Antimicrobial action of synthetic peptides towards wine spoilage yeasts

The antimicrobial action of selected short synthetic peptides against wine spoilage yeasts such as Cryptococcus albidus, Dekkera bruxellensis, Pichia membranifaciens, Saccharomyces cerevisiae, Zygosaccharomyces bailii and Zygosaccharomyces bisporus has been examined. Peptides analyzed include nine sequence-related antifungal hexapeptides (PAFs) previously developed by a combinatorial approach, and two representative lactoferricin B (LfcinB)-derived peptides. Different peptides had distinct activity profiles. In vitro assays identified the peptides PAF26, PAF36, and LfcinB(17-31), as having growth inhibitory properties towards several of the yeasts at low micromolar concentrations. Z. bailii and Z. bisporus were the most sensitive yeasts. In addition to their fungistatic activity, the three peptides showed fungicidal properties towards Z. bailii, Z. bisporus, and S. cerevisiae in laboratory growth medium. Remarkably, only LfcinB(17-31) against Z. bisporus had inhibitory and fungicidal properties in wine at the concentrations assayed, showing that the antimicrobial action of each peptide is dependent on both the food matrix and the target micro-organism. Lack of fungicidal activity of peptides against Z. bailii in wine is related to the presence of salt ions other than divalent cations. On the contrary, fungicidal activity of LfcinB(17-31) towards Z. bisporus was not significantly affected by wine salts. Our data identify a bioactive peptide from natural origin with potential use against the food spoilage yeast Z. bisporus, and indicate that the application of antimicrobial peptides in wine preservation deserves further investigation.     

Concentration changes of organochlorine compounds and polybromodiphenyl ethers during metamorphosis of aquatic insects

The role of insect larvae and pupae as sources of organochlorine compounds (OCs) and polybromodiphenyl ethers (PBDEs) in freshwater food webs for high predators such as fish is evaluated. Trichoptera and diptera have been taken as organisms of choice for such comparison because they are common in benthic aquatic habitats and accumulate substantial amounts of these compounds. Hexachlorobenzene, hexachlorocyclohexanes,4,4'-DDE,4,4'-DDT, polychlorobiphenyls, and PBDEs have been measured. The results show a nonselective enrichment of OCs and PBDEs from larvae to pupae. These concentration increases may result from the weight loss of pupae during metamorphosis as a consequence of mainly protein carbon respiration and lack of feeding. Despite the lack of change in total amount, the concentration increases from larvae to pupae are very relevant for the pollutant ingestion of the higher predators. The intakes of OCs and PBDEs by trout are between 2- and 5-fold higher per calorie gained when predating on pupae than on larvae. Since pollutant concentration, energy reward, predation susceptibility, and duration of life stage are very different between these two insect stages, and none of them is irrelevant for the incorporation of OCs or PBDEs to higher levels, bioaccumulation food-web models should distinguish between the two sources.     

Effect of polymer topology on the curing process and mechanical characteristics of epoxy thermosets modified with linear or multiarm star poly(ε-caprolactone)

A well-defined multiarm star copolymer, hyperbranched poly(glycidol)-b-poly(ε-caprolactone), with an average of 100-110 arms per molecule and a molecular weight of arms of 1000 g/mol (s-PCL) and a linear PCL analog (l-PCL) were used as modifiers in the curing of diglycidylether of bisphenol A (DGEBA) using ytterbium triflate as cationic initiator. The effect of the polymer topology on the curing and gelation was studied by dynamic scanning calorimetry (DSC) and rheometry. The addition of s-PCL to the resin left the complex viscosity (η∗) practically unaltered. In contrast the addition of l-PCL incremented substantially the viscosity. The addition of star-shaped modifiers decreased the shrinkage after gelation in a higher extent than the linear analog. The homogeneity of pure DGEBA and modified thermosets was proved by dynamic thermomechanical analysis (DMTA) and electronic microscopy (SEM). The addition of star-like structures led to a higher impact energy fracture in comparison to pure DGEBA and l-PCL modified thermosets and to a lower effect on the microhardness than the linear analog.     

Improvement of textured Bi1.6Pb0.4Sr2Co1.8Ox thermoelectric performances by metallic Ag additions

Bi_1.6Pb_0.4Sr₂Co_1.8O_x thermoelectric ceramics with small Ag additions (0, 1, and 3 wt%) have been successfully grown from the melt, using the laser floating zone method. Microstructure has shown a reduction in the amount of secondary phases and a better grain alignment with respect to the growth direction for an Ag content of 3 wt%. The microstructural evolution, as a function of Ag content, is confirmed with the electrical resistivity values, which show an important decrease for the 3 wt% Ag samples, leading to maximum power factor values of about 0.42 mW/K² m at 650 °C, which are among the best results obtained in this type of material.     

Dyeing behaviour of relaxed and retractile components in high-bulk yarns

The evolution of dye absorption and fine structure variations due to heat treatment in high-bulk yarns was studied. Two acrylic fibres of different commercial origin were employed. Using these, the following yarns were spun: 100% relaxed (N), 100% retractile (R), 55:45 N/R and 45:55 N/R. The evolution of fibre microstructure induced by the dyeing process was studied through the differential solubility technique in mixtures of dimethylformamide and water.     

Effectiveness of combined preservation methods to extend the shelf life of Morcilla de Burgos

Morcilla de Burgos is the most famous blood sausage in Spain. However, while producers are interested in extending its shelf life, the consumer is increasingly demanding more natural food. This situation has led to the current search for new and mild preservation technologies. Two batches of four different products: control without any treatment, control with organic acid salts (CnOAS; a 3% mixture of potassium/sodium l-lactate), control with high hydrostatic pressure processing (CnHPP; 600MPa-10min), and a combination of both treatments (OAS+HPP), were carried out to evaluate any synergistic effect that occurs when combining OAS and HPP, and the influence of different preservative treatments on the spoilage bacterial population and their evolution. HPP (with or without addition of OAS) can be considered the most suitable method for preserving morcilla de Burgos as it does not produce negative changes in sensory attributes. No clear selective effect of different treatments on the composition of the spoilage bacteria was seen and similar spoilage patterns were observed independently of the preservation treatment used.