa for cellulases I and II, respectively, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Cellulases I and II exhibited isoelectric points of 6.2 and 6.9 and saccharide contents of 11 and 93%, respectively. Optima of temperature and pH were 60-65°C and 4.0 for purified cellulase I and 65°C and 6.5 for purified cellulase II. Both cellulases maintained total CMCase activity after 60min at 60°C. Cysteine, Mn(2+), dithiotreitol and ß-mercaptoethanol-stimulated cellulases I and II. The tolerance to cellulose hydrolysis products and the high thermal stabilities of Scytalidium cellulases suggest good potential for industrial applications.

Form and Function of Clostridium thermocellum Biofilms

The importance of bacterial adherence has been acknowledged in microbial lignocellulose conversion studies; however, few reports have described the function and structure of biofilms supported by cellulosic substrates. We investigated the organization, dynamic formation, and carbon flow associated with biofilms of the obligately anaerobic cellulolytic bacterium Clostridium thermocellum 27405. Using noninvasive, in situ fluorescence imaging, we showed biofilms capable of near complete substrate conversion with a characteristic monolayered cell structure without an extracellular polymeric matrix typically seen in biofilms. Cell division at the interface and terminal endospores appeared throughout all stages of biofilm growth. Using continuous-flow reactors with a rate of dilution (2 h(-1)) 12-fold higher than the bacterium's maximum growth rate, we compared biofilm activity under low (44 g/liter) and high (202 g/liter) initial cellulose loading. The average hydrolysis rate was over 3-fold higher in the latter case, while the proportions of oligomeric cellulose hydrolysis products lost from the biofilm were 13.7% and 29.1% of the total substrate carbon hydrolyzed, respectively. Fermentative catabolism was comparable between the two cellulose loadings, with ca. 4% of metabolized sugar carbon being utilized for cell production, while 75.4% and 66.7% of the two cellulose loadings, respectively, were converted to primary carbon metabolites (ethanol, acetic acid, lactic acid, carbon dioxide). However, there was a notable difference in the ethanol-to-acetic acid ratio (g/g), measured to be 0.91 for the low cellulose loading and 0.41 for the high cellulose loading. The results suggest that substrate availability for cell attachment rather than biofilm colonization rates govern the efficiency of cellulose conversion.

High-yield production of meso-2,3-butanediol from cellodextrin by engineered E. coli biocatalysts

Escherichia coli has been engineered to produce a variety of biofuel and biorefinery products. However, it can only produce these products from simple sugars, requiring large amounts of enzymes to depolymerize cellulose into monomer sugars. Engineering E. coli to directly use cellodextrin, the partial hydrolysis product of cellulose, potentially could reduce the requirement of enzyme thereby the overall cost. Through a combination of gene deletion, introduction of a synthetic operon, and periplasmic expression of a Saccharophagus cellodextrinase, we engineered, for the first time, an E. coli biocatalyst capable of producing BDO from cellodextrin. The success of the engineering strategy is evidenced by the high BDO yield (>80%) from cellodextrin. We additionally demonstrate that the engineered biocatalyst can be advantageously used in a SSF process for BDO production from cellulose as the expression of cellodextrinase from a BDO producer augments the insufficient β-glucosidase activities in a commercial cellulase cocktail.

Evaluation of nanoparticle‐immobilized cellulase for improved ethanol yield in simultaneous saccharification and fermentation reactions

Ethanol yields were 2.1 (P = 0.06) to 2.3 (P = 0.01) times higher in simultaneous saccharification and fermentation (SSF) reactions of microcrystalline cellulose when cellulase was physisorbed on silica nanoparticles compared to enzyme in solution. In SSF reactions, cellulose is hydrolyzed to glucose by cellulase while yeast simultaneously ferments glucose to ethanol. The 35°C temperature and the presence of ethanol in SSF reactions are not optimal conditions for cellulase. Immobilization onto solid supports can stabilize the enzyme and promote activity at non-optimum reaction conditions. Mock SSF reactions that did not contain yeast were used to measure saccharification products and identify the mechanism for the improved ethanol yield using immobilized cellulase. Cellulase adsorbed to 40 nm silica nanoparticles produced 1.6 times (P = 0.01) more glucose than cellulase in solution in 96 h at pH 4.8 and 35°C. There was no significant accumulation (<250 µg) of soluble cellooligomers in either the solution or immobilized enzyme reactions. This suggests that the mechanism for the immobilized enzyme's improved glucose yield compared to solution enzyme is the increased conversion of insoluble cellulose hydrolysis products to soluble cellooligomers at 35°C and in the presence of ethanol. The results show that silica-immobilized cellulase can be used to produce increased ethanol yields in the conversion of lignocellulosic materials by SSF.

Isolation and characterization of a new cellulosome-producing Clostridium thermocellum strain

The anaerobic thermophilic bacterium, Clostridium thermocellum, is a potent cellulolytic microorganism that produces large extracellular multienzyme complexes called cellulosomes. To isolate C. thermocellum organisms that possess effective cellulose-degrading ability, new thermophilic cellulolytic strains were screened from more than 800 samples obtained mainly from agriculture residues in Thailand using microcrystalline cellulose as a carbon source. A new strain, C. thermocellum S14, having high cellulose-degrading ability was isolated from bagasse paper sludge. Cellulosomes prepared from S14 demonstrated faster degradation of microcrystalline cellulose, and 3.4- and 5.6-fold greater Avicelase activity than those from C. thermocellum ATCC27405 and JW20 (ATCC31449), respectively. Scanning electron microscopic analysis showed that S14 had unique cell surface features with few protuberances in contrast to the type strains. In addition, the cellulosome of S14 was resistant to inhibition by cellobiose that is a major end product of cellulose hydrolysis. Saccharification tests conducted using rice straw soaked with sodium hydroxide indicated the cellulosome of S14 released approximately 1.5-fold more total sugars compared to that of ATCC27405. This newly isolated S14 strain has the potential as an enzyme resource for effective lignocellulose degradation.

Effect of ball milling on the hydrolysis of microcrystalline cellulose in hot‐compressed water

AbstractBall milling leads to a considerable reduction in cellulose particle size and crystallinity, as well as a significant increase in the specific reactivity of cellulose during hydrolysis in hot‐compressed water (HCW). Cryogenic ball milling for 2 min also results in a significant size reduction but only little change in cellulose crystallinity and specific reactivity during hydrolysis. Therefore, crystallinity is the dominant factor in determining the hydrolysis reactivity of cellulose in HCW while particle size only plays a minor role. Ball milling also significantly influences the distribution of glucose oligomers in the primary liquid products of cellulose hydrolysis. It increases the selectivities of glucose oligomers at low conversions. At high conversions, the reduction in chain length plays an important role in glucose oligomer formation as cellulose samples become more crystalline. An extensive ball milling completely converts the crystalline cellulose into amorphous cellulose, substantially enhancing the formation of glucose oligomers with high degrees of polymerization. © 2010 American Institute of Chemical Engineers AIChE J, 2011

Direct conversion and NMR observation of cellulose to glucose and 5-hydroxymethylfurfural (HMF) catalyzed by the acidic ionic liquids

The hydrolysis of cellulose was catalyzed over a variety of acidic ionic liquids (ILs). It is found that the hydrolysis activity is directly associated with the acidity of catalysts, as evidenced by IR spectroscopy. 13C NMR characterization results confirm the majority product of cellulose hydrolysis is glucose, and the resulting carbohydrates undergo further degradation, possibly also catalyzed by the acidic ILs, to 5-hydroxymethylfurfural (HMF). Moreover, in situ13C NMR measurements clearly exhibit that the evolution of products is dependent on the reaction process. We attempt to study the kinetics of cellulose hydrolysis over the most active catalyst of [C4SO3Hmim]HSO4 at different temperatures (80–120°C) to obtain the important kinetic parameters such as apparent activation energies of consecutive reaction steps.

Understanding the Primary Liquid Products of Cellulose Hydrolysis in Hot-Compressed Water at Various Reaction Temperatures

Knowledge on the primary liquid products is essential to understanding the primary hydrolysis reactions that take place on the surface of microcrystalline cellulose particles during hydrolysis in hot-compressed water (HCW). This study reports the experimental results on the primary liquid products from the hydrolysis of cellulose using a semicontinuous reactor system under optimized reaction conditions. The primary liquid products contain glucose oligomers and their derivatives with a wide range of degrees of polymerization (DPs), from 1 to a maximal DP, which increases with temperature from 23 at 230 °C, to 25 at 250 °C, then to 28 at 270 °C. Temperature also has a significant influence on the distribution of glucose oligomers in the primary liquid products. The results suggest that the hydrolysis reactions proceed on the surface of reacting cellulose particles via the cleavage of the accessible glycosidic bonds within the structure of microcrystalline cellulose in a manner with randomness. Thermal degra...