对“纤维素水解”演示实验的改进

高中化学新教材（试验修订本·必修加选修）第185页[实验7-5]“纤维素水解”的演示实验，是高中化学的重要实验．也是一个疑难实验。做好这个实验对于引导学生学好纤维素的重要性质起着非常关键的作用。教材中采用90％浓硫酸滴到棉花或滤纸上，再用玻璃棒把棉花或滤纸捣成糊状。小火微热直到溶液变成亮棕色，最后加新制的Cu（OH）2加热煮沸。但是在实际操作中，很难成功，实验现象也不明显，溶液经常由于硫酸浓度过高而被炭化成黑色，看不到亮棕色，最后加新制的Cu（OH）2，加热煮沸也看不到砖红色的沉淀出现。

Preparation of 5-Hydroxymethylfurfural from Cellulose via Fast Depolymerization and Consecutively Catalytic Conversion

The conversion of cellulose to 5-hydroxymethylfurfural （HMF） has been investigated by a one-pot consecutive reaction. At first, cellulose was depolymerised into glucose via a fast degradation of cellulose in molten ZnCI~ in the presence of hydrochloric acid, and the yield of glucose is 75% in 120 s at reaction temperature of 95 ℃. Then, DMSO was used as solvent and different kinds of metal chloride were added as catalysts, and the conversion was carried out continuously at 110-130 ℃ for 0.5-4 h. The yield of HMF was 53% when CrC13 were used as catalyst. The one-pot two steps conversion was carried out at atmosphere pressure, and it is a simple route to prepare HMF from lignocellulosic feedstock on a large scale.

Efficient and Comprehensive Utilizatio℃n of Hemicellulose in the Corn Stover

Pretreatment of the corn stover powder by dilute sulphuric acid （solid-liquid ratio 1 ： 20） at 130 for 30 min was carried out with 89.09% of the hemicellulose removed. After filtration, the xylose-rich corn stover pretreatment liquid, whose fermentable sugar was from hemicellulose hydrolysis only, consisting of 81.16% xylose and 15.27% glucose, was used to cultivate genetic recombinant Escherichia coli BL21 with human-like collagen （HLC） expression enhanced by 50.00% and 63.71% xylose consumption.

Enzymatic Hydrolysis of Cellulose with Different Crystallinities Studied by Means of SEC-MALLS

The reactions of exo-cellulase （cellobiohydrolase, CBH） and endo-cellulase （endoglucanase, EG） were investigated by analyzing the insoluble residues of microcrystalline cellulose （MCC） and filter paper cellulose （FPC） during enzymatic hydrolysis. Molecular parameters including molecular weight and its distribution, degree of polymerization, and radii of gyration were measured by size exclusion chromatography coupled with multi-angle laser light scattering. No significant change in MCC chains was found during the whole reaction period, indicating that CBH digestion follows a layer-by-layer solubilization manner. This reaction mode might be the major reason for slow enzymatic hydrolysis of cellulose. On the other hand, the degree of polymerization of FPC chains decreases rapidly in the initial reaction, indicating that EG digestion follows a random scission manner, which may create new ends for CBH easily. The slopes of the conformation plots for MCC and FPC increase gradually, indicating stronger chain stiffness of cellulose during hvdrolvsis

Pretreatment of Corn Stover Using Supercritical CO2 with Water-Ethanol as Co-solvent

Supercritical carbon dioxide,with water-ethanol as co-solvent,was applied to pretreat corn stover to enhance its enzymatic hydrolysis.The efficiency of pretreatment was evaluated by the final reducing sugar yield obtained from the enzymatic hydrolysis of cellulose.Under the operation conditions of pretreatment pressure 15 MPa,temperature 180 ℃ and time 1 h,the optimal sugar yield of 77.8℅ was obtained.Scanning electron microscopy(SEM) and chemical composition analysis were applied to the pretreated corn stover.The results showed that the surface morphology and microscopic structure of pretreated corn stover were greatly changed.After the pretreatment,the contents of hemicellulose and lignin were reduced obviously.Thus more cellulose was exposed,increasing the sugar yield.

Biorefinery of bacterial cellulose from rice straw:enhanced enzymatic saccharification by ionic liquid pretreatment

The pretreatment of rice straw is often used to enhance the hydrolysis. 1-allyl-3-methylimidazolium chloride （ [ AMIM ] C1） is a kind of low viscous, nontoxic and recyclable ionic liquid. It was used to treat rice straw and improve the enzymatic hydrolysis of rice straw in this study. The factors influencing the pretreatment were as follows： the dosage of rice straw in [ AMIM ] Cl, crush mesh of rice straw, pretreatment temperature and time. After the pretreatment with a 3 % （the weight ratio of rice straw to ionic liquid） rice straw dosage in [AMIM]Cl at 110 ℃ for 1 h, the yield of reducing sugar of regenerated rice straw by 33 U/mL cellulase hydrolysis was 53.3 %, which was two times higher than that of un-treated rice straw （23.7 % ）. More researches regarding straw biorefinery to bacterial cellulose are being performed in the lab and prospective results will be published in near future.

Production of bio-ethanol by consecutive hydrogenolysis of corn-stalk cellulose

Current bio-ethanol production entails the enzymatic depolymerization of cellulose,but this process shows low efficiency and poor economy.In this work,we developed a consecutive aqueous hydrogenolysis process for the conversion of corn-stalk cellulose to produce a relatively high concentration of bio-ethanol(6.1 wt%)without humin formation.A high yield of cellulose(ca.50 wt%)is extracted from corn stalk using a green solvent(80 wt%1,4-butanediol)without destroying the structure of the lignin.The first hydrothermal hydrogenolysis step uses a Ni–WO_(x)/SiO_(2)catalyst to convert the high cumulative concentration of cellulose(30 wt%)into a polyol mixture with a 56.5 C%yield of ethylene glycol(EG).The original polyol mixture is then subjected to subsequent selective aqueous-phase hydrogenolysis of the C–O bond to produce bioethanol(75%conversion,84 C%selectivity)over the modified hydrothermally stable Cu catalysts.The added Ni component favors the good dispersion of Cu nanoparticles,and the incorporated Au3+helps to stabilize the active Cu^(0)-Cu^(+)species.This multi-functional catalytic process provides an economically competitive route for the production of cellulosic ethanol from raw lignocellulose.

Cascade Enzymatic Hydrolysis Coupling with Ultrafine Grinding Pretreatment for Sugarcane Bagasse Saccharification

The biorefinery process for sugarcane bagasse saccharification generally requires signifcant accessibility of cellulose. We reported a novel method of cascade cellulase enzymatic hydrol- ysis coupling with ultrafine grinding pretreatment for sugarcane bagasse saccharification. Three enzymatic hydrolysis modes including single cellulase enzymatic hydrolysis, mixed cellulase enzymatic hydrolysis, and cascade cellulase enzymatic hydrolysis were compared. The changes on the functional group and surface morphology of bagasse during cascade cellulase enzymatic hydrolysis were also examined by FT-IR and SEM respectively. The results showed that cascade enzymatic hydrolysis was the most efficient way to enhance the sugarcane bagasse saccharification. More than 65% of reducing sugar yield with 90.1% of glucose selectivity was achieved at 50 ℃, pH=4.8 for 72 h （1200 r/min） with cellulase I of 7.5 FPU/g substrate and cellulase II of 5 FPU/g substrate.

Decomposition of Cellulose by Continuous Near-Critical Water Reactions

A pilot-scale apparatus for continuous supercritical and near-critical water reaction was set up. A high-pressure slurry supplying system was developed to feed the solid material-water slurries. The apparatus features temperature up to 600℃, pressure up to 40MPa, residence time from 24s to 15min, maximum amount of slurry supply of 2.4 L·h-1, maximum solid content of slurry up to 10%(by mass) for cellulose from Merck, and resistance to corrosion. Long-time runs of decomposition of cellulose were carried out and steady runs were confirmed. Kinetics of cellulose decomposition was studied. The apparent activation energy evaluated was 147kJ·mol-1. In addition, a new three-step pathway for cellulose hydrolysis was proposed. The derived kinetic equation is in good agreement with the experimental data.

Study of cellulolytic soil fungi and two nova species and new medium

This study is aimed at identifying and determining the percentage of occurrence frequency of cellulose decomposing soil fungi. The soil samples were inoculated into culture plates prepared in Sabouraud medium under sterilized conditions and incubated at 30 ℃ for 4 to 7 d. The identified fungal species were incubated in self-designed cellulose medium for testing their cellulolytic ability. Forty-two species, including2 nova species, representing sixteen genera showed growth and sporulation in the cellulose medium. Most of the isolated species were from genus Aspergillus and Penicillium. Aspergillus niger and Mucor hiemalis showed highest occurrence frequency （45% and 36% respectively）, as these species were collected from about 80% of soil samples. Being agar free and cheaper, the new fungal medium designed showed results equivalent to Sabouraud medium.

Green Modification of Cellulose Nanocrystals and Their Reinforcement in Nanocomposites of Polylactic Acid

Cellulose nanocrystals （CNCs） of rod-like shape were prepared from degreased cotton using sulfuric acid hydrolysis. The obtained CNC suspension was neutralized using a sodium hydroxide solution to remove the residual sulfuric acid and improve the thermal stability of the CNC particles. Then, poly（ethylene oxide） （PEO） was employed to modify the nanocrystals through entanglement and physical adsorption. The goal was to further improve the thermal stability and weaken the hydrophilicity of CNCs. Original and modifed CNCs were dosed into a polylactic acid （PLA） matrix to prepare nanocomposites using a hot compression process. Results of the thermogravimetric analysis showed that the initial thermal decomposition temperature of the modifed CNCs showed a 120℃ improvement compared to the original CNCs. That is, the thermal stability of the modified CNCs improved because of their shielding and wrapping by a PEO layer on their surface. Results from scanning electron microscopy and ultraviolet-visible spectrophotometry showed that the compatibility of the modifed CNCs with organic PLA improved, which was attributed to the compatibility of the PEO chains adsorbed on the surface of the CNCs. Finally, the results of tensile tests indicated a significant improvement in terms of breaking strength and elongation at the break point.

Research on Hydrolysis and Saccharification of Corn Stover

In this paper three methods(dilute acid pretreatment, aqueous ammonia/dilute acid pretreatment and alkaline pretreatment) were used to study the hydrolysis of corn stover and characteristics of each method were compared. The results showed that the lignin removal rate was 71.8% when the corn stover was treated with a caustic soda solution containing 1.5% of NaOH, at a temperature of 75 ℃ for 90 min with an initial solid-liquid ratio of 1:8(w/v). Hydrolysis yield of the NaOH pretreated sample reached 78.5%, which was much higher than other control groups. These results are useful for evaluation of pretreatment technologies, and identification of key factors that limit cellulose hydrolysis, and can also serve as a basis for designing and screening appropriate pretreatment technologies.

Kinetic Characterization of Trichoderma reesei CL847 TR3002： An Engineered Strain Producing Highly Improved Cellulolytic Cocktail

Enzymatic hydrolysis of lignocellulose is often considered to be the major economic bottleneck of the production process of bioethanol from lignocellulose. It is generally admitted that the most efficient organism for the production ofcellulolytic enzymes is the fungus Trichoderma reesei, mostly due to its high secretion capacity. Unfortunately, this fungus secretes very low concentrations of β-glucosidase, thereby often requiring β-glucosidase supplementation for complete cellulose hydrolysis. It is especially important to have sufficient quantities of β-glucosidase in order to prevent inhibition of cellobiohydrolases by cellobiose. In order to optimize the produced cocktail, a more efficient β-glucosidase was cloned into T. reesei CL847 strain. The new strain, called CL847 TR3002, secretes the evolved β-glucosidase and was tested for cellulase production in laboratory-scale reactors. Its growth kinetics and cellulase production were characterized using fed-batch and chemostat modes under various culture conditions. The cellulase activities of the evolved strain were compared with activities of the parent strain. In addition, hydrolysis of a steam exploded wheat straw was performed at three different enzyme-loading levels （5 mg/g, 10 mg/g and 20 mg/g of dry matter） and a new kinetic model was developed.

Enhancing Biogas Production from Anaerobically Digested Wheat Straw Through Ammonia Pretreatment

Aqueous ammonia was used to pretreat wheat straw to improve biodegradability and provide nitrogen source for enhancing biogas production. Three doses of ammonia(2%, 4%, and 6%, dry matter) and three moisture contents(30%, 60%, and 80%, dry matter) were applied to pretreat wheat straw for 7 days. The pretreated wheat straws were anaerobically digested at three loading rates(50, 65, and 80 g·L-1) to produce biogas. The results indicated that the wheat straw pretreated with 80% moisture content and 4% ammonia achieved the highest methane yield of 199.7 ml·g-1(based on per unit volatile solids loaded), with shorter digestion time(T80) of 25 days at the loading rate of 65 g·L-1compared to untreated one. The main chemical compositions of wheat straw were also analyzed. The cellulose and hemicellulose contents were decomposed by 2%-20% and 26%-42%, respectively,while the lignin content was hardly removed, cold-water and hot-water extracts were increased by 4%-44%, and12%-52%, respectively, for the ammonia-pretreated wheat straws at different moisture contents. The appropriate C/N ratio and decomposition of original chemical compositions into relatively readily biodegradable substances will improve the biodegradability and biogas yield.

Improvement of Cellulose Hydrolysis Process and Cost Savings

The hydrolysis process to obtain the so-called ＂reducing sugars＂ represents the main step involved in the production of the second generation bioethanol. This product can be obtained directly from various types of green biomass, replacing the use of cereals cultivations, with obvious benefits to the environment and the economy of agricultural production. However, it is necessary to improve the hydrolysis process of the cellulose to achieve this goal. To this purpose, we applied a chemical process formerly used. The values of sugars yield were increased by about 40% with respect to the previous study. Further significant cost savings were accomplished, resulting from the recovery of the by-product, calcium sulfate, commercially known as gypsum.

Kinetic Dependences of Two-Stage Dilute Acid and Enzyme Hydrolysis of Paulownia tomentosa

The sugars potential ofPaulownia tomentosa is estimated by dilute acid pretreatment and cellulase hydrolysis. The kinetics of dilute （1%） sulfuric acid hydrolysis is studied at temperatures of 100 ℃, 120 ℃ and 130 ℃, while the kinetics of the subsequent enzyme hydrolysis is examined at a temperature of 50 ℃ and reaction time varied from 60 to 300 min using cellulase complex NS 50013 and β-glucosidase N S 50010. The reducing sugars formation is modeled as a pseudo-homogeneous first order reaction in view of the kinetics of dilute sulfuric acid hydrolysis. The results obtained indicate that the reaction proceeds in an energetically homogeneous system （E = const） providing identical accessibility of the reagent to the hydrolyzing sites （A = const）. The enzyme hydrolysis kinetics follows heterogeneous catalytic mechanism. The process is described by an exponential kinetic equation, which is well recognised in case of processes on uniformly inhomogeneous surfaces. The current rate decreases significantly probably because of exhaustion of the available active sites on the surface and steric hindrances due to the presence of lignin. This investigation provides information of importance for the fermentation step of the bio-ethanol production process.

Efficient Degradation of Cellulose in Its Homogeneously Aqueous Solution over 3D Metal-Organic Framework/Graphene Hydrogel Catalyst

Catalytic degradation of cellulose to chemicals is an attracting topic today for the conver- sion of biomass, and the development of novel catalysts is a key point. Since metal-organic frameworks （MOFs） possess uniform, continuous, and permeable channels, they are valu- able candidate as catalysts. Here, a new 3D MOF/graphene catalyst was prepared by in situ growth of the zeolitic imidazolate frameworks （ZIF-8） nanoparticles inside the pore of an as-formed 3D reduced graphene oxide （rGO） hydrogel. The ZIF-8/rGO nanocomposite owns both micropores and mesopores with large specific surface area and plenty of acids sites, which is an idea catalyst for biomass degradation. Cellulose was dissolved in allmline aqueous solution at first, and then it was degraded efficiently over the new catalyst under hydrothermal condition. The conversion reaches 100% while the main products are formic acid with a maximum yield of 93.66%. In addition, the catalyst can be reused with high activity.

Characterization of dominant and cellulolytic bacterial communities along the gut of silver carp Hypophthalmichthys molitrix during cyanobacterial blooms

Silver carp is one of the most important planktivorous fish in Chinese aquaculture and plays a significant role controlling cyanobacterial blooms. A balanced gut microbiota is crucial for growth and health of the host because of its important roles in immune defense, digestion of complex carbohydrates, and production of enterocytes. In our study, the dominant bacterial and cellulolytic bacterial （Clostridium 1, Clostridium 111, Clostridium XIVab, and Fibrobacter） communities in the contents and mucus of the silver carp gut （foregut, midgut, and hindgut） were analyzed by denaturing gradient gel electrophoresis and quantitative polymerase chain reaction （qPCR） analyses. The results revealed that the dominant and cellulolytic bacterial communities were significantly different among gut regions as well as in contents and mucus. Bacterial diversity and richness in contents and mucus increased along the gut and were higher in contents than those in local mucus. A sequence analysis of gut samples exhibited the conservative phylotypes of Proteobacteria, Actinobacteria, and Firmicutes. The gut of silver carp harbored an abundance of cellulolytic bacteria, particularly Clostridium XIVab. The foregut segment had the highest proportions of the four cellulolytic bacteria, followed by the midgut and hindgut. However, the proportions of cellulolytic species in the silver carp gut was much lower than those in the terrestrial vertebrate gastrointestinal tract. We conclude that gut bacteria could help silver carp obtain energy from cyanobacteria, which may be why silver carp can maintain high growth rates during cyanobacterial blooms.

Optimum Condition of Rice Straw Hydrolysate Detoxification with Charcoal Powder for Cellulosic Ethanol Production by Pichiastipitis TISTR 5806

In this study, the rice straw was hydrolysed by using 3.0% （w/v） H2SO4 followed by enzymatic hydrolysis. The rice straw hydrolysate obtained was treated with charcoal powder and the optimal condition of detoxification with charcoal powder was investigated. The results showed that the optimal condition for detoxification was the use of 2.5 grams of non-sterilized charcoal powder in 100 mL hydrolysate. The mixture was operated at pH 5.0, 30 ℃ and 160 rpm for 5 min. The detoxified hydrolysate was then used for ethanol production using P. stipitis TISTR 5806. The condition of the detoxified hydrolysate fermentation which gave maximum ethanol concentration of 21 g/L was at pH 5.0, 30 ℃ and 160 rpm for 72 h. Without detoxification, the P. stipitis TISTR 5806 could not however utilize the hydrolysate for ethanol production.

N-methyl-2-pyrrolidonium-based Br?nsted-Lewis acidic ionic liquids as catalysts for the hydrolysis of cellulose

We experimentally studied the catalytic performances of a series of Brrnsted-Lewis acidic N-methyl-2-pyrrolidonium metal chlorides （[Hnmp]Cl/MClx, where M=Fe, Zn, A1, or Cu） for the hydrolysis of microcrystalline cellulose （MCC） and cotton to produce reducing sugar. A variety of factors, such as temperature, time, ionic liquid （IL） species, IL dosage, and the concentra- tion of the metal chloride were investigated. [Hnmp]Cl/FeCl3 presented the best hydrolysis performance, affording a 98.8% yield of total reducing sugar from MCC （1 h, 100 ℃, 0.1 g MCC, 0.2 g acidic IL, 2.0 g [Bmim]Cl as solvent）, which is better than or comparable to results previously obtained with other -SO3H functionalized acidic ILs. The hydrolysis performances of [Hnmp]Cl/MClx were rationalized using density functional theory calculations, which indicated that interactions between the metal chlorides and the cellulose, including charge-transfer interactions are important in the hydrolysis of cellulose and degra- dation of glucose. This work shows that Bronsted-Lewis acidic ILs are potential catalysts for the hydrolysis of cellulose to produce sugar.