Kinetics of enzymatic hydrolysis of polysaccharide-rich particulates

Both pH and volatile fatty acid (VFA) inhibit the hydrolysis of particulate organic waste. It is not clear yet whether VFA or pH is the dominant factor in hydrolysis inhibition. The effects of pH and acetate on the enzymatic hydrolysis of potato samples containing mainly carbohydrate were studied at fixed pH values (5–9) and with/without 20 g L⁻¹ acetate. The leaching liquors were refreshed at prescribed intervals. Experimental results showed that both pH and acetate influenced the hydrolysis of carbohydrate, but that pH was more influential than acetate.     

木质素磺酸镁对不同纤维素原料酶解的影响机制

为探讨木质素磺酸镁作为辅助添加剂在纤维原料酶解过程的作用机制,以两种木质素磺酸镁为研究对象,考察了不同来源木质素磺酸镁组构差异及其在不同纤维原料酶解过程中的作用。研究发现,商品木质素磺酸镁较自制木质素磺酸镁具有更高的磺化度,但自制木质素磺酸镁具有更高总羟基相对含量。商品木质素磺酸镁和自制木质素磺酸镁对微晶纤维素酶解均有促进作用;对于木质纤维原料酶解,两种木质素磺酸镁对水热法预处理物料均有抑制作用。对亚硫酸氢镁预处理物料酶解,仅低浓度的自制木质素磺酸镁表现出促进作用。该研究为解释木质素磺酸镁对纤维素原料酶解的影响机制提供了理论依据。     

Cellulosic materials: Structure and enzymatic hydrolysis relationships

Structural and morphological features of four different cellulosic materials have been deeped by X-ray, CP–MAS NMR, water retention, and specific surface area analysis. Hydrolysis time courses of two of these celluloses were followed by employing an enzymatic system consisting of a cellulase from Trichoderma viride and a cellobiase from Aspergillus niger. Experimental results were rationalized on the basis of a methematical model previously verified on the other two substrates. All the celluloses presented the same mechanistic framework involving product inhibitions. The most efficient pretreatment was found to be the dissolution of cellulosic material in the dimethyl sulfoxide–paraformaldehyde system and regeneration with ammonia. This treatment cancelled the memory of the initial structural order.     

Enzymatic hydrolysis of lignocellulosic materials in aqueous media and the subsequent microbiological synthesis of bioethanol

The enzymatic hydrolysis of lignocellulosic materials (LCMs) from miscanthus and oat husks (OH) in an aqueous medium and the subsequent production of ethanol are studied. LCMs are obtained at a pilot plant of the Institute of Problems of Chemical and Energy Technologies by means of one-stage nitric acid treatment. Enzymatic hydrolysis is conducted in an aqueous medium with a high initial concentration of phosphates (90 g/L) using freely available CelloLux-A and BrewZyme BGX industrial enzymatic preparations. The yields of reducing compounds are found to be 65.4 and 73.3% for miscanthus and oat husk LCM, respectively. The composition of monosaccharides (products of enzymatic LCM destruction) is studied for the first time. It is shown that glucose comprises the largest share of monosaccharides. Ethanol is produced from LCM for the first time. Ethanol yields per metric ton of raw material are 19.4 and 16.2 daL/t for miscanthus biomass and OH, respectively. Ethanol samples are characterized by low methanol contents (0.002 to 0.005 vol %).     

Dilute acid hydrolysis of lignocellulosic biomass

The overall aim of this work was to establish the optimum conditions for acid hydrolysis of hemicellulosic biomass in the form of potato peel. The hydrolysis reaction was undertaken in a 1l high pressure pilot batch reactor using dilute phosphoric acid. Analysis of the decomposition rate of hemicellulosic biomass (namely Cellulose, Hemicellulose and lignin) was undertaken using HPLC of the reaction products namely, 5 and 6 carbon sugars. Process parameters investigated included, reactor temperature (from 135 °C to 200 °C) and acid concentration (from 2.5% (w/w) to 10% (w/w)). Analysis of the reactor products indicated that high conversion of cellulose to glucose was apparent although arabinose conversion was quite low due to thermally un-stability. However, an overall sugar yield is 82.5% was achieved under optimum conditions. This optimum yield was obtained at 135 °C and 10% (w/w) acid concentration. 55.2 g sugar/100 g dry potato peel is produced after a time of 8 min. The work indicates that the use of potato peel may be a feasible option as a feed material for the production of sugars for biofuel synthesis, due its low cost and high sugar yields.     

Kinetics and rate of enzymatic hydrolysis of cellulose in supercritical carbon dioxide

Experiments were carried out on the application of supercritical fluid to the hydrolysis of cellulose by the enzyme, cellulase. The stability of cellulase was sustained at the pressures of up to 160 atm for 90 min at 50 ‡C in supercritical carbon dioxide. In the hydrolysis of cellulose the glucose yield was 100% at supercritical condition. Kinetic constants of hydrolysis at supercritical condition were increased as compared to those at atmospheric condition. The hydrolysis reaction was found competitively inhibited by glucose at supercritical condition.     

Adhesive bond strength development evaluation using ABES in different lignocellulosic materials

This paper presents a new application of Automated Bonding Evaluation System (ABES) for studying the reactivity of adhesive–substrate combinations (adhesive–cork, impregnated paper–wood and laminate–wood); a new sample configuration and a new kinetic model are proposed. Isothermal bond strength development was plotted as a function of time for several platen temperatures and the kinetic parameters were computed from these plot families, for each type of adhesive and combinations. The methodology developed showed to have potential in quantitative screening of adhesives and operating conditions in industrial context (production of cork composites, melamine faced boards and high pressure laminates).     

木质纤维原料的热化学液化

用热化学方法 ,可以将木质纤维原料液化成为烃、醇、酚、羧酸等多种有机物以及一些无机物。在所有的木质纤维原料液化手段中 ,热化学液化是最容易实现、同时又最经济的方法。综述了木质纤维原料热化学液化反应机理及实现木质纤维原料液化的工艺进展。将木质纤维原料转化成液体燃料或化工原料 ,对充分利用自然界中可再生资源 ,降低燃烧石油造成的环境污染 ,具有重要的意义     

Progress in the hydrolysis of lignocellulosic biomass for fuel-thanol production

以木质纤维素生产燃料乙醇具有原料可再生性和环境友好的优点而备受重视。本文介绍了国内外木质纤维素制取燃料乙醇中的水解工艺过程,包括浓酸水解、稀酸水解和酶水解工艺,分析了各工艺的技术特点,同时指出稀酸预处理-酶水解工艺将成为近几年国内外研究和开发的重点。     

木质纤维素水解制取燃料乙醇研究进展

以木质纤维素生产燃料乙醇具有原料可再生性和环境友好的优点而备受重视.本文介绍了国内外木质纤维素制取燃料乙醇中的水解工艺过程,包括浓酸水解、稀酸水解和酶水解工艺,分析了各工艺的技术特点,同时指出稀酸预处理-酶水解工艺将成为近几年国内外研究和开发的重点.     

Studies on the enzymatic hydrolysis of dextran

Summary The enzymatic hydrolysis of well-defined dextran fractions is studied. The results show that the rate constants of degradation are proportional to the molecular weight for molecular weights higher than 5000; for lower molecular weights the rate constants decrease gradually. Enzymatic hydrolysis of dextran is not a statistical reaction, since the individual rate constants of bond cleavage increase from the midpoint of the chain towards both ends. The results are discussed in comparison with acid hydrolysis of dextran, and the characteristic differences between both reactions are pointed out.     

ESCA analysis of partially converted lignocellulosic materials

Further ESCA data of the solid residues obtained by supercritical extraction of Populus tremuloides are reported. The changes of the ESCA spectra with the severity of grinding are discussed. These data allow us to draw precise conclusions on the spatial distribution of carbonaceous recondensed material as thermal conversion proceeds. The C_1s peaks are of special interest as the distribution of the four components in these peaks bears information on the nature of the chemical compounds present on the surface of the sample.     

Dropwise condensation of different steam-air mixtures on various substrate materials

Dropwise condensation of different steam-air mixtures on three substrate materials (copper, aluminium and nickel) is studied. For each steam-air mixture, the heat flux, the heat transfer coefficient and the surface temperature are observed to be highest on copper and lowest on nickel substrates for the same identical test conditions. The above heat transfer variables are related to the bulk properties of the substrate. It is concluded that the presence of non-condensable gases is an inhibiting influence on the heat transfer performance in the condensation of steam. The normalized variables \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{h_i \left(\eta \right)}}{{h_i \left(o \right)}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{T_{si} \left(\eta \right)}}{{T_{si} \left(o \right)}} $\end{document} are found to be functions of the air concentration only.     

Features of the enzymatic hydrolysis of castor oil

Ricinoleic acid, which is used in medicine and veterinary science and is the initial material in the organic synthesis of various valuable products, is obtained via the hydrolysis of castor oil. The enzymatic hydrolysis of castor oil, which allows us to conduct the process under mild conditions (in the temperature range of 35–45°C and without high pressures) is a promising method for obtaining ricinoleic acid. This work demonstrates the feasibility of the enzymatic hydrolysis of castor oil with lipase from Candida rugosa in oil-water systems without an emulsifier. We propose a method for hydrolysis without emulsifiers, simplifying the process of isolating the target product (a mixture of free fatty acids in which ricinoleic acid predominates) and thus the relevant technology. The catalyst that we use ensures the environmental friendliness of the process. Our selection of the experimental conditions for hydrolysis resulted in a 47% yield of fatty acids.     

丙二烯基二氯氧膦水解反应及宏观动力学

提出了反应步骤,通过实验确定了丙二烯基二氯氧膦水解反应控制机制,采用积分反应器研究了水解反应动力学行为,确定了独立反应数及独立反应,建立了幂函数型动力学模型,经过数学变换,利用MATLAB软件中的regress函数程序进行了参数估计和F统计检验,验证了其合理性,获得了丙二烯基二氯氧膦水解宏观动力学模型。     

木质纤维素生产燃料乙醇的研究现状

介绍了近年来国内外木质纤维素生产燃料乙醇的技术现状。评述了纤维素原料生产乙醇的预处理及水解为葡萄糖和发酵成酒精的各生产工艺。分析了各工艺的技术特点和经济性。提出应进一步加强纤维素生产燃料乙醇的研究。     

不同预处理方法对玉米秸秆吐温-80/酶水解的影响

比较了稀硫酸、氢氧化钠、氨水和氢氧化钙4种预处理方法对玉米秸秆吐温-80/酶水解的影响,结果表明:氢氧化钠预处理方法效果最佳,得到的总还原糖产率比未处理时提高了10.7倍.其红外光谱和广角X-谢线衍射谱图表明:经氢氧化钠预处理后,玉米秸秆中的木质素含量降低了62%,纤维素的结晶度也有所降低.     

Use of ionic liquids for the efficient utilization of lignocellulosic materials

Lignocellulosic materials are the most abundant renewable resource in the world and their efficient utilization provides a practical route to maintain social sustainable development. Application of ionic liquids has opened new avenues for the efficient utilization of lignocellulosic materials in such areas as fractionation, preparation of cellulose composites and derivatives, analysis, and removal of pollutants. However, there are still many challenges in putting these potential applications into practical use, for example, the high price of ionic liquids and lack of basic physico‐chemical and toxicological data. Further research and financial support are required to address such challenges. Copyright © 2008 Society of Chemical Industry