A Review on Current Strategies for Extraction and Purification of Hyaluronic Acid

Since it is known that hyaluronic acid contributes to soft tissue growth, elasticity, and scar reduction, different strategies of producing HA have been explored in order to satisfy the current demand of HA in pharmaceutical products and formulations. The current interest deals with production via bacterial and yeast fermentation and extraction from animal sources; however, the main challenge is the right extraction technique and strategy since the original sources (e.g., fermentation broth) represent a complex system containing a number of components and solutes, which complicates the achievement of high extraction rates and purity. This review sheds light on the main pathways for the production of HA, advantages, and disadvantages, along with the current efforts in extracting and purifying this high-added-value molecule from different sources. Particular emphasis has been placed on specific case studies attempting production and successful recovery. For such works, full details are given together with their relevant outcomes.     

Ordinal and nominal classification of wind speed from synoptic pressurepatterns

Wind speed reconstruction is a challenging problem in areas (mainly wind farms) where there are not direct wind measures available. Different approaches have been applied to this reconstruction, such as measure-correlate-predict algorithms, approaches based on physical models such as reanalysis methods, or more recently, indirect measures such as pressure, and its relation to wind speed. This paper adopts the latter method, and deals with wind speed estimation in wind farms from pressure measures, but including different novelties in the problem treatment. Existing synoptic pressure-based indirect approaches for wind speed estimation are based on considering the wind speed as a continuous target variable, estimating then the corresponding wind series of continuous values. However, the exact wind speed is not always needed by wind farm managers, and a general idea of the level of speed is, in the majority of cases, enough to set functional operations for the farm (such as wind turbines stop, for example). Moreover, the accuracy of the models obtained is usually improved for the classification task, given that the problem is simplified. Thus, this paper tackles the problem of wind speed prediction from synoptic pressure patterns by considering wind speed as a discrete variable and, consequently, wind speed prediction as a classification problem, with four wind level categories: low, moderate, high or very high. Moreover, taking into account that these four different classes are associated to four values in an ordinal scale, the problem can be considered as an ordinal regression problem. The performance of several ordinal and nominal classifiers and the improvement achieved by considering the ordering information are evaluated. The results obtained in this paper present the support vector machine as the best tested classifier for this task. In addition, the use of the intrinsic ordering information of the problem is shown to significantly improve ranks with respect to nominal classification, although differences in accuracy aresmall.     

Experimental evaluation of the impact of b-learning methodologies on engineering students in Spain

The aim of this article is to highlight the importance of an active learning methodology in engineering degrees in Spain. We present the outcomes of an experimental study carried out during the academic years 2007/2008 and 2008/2009 with engineering students at the University of Salamanca (Spain). In the present research, as we have done in previous ones, we have selected a subject which is common to the four degrees under consideration: Computer Science. This study explores in greater depth the validity of experimental designs coming from educational research and the impact of innovative teaching methodologies. The hypothesis that impulses this research is formulated to ascertain that the learning level and the satisfaction of students will be higher after the implementation of new teaching methodologies (based on constructive learning, collaborative work, and blended learning resources), than in more traditional teaching contexts. The obtained results partially confirm this hypothesis. The ultimate purpose of this work is that of providing evidence that contributes to the improvement of education and teaching methods for a better performance of students in engineering.     

Total Cholesterol and Desmosterol Contents in Raw, UHT, Infant Formula Powder and Human Milks Determined by a New Fast Micro-HPLC Method

A simple, fast, sensitive, and environmental friendly micro-method is described for the determination of desmosterol and cholesterol in milk samples using isocratic normal phase high performance liquid chromatography and diode array detection. After sample micro-saponification, the chromatographic separation is achieved in 10 min, further reduced to 6 min when only cholesterol is expected to be present. The method is accurate, presenting cholesterol and desmosterol recoveries >96% and inter-day RSD lower than 3%. Quantification limits were clearly below the requirements for any milk sample, with 40 and 20 μg/100 mL for cholesterol and desmosterol, respectively. Several raw and UHT commercial milk samples, infant powder formulas, and human breast milks were analyzed, with cholesterol and desmosterol (present only in the latter) contents within reported amounts. The proposed method proved to be simple and feasible for determination of a large number of samples, requiring less solvent consumption (9–13 mL of hexane for all saponification/extraction/chromatographic steps) and simpler equipment than most ones reported, and a further possibility of partial solvent recycling due to the isocratic chromatographic mode.     

Effect of Silicon and Graphite Degeneration on High-Temperature Oxidation of Ductile Cast Irons in Open Air

Oxidation of Metals - The use of high silicon ductile irons is increasing as they offer some advantages with respect to conventional pearlitic–ferritic grades such as high elongation at...     

Complete Characterization of the O-Antigen from the LPS of Aeromonas bivalvium

Aeromonas species are found in the aquatic environment, drinking water, bottled mineral water, and different types of foods, such as meat, fish, seafood, or vegetables. Some of these species are primary or opportunistic pathogens for invertebrates and vertebrates, including humans. Among the pathogenic factors associated with these species, there are the lipopolysaccharides (LPSs). LPSs are the major components of the external leaflet of Gram-negative bacterial outer membrane. LPS is a glycoconjugate, generally composed of three portions: lipid A, core oligosaccharide, and O-specific polysaccharide or O-antigen. The latter, which may be present (smooth LPS) or not (rough LPS), is the most exposed part of the LPS and is involved in the pathogenicity by protecting infecting bacteria from serum complement killing and phagocytosis. The O-antigen is a polymer of repeating oligosaccharide units with high structural variability, particularly the terminal sugar, that confers the immunological specificity to the O-antigen. In this study, we established the structure of the O-chain repeating unit of the LPS from Aeromonas bivalvium strain 868 E^T (=CECT 7113^T = LMG 23376^T), a mesophilic bacterium isolated from cockles (Cardium sp.) and obtained from a retail market in Barcelona (Spain), whose biosynthesis core LPS cluster does not contain the waaE gene as most of Aeromonas species. After mild acid hydrolysis, the lipid A was removed by centrifugation and the obtained polysaccharide was fully characterized by chemical analysis and NMR spectroscopy. The polymer consists of a heptasaccharide repeating unit containing D-GalNAc, L-Rha, D-GlcNAc, and D-FucNAc residues.     

At line prediction of PUFA and biohydrogenation intermediates in perirenal and subcutaneous fat from cattle fed sunflower or flaxseed by near infrared spectroscopy

NIRS potential to estimate the proportion of PUFA and their biohydrogenation products in adipose tissues from cattle fed sunflower or flaxseed was tested. Immediately after skinning, perirenal and subcutaneous fat samples from 63 steers were collected, scanned intact at 37 °C and 33 °C, respectively, over a NIR spectral range from 400 to 2498 nm using benchtop equipment and then analyzed for fatty acid composition. NIRS calibrations in perirenal fat showed high predictability for total and major omega − 6 and omega − 3, conjugated linolenic acids, t,t-conjugated linoleic acids (CLA), non-CLA dienes and trans-monounsaturated fatty acids, with R² (RMSECV, %) of 0.88–0.89 (0.16–0.20), 0.89–0.91 (0.07–0.08), 0.86–0.89 (0.01–0.09), 0.82 (0.07), 0.89 (0.46) and 0.86–0.88 (0.87–1.29), respectively. NIRS predictions in subcutaneous fat were less reliable, probably due to lower fatty acid variability. The results show NIRS to be a useful technique for the early, fast and relatively inexpensive estimation of proportions of fatty acids with potential human health effects in cattle perirenal fat.     

Changes in polyphenolic content and antioxidant activity after thermal treatments of grape seed extract and grape pomace

This study was undertaken to investigate the effect of heat treatment on polyphenolic content and antioxidant activity in grape pomace (GP) and grape seed extract (GSE). GP and GSE were heat treated in a furnace or autoclaved at 100 °C for 15, 30 and 60 min. Structural modifications of the polyphenols during thermal processes were determined by HPLC–MS, and the antioxidant activity was determined by ABTS, DPPH and photochemiluminescence methods. In general, furnace thermal treatment of GSE and GP did not affect the total extractable polyphenols content, tannin content, procyanidin components and the antioxidant activity. Autoclave treatment caused an extensive hydrolysis of gallocatechin (70%), catechin (61%), epicatechin (65%), procyanidin B1 (75%) and procyanidin B2 (73%) in GSE, and an increase in gallic acid (71%), gallocatechin (100%) and epicatechin gallate (129%) in GP. Autoclave treatment did not affect the antioxidant activity of GSE or GP. It can be concluded that the effect of autoclave was more severe than furnace heat treatment modifying the phenolic profile in a different manner depending on the grape seed product used. These modifications were not related with changes in antioxidant activity.