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Softwood bark is an important source for producing chemicals and materials as well as bioenergy. Extraction is regarded as a key technology for obtaining chemicals in general, and valorizing bark as a source of such chemicals in particular. In this paper, properties of 237 compounds identified in various studies dealing with extraction of softwood bark were described. Finally, some challenges and perspectives on the production of chemicals from bark are discussed., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Nanomaterials based on chitosan have emerged as promising carriers of therapeutic agents for drug delivery due to good biocompatibility, biodegradability, and low toxicity. Chitosan originated nanocarriers have been prepared by mini-emulsion, chemical or ionic gelation, coacervation/precipitation, and spray-drying methods. As alternatives to these traditional fabrication methods, self-assembled chitosan nanomaterials show significant advantages and have received growing scientific attention in recent years. Self-assembly is a spontaneous process by which organized structures with particular functions and properties could be obtained without additional complicated processing or modification steps. In this review, we focus on recent progress in the design, fabrication and physicochemical aspects of chitosan-based self-assembled nanomaterials. Their applications in drug delivery of different therapeutic agents are also discussed in details., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Woody biomass is renewable only if sustainable production is imposed. An optimum and sustainable biomass stand production rate is found to be one with the incremental growth rate at harvest equal to the average overall growth rate. Utilization of woody biomass leads to a sustainable economy. Woody biomass is comprised of at least four components: extractives, hemicellulose, lignin and cellulose. While extractives and hemicellulose are least resistant to chemical and thermal degradation, cellulose is most resistant to chemical, thermal, and biological attack. The difference or heterogeneity in reactivity leads to the recalcitrance of woody biomass at conversion. A selection of processes is presented together as a biorefinery based on incremental sequential deconstruction, fractionation/conversion of woody biomass to achieve efficient separation of major components. A preference is given to a biorefinery absent of pretreatment and detoxification process that produce waste byproducts. While numerous biorefinery approaches are known, a focused review on the integrated studies of water-based biorefinery processes is presented. Hot-water extraction is the first process step to extract value from woody biomass while improving the quality of the remaining solid material. This first step removes extractives and hemicellulose fractions from woody biomass. While extractives and hemicellulose are largely removed in the extraction liquor, cellulose and lignin largely remain in the residual woody structure. Xylo-oligomers, aromatics and acetic acid in the hardwood extract are the major components having the greatest potential value for development. Higher temperature and longer residence time lead to higher mass removal. While high temperature (>200°C) can lead to nearly total dissolution, the amount of sugars present in the extraction liquor decreases rapidly with temperature. Dilute acid hydrolysis of concentrated wood extracts renders the wood extract with monomeric sugars. At higher acid concentration and higher temperature the hydrolysis produced more xylose monomers in a comparatively shorter period of reaction time. Xylose is the most abundant monomeric sugar in the hydrolysate. The other comparatively small amounts of monomeric sugars include arabinose, glucose, rhamnose, mannose and galactose. Acetic acid, formic acid, furfural, HMF and other byproducts are inevitably generated during the acid hydrolysis process. Short reaction time is preferred for the hydrolysis of hot-water wood extracts. Acid hydrolysis presents a perfect opportunity for the removal or separation of aromatic materials from the wood extract/hydrolysate. The hot-water wood extract hydrolysate, after solid-removal, can be purified by Nano-membrane filtration to yield a fermentable sugar stream. Fermentation products such as ethanol can be produced from the sugar stream without a detoxification step., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The effect of hot-water extraction on alkaline pulping was investigated. The properties of black liquor and pulp strength of bagasse were analyzed. The extraction was conducted at 160 degrees C for 30min where 13.2% of the mass was dissolved in the extraction liquor. Untreated bagasse and extracted bagasse were digested by soda and soda-AQ processes at 17% and 15.5% (with 0.1% AQ) alkali charge (NaOH). Cooking temperatures were 160 degrees C and 155 degrees C respectively. The pulp from extracted bagasse had a lower Kappa number and a higher viscosity compared to the pulp from the untreated bagasse. The black liquor from pulping extracted bagasse had a lower solid content, a lower viscosity and a lower silica content, but a higher heating value than that from pulping of untreated bagasse. Hot-water extraction resulted in a significant decrease in bleaching chemical consumption and the formation of chlorinated organics. Pulp strength properties such as the tensile index and the burst index were found to be lower, but the tear index, bulk, opacity and pulp freeness were found to be higher when hot-water extraction was applied., (Copyright 2010 Elsevier Inc. All rights reserved.)

The conversion of biomass to chemicals and energy is imperative to sustaining our way of life as known to us today. Fossil chemical and energy sources are traditionally regarded as wastes from a distant past. Petroleum, natural gas, and coal are not being regenerated in a sustainable manner. However, biomass sources such as algae, grasses, bushes and forests are continuously being replenished. Woody biomass represents the most abundant and available biomass source. Woody biomass is a reliably sustainable source of chemicals and energy that could be replenished at a rate consistent with our needs. The biorefinery is a concept describing the collection of processes used to convert biomass to chemicals and energy. Woody biomass presents more challenges than cereal grains for conversion to platform chemicals due to its stereochemical structures. Woody biomass can be thought of as comprised of at least four components: extractives, hemicellulose, lignin and cellulose. Each of these four components has a different degree of resistance to chemical, thermal and biological degradation. The biorefinery concept proposed at ESF (State University of New York - College of Environmental Science and Forestry) aims at incremental sequential deconstruction, fractionation/conversion of woody biomass to achieve efficient separation of major components. The emphasis of this work is on the kinetics of hot-water extraction, filling the gap in the fundamental understanding, linking engineering developments, and completing the first step in the biorefinery processes. This first step removes extractives and hemicellulose fractions from woody biomass. While extractives and hemicellulose are largely removed in the extraction liquor, cellulose and lignin largely remain in the residual woody structure. Xylo-oligomers and acetic acid in the extract are the major components having the greatest potential value for development. Extraction/hydrolysis involves at least 16 general reactions that could be divided into four categories: adsorption of proton onto woody biomass, hydrolysis reactions on the woody biomass surface, dissolution of soluble substances into the extraction liquor, and hydrolysis and dehydration decomposition in the extraction liquor. The extraction/hydrolysis rates are significantly simplified when the reactivity of all the intermonomer bonds are regarded as identical within each macromolecule, and the overall reactivity are identical for all the extractable macromolecules on the surface. A pseudo-first order extraction rate expression has been derived based on concentrations in monomer units. The reaction rate constant is however lower at the beginning of the extraction than that towards the end of the extraction. Furthermore, the H-factor and/or severity factor can be applied to lump the effects of temperature and residence time on the extraction process, at least for short times. This provides a means to control and optimize the performance of the extraction process effectively., (Copyright 2010 Elsevier Inc. All rights reserved.)

Microcrystalline cellulose (MCC) was pretreated with phosphoric acid at 323K for 10h. X-ray diffraction (XRD) and Atomic Force Microscope (AFM) analyses revealed that the fiber surface morphology of pretreated MCC (P-MCC) were uneven and rough with the crystalline diffraction peaks of P-MCC decreased to a distinct range. The X-ray Photoelectron Spectroscopy (XPS) analysis showed that the uneven and rough surface of P-MCC could enhance the adsorption of cellulose to the molecular surface of cellulose, which is one of the key factors affecting enzymatic hydrolysis of cellulose. A reversible first order kinetics was employed to describe the adsorption kinetics of cellulase to MCC and P-MCC, and the adsorption rate constants of MCC and P-MCC were found to be 0.016, 0.024, 0.041, and 0.095, 0.149, 0.218min(-1), respectively at 278K, 293K and 308K. The activation energies of MCC and P-MCC hydrolysis reactions were found to be 22.257 and 19.721kJ mol(-1). The major hydrolysis products of MCC and P-MCC were cellobiose and glucose. Hydrolysis of MCC for 120h resulted in yields of glucose (7.21%), cellobiose (13.16%) and total sugars (20.37%). However, after the pretreatment with phosphoric acid, the corresponding sugar yields resulted from enzymatic hydrolysis of P-MCC were increased to 24.10%, 41.42%, and 65.52%; respectively, which were 3.34, 3.15, and 3.22 times of the sugars yields from enzymatic hydrolysis of MCC., (Copyright 2010 Elsevier Inc. All rights reserved.)

Hemicellulose is a potential by-product currently under-utilized in the papermaking industry. It is a hetero-carbohydrate polymer. For hardwood hemicelluloses, D-xylose is the major component upon depolymerization. At SUNY-ESF, wood extracts were obtained by extracting sugar maple wood chips with hot water at an elevated temperature. The wood extracts were then concentrated and acid hydrolyzed. Ethanologenic bacteria, E. coli FBR5, had a good performance in pure xylose medium for ethanol production. However, FBR5 was strongly inhibited in dilute sulfuric acid hydrolyzate of hot-water wood extract. FBR5 was challenged by hot-water wood extract hydrolyzate in this study. After repeated strain adaptation, an improved strain: E. coli FBHW was obtained. Fermentation experiments indicated that FBHW was resistant to the toxicity of hydrolyzate in the fermentation media of concentrated hydrolyzate, and xylose was completely utilized by the strain to produce ethanol. FBHW was grown in the concentrated hydrolyzate without any detoxification treatment and has yielded 36.8g/L ethanol., (Copyright 2010 Elsevier Inc. All rights reserved.)

Nucleoside derivatives are a class of compounds that have attracted intense interest in biotechnology and medicine. Use of biocatalysts opens exciting opportunities for selective synthesis of many nucleoside derivatives, and such an approach offers simplicity, exquisite selectivity and environmentally benign processes. Here we reviewed current achievements in the biocatalytic transformation of nucleoside derivatives from the literature between 2000 and 2009. This article is arranged according to the types of reactions that can be employed to transform nucleoside derivatives, which include acylation, deacylation, glycosylation, halogenation and deamination., ((c) 2010 Elsevier Inc. All rights reserved.)

The conversion of biomass into chemicals and energy is essential in order to sustain our present way of life. Fossil fuels are currently the predominant energy source, but fossil deposits are limited and not renewable. Biomass is a reliable potential source of materials, chemicals and energy that can be replenished to keep pace with our needs. A biorefinery is a concept for the collection of processes used to convert biomass into materials, chemicals and energy. The biorefinery is a "catch and release" method for using carbon that is beneficial to both the environment and the economy. In this study, we discuss three elements of a wood-based biorefinery, as proposed by the SUNY College of Environmental Science and Forestry (ESF): hot-water extraction, hydrolysis, and membrane separation/concentration. Hemicelluloses are the most easily separable main component of woody biomass and thus form the bulk of the extracts obtained by hot-water extraction of woody biomass. Hot-water extraction is an important step in the processes of woody biomass and product generation, replacing alternative costly pre-treatment methods. The hydrolysis of hemicelluloses produces 5-carbon sugars (mainly xylose), 6-carbon sugars (mainly glucose and mannose), and acetic acid. The use of nano-filtration membranes is an efficient technology that can be employed to fractionate hot-water extracts and wood hydrolysate. The residual solid mass after hot-water extraction has a higher energy content and contains fewer easily degradable components. This allows for more efficient subsequent processing to convert cellulose and lignin into conventional products.

We studied the process of conversion of microcrystalline-cellulose into fermentable glucose in the formic acid reaction system using cross polarization/magic angle spinning (13)C-nuclear magnetic resonance, X-ray diffraction and Fourier transform infrared spectroscopy. The results indicated that formic acid as an active agent was able to effectively penetrate into the interior space of the cellulose molecules, thus collapsing the rigid crystalline structure and allowing hydrolysis to occur easily in the amorphous zone as well as in the crystalline zone. The microcrystalline-cellulose was hydrolyzed using formic acid and 4% hydrochloric acid under mild conditions. The effects of hydrochloric acid concentration, the ratio of solid to liquid, temperature (55-75 degrees C) and retention time (0-9 h), and the concentration of glucose were analyzed. The hydrolysis velocities of microcrystalline-cellulose were 6.14 x 10(-3) h(-1) at 55 degrees C, 2.94 x 10(-2) h(-1) at 65 degrees C, and 6.84x10(-2) h(-1) at 75 degrees C. The degradation velocities of glucose were 0.01 h(-1) at 55 degrees C, 0.14 h(-1) at 65 degrees C, 0.34 h(-1) at 75 degrees C. The activation energy of microcrystalline-cellulose hydrolysis was 105.61 kJ/mol, and the activation energy of glucose degradation was 131.37 kJ/mol.