Advances on Cellulose Manufacture in Biphasic Reaction Media.

Cellulose is produced industrially by the kraft and sulfite processes. The evolution of these technologies in biorefineries is driven by the need to obtain greater added value through the efficient use of raw materials and energy. In this field, organosolv technologies (and within them, those using liquid phases made up of water and one partly miscible organic solvent, known as "biphasic fractionation" in reference to the number of liquid phases) represent an alternative that is receiving increasing interest. This study considers basic aspects of the composition of lignocellulosic materials, describes the fundamentals of industrial cellulose pulp production processes, introduces the organosolv methods, and comprehensively reviews published results on organosolv fractionation based on the use of media containing water and an immiscible solvent (1-butanol, 1-pentanol or 2-methyltetrahydrofuran). Special attention is devoted to aspects related to cellulose recovery and fractionation selectivity, measured through the amount and composition of the treated solids.

Stable coordination of the inhibitory Ca2+ ion at the metal ion-dependent adhesion site in integrin CD11b/CD18 by an antibody-derived ligand aspartate: implications for integrin regulation and structure-based drug design.

A central feature of integrin interaction with physiologic ligands is the monodentate binding of a ligand carboxylate to a Mg(2+) ion hexacoordinated at the metal ion-dependent adhesion site (MIDAS) in the integrin A domain. This interaction stabilizes the A domain in the high-affinity state, which is distinguished from the default low-affinity state by tertiary changes in the domain that culminate in cell adhesion. Small molecule ligand-mimetic integrin antagonists act as partial agonists, eliciting similar activating conformational changes in the A domain, which has contributed to paradoxical adhesion and increased patient mortality in large clinical trials. As with other ligand-mimetic integrin antagonists, the function-blocking mAb 107 binds MIDAS of integrin CD11b/CD18 A domain (CD11bA), but in contrast, it favors the inhibitory Ca(2+) ion over the Mg(2+) ion at MIDAS. We determined the crystal structures of the Fab fragment of mAb 107 complexed to the low- and high-affinity states of CD11bA. Favored binding of the Ca(2+) ion at MIDAS is caused by the unusual symmetric bidentate ligation of a Fab-derived ligand Asp to a heptacoordinated MIDAS Ca(2+) ion. Binding of the Fab fragment of mAb 107 to CD11bA did not trigger the activating tertiary changes in the domain or in the full-length integrin. These data show that the denticity of the ligand Asp/Glu can modify the divalent cation selectivity at MIDAS and hence integrin function. Stabilizing the Ca(2+) ion at MIDAS by bidentate ligation to a ligand Asp/Glu may provide one approach for designing pure integrin antagonists.

Technologies for Eucalyptus wood processing in the scope of biorefineries: A comprehensive review.

Eucalyptus is the most widely planted type of hardwoods, and represents an important biomass source for the production of fuels, chemicals, and materials. Its industrial benefit can be achieved by processes following the biorefinery concept, which is based on the selective separation ("fractionation") of the major components (hemicelluloses, cellulose and lignin), and on the generation of added-value from the resulting fractions. This article provides a in-depth assessment on the composition of Eucalyptus wood and a critical evaluation of selected technologies allowing its overall exploitation. These latter include treatments with organosolvents and with emerging fractionation agents (ionic liquids and deep eutectic solvents). The comparative evaluation of the diverse processing technologies is carried out in terms of degree of fractionation, yields and selectivities. The weak and strong points, challenges, and opportunities of the diverse fractionation methods are identified, focusing on the integral utilization of the feedstocks.

SSF production of lactic acid from cellulosic biosludges.

The use of cellulosic biosludges generated in a Kraft pulp mill was investigated as substrate for lactic acid production by simultaneous saccharification and fermentation (SSF). The effect of the operation mode (batch or fedbatch), the initial liquid to solid ratio (12 or 30 g/g) and the nutrient supplementation (MRS components or none) on several parameters including lactic acid concentration, volumetric productivity and product yields, were evaluated. When the operation was carried out in fedbatch mode with nutrient supplementation and using a LSR(0)=12 g/g, a broth containing 42 g/L was obtained after 48 h with a volumetric productivity of 0.87 g/L h and a product yield of 37.8 g lactic acid/100 g biosludges. In a similar experiment carried out without nutrient supplementation, a lactic acid concentration of 39.4 g/L was obtained after 48 h with a volumetric productivity of 0.82 g/L h and a product yield of 35.5 g L-lactic acid/100 g biosludges.

In vitro assessment of the prebiotic potential of Aloe vera mucilage and its impact on the human microbiota.

Aloe vera mucilage is reported to be rich in acemannan that is a polysaccharide with a backbone of ß-(1→4)-D-mannose residues acetylated at the C-2 and C-3 positions and contains some side chains of galactose and arabinose attached to the C-6 carbon. The evaluation of the prebiotic potential of Aloe vera mucilage was carried out by in vitro fermentation using intestinal microbiota from six healthy donors as the inoculum. The prebiotic activity was assessed through the quantification of short chain fatty acids (SCFA) and the evaluation of dynamic bacterial population in mixed faecal cultures by fluorescence in situ hybridization (FISH). Our findings support the possible incorporation of the Aloe vera mucilage in the development of a variety of food products known as prebiotics aimed at improving gastrointestinal health.

A biorefinery approach based on fractionation with a cheap industrial by-product for getting value from an invasive woody species.

Acacia dealbata wood (an invasive species) was subjected to fractionation with glycerol (a cheap industrial by-product), and the resulting solid phase was used as a substrate for enzymatic hydrolysis. Glycerol fractionation allowed an extensive delignification while preserving cellulose in solid phase. The solids from the fractionation stage showed high susceptibility to enzymatic hydrolysis. Solids obtained under selected fractionation conditions (glycerol content of media, 80 wt%; duration, 1h; liquid to solid ratio, 6 g/g; alkaline and neutral washing stages) were subjected to enzymatic saccharification to achieve glucose concentrations up to 85.40 g/L, with almost complete cellulose conversion into glucose. The results confirmed the potential of glycerol as a fractionation agent for biorefineries.

Topographically-patterned porous membranes in a microfluidic device as an in vitro model of renal reabsorptive barriers.

Models of reabsorptive barriers require both a means to provide realistic physiologic cues to and quantify transport across a layer of cells forming the barrier. Here we have topographically-patterned porous membranes with several user-defined pattern types. To demonstrate the utility of the patterned membranes, we selected one type of pattern and applied it to a membrane to serve as a cell culture support in a microfluidic model of a renal reabsorptive barrier. The topographic cues in the model resemble physiological cues found in vivo while the porous structure allows quantification of transport across the cell layer. Sub-micron surface topography generated via hot-embossing onto a track-etched polycarbonate membrane, fully replicated topographical features and preserved porous architecture. Pore size and shape were analyzed with SEM and image analysis to determine the effect of hot embossing on pore morphology. The membrane was assembled into a bilayer microfluidic device and a human kidney proximal tubule epithelial cell line (HK-2) and primary renal proximal tubule epithelial cells (RPTEC) were cultured to confluency on the membrane. Immunofluorescent staining of both cell types revealed protein expression indicative of the formation of a reabsorptive barrier responsive to mechanical stimulation: ZO-1 (tight junction), paxillin (focal adhesions) and acetylated α-tubulin (primary cilia). HK-2 and RPTEC aligned in the direction of ridge/groove topography of the membrane in the device, evidence that the device has mechanical control over cell response. This topographically-patterned porous membrane provides an in vitro platform on which to model reabsorptive barriers with meaningful applications for understanding biological transport phenomenon, underlying disease mechanisms, and drug toxicity.

Lesiones pulpares y periapicales en la consulta de Urgencia Estomatológica. Clínica "Felipe Soto". 2010-2011 / Periapical and pulp lesions in the stomatological emergency consultation at Felipe Soto dental clinic. 2010-2011

Introducción: la mayoría de las urgencias estomatológicas se debe a enfermedades pulpares y periapicales. En nuestro país son pocos los estudios realizados en relación con la prevalencia de estas lesiones en la población, lo que motivó la realización de este trabajo. Objetivo: determinar el comportamiento de las lesiones pulpares y periapicales en pacientes de 19 a 59 años. Material y Método: se realizó un estudio descriptivo y transversal a pacientes comprendidos entre 19 y 59 años de edad quienes asistieron a la consulta de Urgencia Estomatológica de la clínica "Felipe Soto", del municipio Boyeros, de febrero del 2010 a junio del 2011. El universo fue de 250 pacientes a los que se realizó un examen clínico-estomatológico, de los cuales solo 154 presentaron este tipo de lesiones; se analizaron variables como edad, sexo, grupo dentario y causa de la enfermedad. Resultados: el grupo dentario más afectado fue el de los molares, la caries dental fue la principal causa relacionada con la aparición de dichas patologías. Conclusiones: el sexo femenino fue el predominante y el grupo de edad más afectado fue el de 19-34 años, el grupo dentario más afectado por lesiones pulpares y periapicales fue el de los molares, seguido de las bicúspides y las principales causas relacionadas con la aparición de estas enfermedades fueron la caries dental y las obturaciones defectuosas.

Introduction: most of emergency in the Cuban stomatological clinics are due to dental pulp diseases. In our country, there are only a few studies performed on this topic in relation to the prevalence of these injuries in the population. That's why we were motivated to work on this matter. Objective: to determine pulp and periapical lesions conduct in patients from 19 to 59 years old. Material and Methods: a descriptive and cross-sectional study was done in patients between 19 and 59 years old who attended to stomatological emergency services at "Felipe Soto" clinic from Boyeros Municipality, from February 2010 to June 2011. A stomatological clinical exam was done to a population of 250 patients and the sample was of 154 patients who presented dental pulp injuries, some variables were analyzed such as age, sex, dental group and causes of the disease. Results: the more affected teeth groups were the molars. As identified causes, the dental caries were the main related to the appearance of these pathologies. Conclusions: female sex predominant and the most affected age group was the one between 19 and 34 years old. The most affected dental group due to pulp and periapical lesions was that of molars fallowed by bicuspids and the main causes related to the appearing of these sicknesses were dental caries and faulty obturations.

Aqueous pretreatment of agricultural wastes: characterization of soluble reaction products.

This work provides an assessment on the hydrothermal processing (or autohydrolysis treatments) of two lignocellulosic wastes: mixed herbs (denoted MH, mainly belonging to the Lolium species), and sunflower seed shells (denoted SS). Compositional data were obtained for both raw materials (which contained cellulose, heteroxylan and Klason lignin as major components). In autohydrolysis experiments, the raw materials presented a "susceptible fraction" which was solubilized according to a first-order kinetics. Hemicellulose degradation was followed by determination of xylooligomers, xylose and xylan substituents (arabinosyl, uronic acid and acetyl substituents). Kinetic modelling of hemicellulose degradation was carried out considering four consecutive, first-order, pseudohomogeneous reactions. The molecular weight distribution of polymeric and oligomeric fractions derived from xylan was assessed from High Performance Size Exclusion Chromatography data.

Production of D(-)-lactic acid from cellulose by simultaneous saccharification and fermentation using Lactobacillus coryniformis subsp. torquens.

D(-)-Lactic acid was produced from cellulose by simultaneous saccharification and fermentation (SSF) in media containing cellulolytic enzymes and Lactobacillus coryniformis subsp. torquens ATCC 25600 at 39 degrees C and pH 5.4, yielding 0.89 g D(-)-lactic acid g(-1) cellulose at a mean volumetric productivity of 0.5 g l(-1) h(-1). No L(+)-lactic acid was found in the medium.