Diversity,occurrence, and life characteristics of natural entomopathogenic nematode populations from La Rioja (Northern Spain) under different agricultural management and their relationships with soil factors

Natural entomopathogenic nematode (EPN) populations were surveyed in La Rioja (Northern Spain) during two consecutive years (2003–2005) to study their diversity, occurrence, and life characteristics under different agricultural management representing natural areas and perennial and annual crops from organic and conventional systems. Native EPN species and strains were identified using morphological and molecular characteristics. Virulence, infection cycle length and reproductive potential were assessed using Galleria mellonella larvae. The EPN occurrence was evaluated through abundance, recovery frequency, larval mortality percentage and EPN population density. EPNs were also related to selected soil physical and chemical variables as well as to some soil pollutants such as heavy metals and organochlorine pesticide residues. Only two steinernematids species were identified: Steinernema feltiae was observed throughout all seasons from natural and agricultural areas and Steinernema carpocapsae in summer and autumn of 2004 from perennial crops only. The virulence of native strains was lower than other previously isolated Spanish strain from natural areas or crop field edges. EPN abundance and recovery frequency indicated that habitat type might influence EPNs occurrence stronger than seasonality with the intensity of agricultural management inversely affecting their distribution. Moreover, clay, P₂O₅, Zn, Cu and hexachlorobenzene contents negatively correlating with EPN population density. We consider that agricultural management should be taken into account if EPNs are going to be used as biological control agents.     

Rhodamine-pink as a genetic marker for yeast populations in wine fermentation

Winemaking with selected yeasts requires simple techniques to monitor the inoculated yeast. New high-concentration rhodamine-resistant mutants and low-concentration rhodamine-pink mutants, easy to detect by replica-plate assay, were obtained from selected wine yeasts. The rhodamine-pink mutations were dominant and were located at the pdr5 locus that encodes for the Pdr5 ATP-binding cassette multidrug resistance transporter. The mutants were genetically stable but had lost the killer phenotype of the parent yeast strain. They were genetically improved by elimination of recessive growth-retarding alleles followed by crossing with selected killer wine yeasts. Several spore-clones were selected according to their must fermentation kinetics and the organoleptic quality of the wine. Some spore-clones were tested in industrial winemaking, and they were easily monitored during must fermentation using a simple color-plate assay. They accounted for >96% of the total yeasts in the must, and the resulting wine had as good a quality as those made with standard commercial wine yeasts. The rhodamine-pink yeasts may also be detected by direct seeding onto rhodamine agar or by observation under fluorescence microscopy. These possibilities greatly reduce the time of analysis and make the monitoring procedure for rhodamine-pink yeasts faster, easier, and cheaper than for the genetically marked wine yeasts obtained previously.     

Chemical composition of abaca (Musa textilis) leaf fibers used for manufacturing of high quality paper pulps

The chemical composition of leaf fibers of abaca (Musa textilis), which are commonly used for high-quality paper pulp production, was thoroughly studied. The results revealed that the lignin content was 13.2% of the total fiber. The analysis of abaca fibers by pyrolysis coupled to gas chromatography-mass spectrometry (Py-GC/MS) released predominantly compounds arising from lignin and p-hydroxycinnamic acids, with high amounts of 4-vinylphenol. The latter compound was demonstrated to arise from p-coumaric acid by pyrolysis of abaca fibers in the presence of tetramethylammonium hydroxide, which released high amounts of p-coumaric acid (as the methyl derivative). Products from p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) propanoid units, with a predominance of the latter (H:G:S molar ratio of 1.5:1:4.9), were also released after Py-GC/MS of abaca fibers. Sinapyl and coniferyl acetates, which are thought to be lignin monomer precursors, were also found in abaca. The extractives content of the abaca fiber (0.4%) was low, and the most predominant compounds were free sterols (24% of total extract) and fatty acids (24% of total extract). Additionally, significant amounts of steroid ketones (10%), triglycerides (6%), omega-hydroxyfatty acids (6%), monoglycerides (4%), fatty alcohols (4%), and a series of p-hydroxycinnamyl (p-coumaric and ferulic acids) esterified with long chain alcohols and omega-hydroxyfatty acids were also found, together with minor amounts of steroid hydrocarbons, diglycerides, alpha-hydroxyfatty acids, sterol esters, and sterol glycosides.     

Effect of Extrusion Conditions and the Optimization of Phenolic Compound Content and Antioxidant Activity of Wheat Bran Using Response Surface Methodology

The extrusion process (EP) consists of heat and mechanical treatments under different conditions of moisture, shear, and pressure and rapidly causes structural alterations and changes in the functional properties of the extruded material. The aim of this study was to evaluate the effect of extrusion conditions and optimize the wheat bran extrusion conditions to achieve the greatest content of phenolic compounds and antioxidant activity using response surface methodology. The EP factors evaluated were feed moisture (FM) (25–33.54%) and final extrusion temperature (T) (140–180 °C). The properties evaluated in the extruded material were bound total phenol content (BTPC), total phenolic compounds and antioxidant activity (AOX). Analysis of variance (ANOVA) and response surface methodology were used in the evaluation. The determination coefficients, (FM)² and (T)², very significantly affected the BTPC and bound 2,2-diphenyl-1-picrylhydrazyl content (BDPPHC). The optimization was performed by overlaying two contour plots to predict the best combination regions. The optimized extrusion conditions were the following: FM?=?30% and T?=?140 °C, which provided BTPC?=?3547.01 μgGAE/g (predicted: 3589.3 μgGAE/g) and BDPPHC?=?9.5 μmolTE/g (predicted: 10.4 μmolTE/g); and FM?=?30% and T?=?180 °C, which provided BTPC?=?3342.3 μgGAE/g (predicted: 3727.7 μgGAE/g) and BDPPHC?=?9.5 μmolTE/g (predicted: 9.3 μmolTE/g). The EP increased the phenolic compounds and AOX, and enhancement of these properties in wheat bran products could make them functional foods.