Preparation of cellulose films from solution of bacterial cellulose in NMMO

Bacterial cellulose (BC) was dissolved in N-methylmorpholine N-oxide (NMMO) to prepare regenerated BC films (RBC) with phase inversion. The solubility of BC, supermolecule on structure, morphology, thermal and physical properties of the films were investigated by Fourier transform infrared spectroscopy (FT-IR), solid-state cross polarization/magic angle spinning ¹³C nuclear magnetic resonance (CP/MAS ¹³C NMR), wide-angle X-ray diffraction (WAXD), scanning electron microscope (SEM), and thermogravimetric analysis (TGA). The investigation suggested BC was dissolved completely in NMMO. From the C₆ signal shifts to the amorphous area, the crystallinity of materials decreased from 79.20% to 38.17%, and the transformation from cellulose I to II occurred. It was also found that the banded structure of the native materials was replaced by homogeneous and densified sections, so RBC films had better mechanical and barrier properties, and do thermal stability was similar to that of the native BC.     

Kinetic modeling of rapid enzymatic hydrolysis of crystalline cellulose after pretreatment by NMMO

Pretreatment of cellulose with an industrial cellulosic solvent, N-methylmorpholine-N-oxide, showed promising results in increasing the rate of subsequent enzymatic hydrolysis. Cotton linter was used as high crystalline cellulose. After the pretreatment, the cellulose was almost completely hydrolyzed in less than 12 h, using low enzyme loading (15 FPU/g cellulose). The pretreatment significantly decreased the total crystallinity of cellulose from 7.1 to 3.3, and drastically increased the enzyme adsorption capacity of cellulose by approximately 42 times. A semi-mechanistic model was used to describe the relationship between the cellulose concentration and the enzyme loading. In this model, two reactions for heterogeneous reaction of cellulose to glucose and cellobiose, and a homogenous reaction for cellobiose conversion to glucose was incorporated. The Langmuir model was applied to model the adsorption of cellulase onto the treated cellulose. The competitive inhibition was also considered for the effects of sugar inhibition on the rate of enzymatic hydrolysis. The kinetic parameters of the model were estimated by experimental results and evaluated.     

Dissolution of cellulose in phosphate-based ionic liquids

Two kinds of alkylimidazolium salts containing dimethyl phosphate or diethyl phosphate were obtained as room temperature ionic liquids synthesized by one step, and both of them have the ability to dissolve untreated cellulose. Especially, 1-ethyl-3-methylimidazolium diethylphosphonate ([EMIM]DEP) could obtain 4 wt% cellulose solution within 10 min under 90. The effects of dissolution temperature on cellulose dissolution time and degree of polymerization were investigated. As dissolution temperature increased, dissolution time was greatly reduced. Both the original and regenerated cellulose samples were characterized with wide-angle X-ray diffraction, thermogravimetric analysis and scanning electron micrograph. The results showed that the crystalline structure of cellulose was converted to cellulose II from cellulose I in native cellulose. It was also found that the regenerated cellulose had good thermal stability with [EMIM]DEP ionic liquid.     

The effect of heating by microwave irradiation and by conventional heating on the aldehyde concentration in aqueous glutaraldehyde solutions

Summary The effect of short time heating of aqueous solutions of glutaraldehyde (GA) on relative aldehyde concentration was determined using spectrophotometric analysis. Because free monomeric GA absorbs U. V. light at 280 nm, whereas the alpha, beta polymeric forms absorb at 235 nm, the purity of GA solutions can be expressed as the ratio: A 235 nm/A 280 nm (purification index, P.I.).Heating of 4 ml aliquots of 0.85% distilled aqueous GA solution resulted in an increase of the absorption at 280 nm which is correlated positively with temperature. No increase of absorption at 235 nm was found when solutions were kept at 40°C for several hours. The increase of absorption at 280 nm is caused by a rapid decyclization of hemiacetals producing an increase in free aldehyde concentration.No major differences in absorption were found between the solutions heated by microwave and by conventional heating. However, because microwave irradiation is known to produce an homogeneous rise in temperature, especially in bulky samples, it is expected that the results of fixation procedures will improve by the combined effect of higher temperature and enhanced diffusion rates of the fixating species.     

Degradation of hyaluronan by ultrasonication in comparison to microwave and conventional heating

Hyaluronan (hyaluronic acid, HA) was depolymerised by ultrasonication (US), microwave irradiation (MW) and conventional heating (CH), and the effect of pH and oxidants was investigated. The degradation was followed by viscometry and size exclusion chromatography coupled with low-angle light scattering. The results demonstrated that depolymerisation of HA by US leveled off to a limiting molecular mass, and the degradation was significantly enhanced by acidic and alkaline pH only in the presence of oxidants. In contrast to US, the course of depolymerisation by MW was strongly pH-dependent, and the degradation rate increased with decreasing pH. The expected enhancement of depolymerisation by MW in comparison to CH was marked only at very short heating time at pH <4. The NMR and FTIR spectral analyses indicated that HA in the whole M_w-range studied retained almost the backbone of the parent polysaccharide independently on the degradation method used. At harsh degradation conditions (long-term treatments, particularly at acidic pH or alkaline pH and in presence of oxidants) the depolymerisation was accompanied by destruction of both constituent sugar residues and formation of unsaturated structures detectable by UV-absorption at 230–240 and 260–270 nm. US-assisted oxidative degradation under mild reaction conditions was shown to be the most appropriate procedure to reduce the molecular mass of HA to 100 kDa without significant chemical modification of the polysaccharide.     

Dissolution of cellulose from AFEX-pretreated Zoysia japonica in AMIMCl with ultrasonic vibration

In this study, 1-allyl-3-methylimidazolium chloride (AMIMCl), an ionic liquid, was synthesized and characterized by a series of test methods. Pretreatment of Zoysia japonica by ammonia fiber expansion (AFEX) was shown to reduce significantly the mass of hemicellulose and lignin in biomass, thereby breaking the lignocellulosic structure. Z. japonica samples pretreated with AFEX showed reasonable solubility in AMIMCl upon ultrasonic treatment. The rate of cellulose regeneration from Z. japonica samples pretreated with AFEX increased with increase in applied power of ultrasonication within a certain power range from 0 to 110 W. The regeneration rate of cellulose from AFEX-pretreated Z. japonica reached a maximum of 97% when the ultrasonic power was 110 W. Fourier transform infrared spectroscopy and nuclear magnetic resonance analyses indicated that the regenerated cellulose was similar to microcrystalline cellulose.     

Dissolution of cellulose in ionic liquid and water mixtures as revealed by molecular dynamics simulations

Abstract

Increasing population growth and industrialization are continuously oppressing the existing energy resources, elevating the pollution and global fuel demand. Various alternate energy resources can be utilized to cope with these problems in an environment-friendly fashion. Currently, bioethanol (sugarcane, corn-derived) is one of the most widely consumed biofuels in the world. Lignocellulosic biomass is yet another attractive resource for sustainable bioethanol production. Pretreatment step plays a crucial role in the lignocellulose to bioethanol conversion by enhancing cellulose susceptibility to enzymatic hydrolysis. However, economical lignocellulose pretreatment still remains a challenging job. Ionic liquids (ILs), especially 1-ethyl-3-methylimidazolium acetate (EmimAc), is an efficient solvent for cellulose dissolution with improved enzymatic saccharification kinetics. To increase the process efficiency as well as recyclability of IL, water is shown as a compatible cosolvent for lignocellulosic pretreatment. The performance analysis of IL–water mixture based on the molecular level understanding may help to design effective pretreatment solvents. In this study, all-atom molecular dynamics simulation has been performed using EmimAc–water mixtures to understand the behavior of cellulose microcrystal containing eight glucose octamers at room and pretreatment temperatures. High-temperature simulation results show effective cellulose chain separation where cellulose–acetate interaction is found to be the driving force behind dissolution. It is also observed that pretreatment with 50 and 80% IL mixture is efficient in decreasing cellulose crystallinity. At a high IL concentration, water exists in a clustered network which gradually spans into the medium with increasing water fraction leading to loss of its cosolvation activity.

Communicated by Ramaswamy H. Sarma     

微波辐射加热对潘氏细胞染色的影响

潘氏细胞(Paneth Cell)是小肠腺的特征细胞,该细胞有合成分泌蛋白质的特点,其分泌颗粒含有防御素(defensin,又称隐窝素Chyntdin)、溶菌酶,释放后对肠道微生物有杀灭作用[1];同时亦有吞噬功能.潘氏细胞含有的分泌颗粒通常可用酸性染料如焰红(Phloxine)、伊红或橘黄G染色[2],其中以焰红染色效果最佳.     

Structure and properties of starch-based foams prepared by microwave heating from extruded pellets

The physical properties of microwave-foamed starch-based pellets, including density, porosity, cell structure, water absorption characteristics and mechanical properties were characterized. It was found that the physical properties of these starch-based foams produced by microwave heating are highly dependent on the raw materials and additives. Foam density decreased significantly after addition of 5.5–10.5% w/w salts, while foams containing nucleation agent (talc) were denser than the control with reduced cell size. A proprietary blowing agent did not affect the foam density markedly. Addition of salts also increased the water sorption of foams and plasticized cell walls. Mechanical behaviour of foamed pellets can be adjusted effectively by controlling the cell structure through using different additives. Mechanical properties of the foamed pellets in the elastic region as well as under large deformation (up to 40% strain) all follow a power–law relationship with foam density.     

Rapid Bielschowsky silver impregnation method using microwave heating

The Bielschowsky silver impregnation method has been used extensively to demonstrate neuronal processes including dendrites, axons and neurofibrils. In this study, we examined the differences in the time required for and the staining quality of the Bielschowsky method for neuronal processes when microwave heating was used instead of processing at room temperature. For this purpose, a control group of sections stained according to the conventional method at room temperature was compared to an experimental group stained in a microwave oven at 180 W for 2, 4 and 1 min in 2% silver nitrate, ammoniacal silver nitrate and gold chloride, respectively. Light microscopic examination demonstrated that the normal structure was preserved in both groups and that there was no difference in the staining quality between the control and the microwave groups. In addition, staining time for this procedure was reduced to 8 min by using the microwave oven. Our study revealed that microwave irradiation can be used safely for Bielschowsky silver impregnation of neuronal tissues.     

Rapid Bielschowsky silver impregnation method using microwave heating

The Bielschowsky silver impregnation method has been used extensively to demonstrate neuronal processes including dendrites, axons and neurofibrils. In this study, we examined the differences in the time required for and the staining quality of the Bielschowsky method for neuronal processes when microwave heating was used instead of processing at room temperature. For this purpose, a control group of sections stained according to the conventional method at room temperature was compared to an experimental group stained in a microwave oven at 180 W for 2, 4 and 1 min in 2% silver nitrate, ammoniacal silver nitrate and gold chloride, respectively. Light microscopic examination demonstrated that the normal structure was preserved in both groups and that there was no difference in the staining quality between the control and the microwave groups. In addition, staining time for this procedure was reduced to 8 min by using the microwave oven. Our study revealed that microwave irradiation can be used safely for Bielschowsky silver impregnation of neuronal tissues.     

Polymerization of 4-nitrophenylacrylate under microwave heating conditions]

The 2,2'-azodiisobutyronitrile-induced radical polymerization in solution of 4-nitrophenyl acrylate was performed under microwave heating at a frequency of 2.45 GHz. This approach allows the control of the molecular mass of poly(4-nitrophenyl acrylate) used in the synthesis of multivalent glycoconjugates. It was found that the polymerization of 4-nitrophenyl acrylate under microwave irradiation results in products with a narrower molecular mass distribution than at conventional heating.     

Characterization of pectin, flash-extracted from orange albedo by microwave heating, under pressure

Pectin was acid extracted from orange albedo by microwave heating under pressure. Extraction times ranged from 2.5 to 8 min. Solubilized pectin was characterized for molar mass (M), rms radius of gyration (Rg) and intrinsic viscosity [eta] by HPSEC with online light scattering and viscosity detection. M, Rg and [eta] all decreased with increasing extraction time. Nevertheless, at heating times of 2.5 and 3.0 min, M, Rg and [eta] were significantly higher than a commercial citrus pectin when the albedo:solvent ratio was 1:25 (w/v). At the heating time of 2.5 min Mw was 3.6 x 10(5), Rgz was 38 nm and [eta]w was 10.8 dL/g. Chromatography revealed that solubilized pectin distributions were bimodal in nature and that the low-molar-mass fraction increased at the expense of the high-molar-mass fraction with increasing extraction time. Scaling law exponents revealed that the high-molar-mass fraction was extremely compact in shape, whereas the low-molar-mass fraction was more asymmetric in shape. Possibly these results indicated that at short extraction times, pectin was solubilized as compact aggregated network structures that were broken down to their more asymmetric components with increased heating times.     

Production of bio-fuels by high temperature pyrolysis of sewage sludge using conventional and microwave heating

The pyrolysis of sewage sludge was investigated using microwave and electrical ovens as the sources of heat, and graphite and char as microwave absorbers. The main objective of this work was to maximize the gas yield and to assess its quality as a fuel and as a source of hydrogen or syngas (H2 + CO). Both gases were produced in a higher proportion by microwave pyrolysis than by conventional pyrolysis, with a maximum value of 38% for H2 and 66% for H2 + CO. The oils obtained were also characterized using FTIR and GC-MS. The use of conventional electrical heating in the pyrolysis of sewage sludge produced an oil that could have a significant environmental and toxicological impact. Conversely, microwave pyrolysis still preserved some of the functional groups of the initial sludge such as aliphatic and oxygenated compounds, whereas no heavy PACs were detected.     

Determination of fungal glucosamine using HPLC with 1-napthyl isothiocyanate derivatization and microwave heating

A rapid method for the determination of fungal glucosamine (GlcN) from Aspergillus sp BCRC 31742 was developed. The hydrochlorination process using microwave effectively reduced reaction time needed for GlcN analysis. The analytical method consisted of two steps: (1) hydrochlorination of fungal cells and (2) derivatization process. Fungal GlcN hydrochloride was reacted with 1-napthyl isothiocyanate (1-NITC) as the derivatizing agent to enhance the sensitivity of GlcN and so to achieve high resolution. This method was specific for quantification of GlcN hydrochloride at the wavelength of 230 nm. The standard deviation and relative error of the analytical results were less than 5%. By using microwave heating, the reaction time of hydrochlorination process was shortened from 24 h to 3 min. Thus, the overall time needed for analyzing GlcN from fungal sources was reduced from 5 h (thermal method) to 2 h (microwave method).     

Rapid Bielschowsky silver impregnation method using microwave heating.

The Bielschowsky silver impregnation method has been used extensively to demonstrate neuronal processes including dendrites, axons and neurofibrils. In this study, we examined the differences in the time required for and the staining quality of the Bielschowsky method for neuronal processes when microwave heating was used instead of processing at room temperature. For this purpose, a control group of sections stained according to the conventional method at room temperature was compared to an experimental group stained in a microwave oven at 180 W for 2, 4 and 1 min in 2% silver nitrate, ammoniacal silver nitrate and gold chloride, respectively. Light microscopic examination demonstrated that the normal structure was preserved in both groups and that there was no difference in the staining quality between the control and the microwave groups. In addition, staining time for this procedure was reduced to 8 min by using the microwave oven. Our study revealed that microwave irradiation can be used safely for Bielschowsky silver impregnation of neuronal tissues.     

微波加热时基托树脂收缩量的研究

目的,针对基托树脂固化的特性,探讨微波加热对树脂收缩量的影响。方法:采用四种常用基托树脂,分别采取单纯微波固化和微波加压固化聚合后,测定开盒后一周内树脂的聚合收缩情况。结果:两种固化方法收缩量均较小,适应性强。微波加压固化虽收缩量相对稍大但收缩均匀各树脂间无显著差异。结论:微波加热固化清洁高效,基托树脂结构致密,收缩量小,是今后树脂固化的一个发展方向。     

微波条件下LiCl/DMAc溶解稻秆纤维素制备还原糖

利用氯化锂/N,N-二甲基乙酰胺(LiCl/DMAc)溶剂体系在微波控制条件下对稻秆纤维素进行溶解预处理以提高纤维素酶解糖化效率。考察了微波时间和微波强度对产糖量及还原糖转化率的影响。通过扫描电镜(SEM)和热重分析仪(TG)对预处理前后稻秆纤维素的微观形貌及热稳定性进行表征,并利用高效液相色谱仪(HPLC)对酶解糖液进行糖成分鉴定和含量分析。结果表明,微波加热能够有效促进LiCl/DMAc对稻秆纤维素的溶解。与原生稻秆相比,经微波-LiCl/DMAc法溶解后再生纤维素出现明显解聚,热分解温度由290℃降至220℃。在微波功率为385 W、加热溶解时间为7 min时,所得稻秆纤维素还原糖转化率由30.90%上升至98.67%;HPLC谱图表明,糖液中主要成分为葡萄糖和木糖,分别占所得还原糖总量的43.74%和48.55%。     

Synthesis of polypeptides by microwave heating II. Function of polypeptides synthesized during repeated hydration-dehydration cycles

Summary Polypeptides, synthesized from a mixture of amino acid amides by microwave heating during repeated hydration-dehydration cycles, showed hydrolase- and oxidoreductase-like catalytic activities. Poly(GAVDH), polypeptides synthesized from an equimolar mixture (each 0.1 M) of glycinamide,l-alaninamide,l-valinamide,l-aspartic acid -amide, andl-histidinamide, catalyzed the hydrolysis of PNPAc. The hydrolytic rate of PNPAc with poly(GAVDH) was the quadruple of that ofl-histidine alone. Though the k_cat values of different resulting polypeptides were 10³–10⁶ times less than those of native hydrolases, the K_m value of the polypeptides further containing phenylalanine residues was nearly equal to that of the esterase. This result indicates the presence of hydrophobic interaction between a substrate and the polypeptides. Resulting polypeptides also showed catalytic activity for the reduction of ferricyanide ion [Fe(CN)^3–] with NADH. The polypeptides seemed to have a strong affinity for adenine nucleotides, because the reaction was inhibited by adenine derivatives such as NAD⁺ and AppA. A hypothesis for the emergence of primitive protein enzymes is discussed.