Kinetics and mechanism of acetic acid pulping of detannined Pinus pinaster bark

Summary The observed kinetics of Pinus pinaster bark with acetic acid after alkali treatment, with or without intervening acid prehydrolysis, are satisfactorily explained by a model involving both solubilization and condensation reactions.This study was subsidised by the Xunta de Galicia. J. González is grateful to DGICYT for a research grant     

Two conifer species native to Patagonia threatened by Phytophthora austrocedri

Phytophthora austrocedri is a pathogen of Austrocedrus chilensis causing “Mal del Ciprés” (cypress sickness) in Patagonia and killing Juniperus communis in Britain, along with other species in the Cupressaceae. The evident association of the pathogen with members of the Cupressaceae makes it necessary to study the susceptibility of other species related to A. chilensis to prevent the emergence of new diseases. The present study tested the pathogenicity of P. austrocedri to three native and endemic conifers in South America: Fitzroya cupressoides, Pilgerodendron uviferum and Araucaria araucana. The results showed that F. cupressoides and P. uviferum were highly susceptible to P. austrocedri. Since these are endangered tree species, the outcome of this study is crucial for governmental agencies, policymakers and stakeholders.     

The effect of Tuber melanosporum Vitt. mycorrhization on growth, nutrition, and water relations of Quercus petraea Liebl., Quercus faginea Lamk., and Pinus halepensis Mill. seedlings

Mycorrhizal and nonmycorrhizal Quercus faginea Lamk., Quercus petraea Liebl., and Pinus halepensis Mill. one-year-old seedlings inoculated with Tuber melanosporum Vitt. have been analyzed with the purpose of studying the influence of mycorrhization on their growth, water relations, and mineral nutrition. The mycorrhization improved Q. petraea and P. halepensis seedling growth. In addition, the mycorrhization created an elastic adjustment in P. halepensis, although it did not cause any osmotic adjustment. Additionally, the mycorrhization increased phosphorus uptake in Q. faginea and P. halepensis, content of all nutrients in P. halepensis, and N content in Q. petraea.     

The Role of Iron Bacteria on Weathering and Attenuation Processes at Acidic Environments

The present research reproduces the chemical and microbiological reactions that occur naturally when a metal sulfide is discharged onto a natural soil, with special emphasis on iron cycle. The role of indigenous microbiota from an extremely acidic site on both weathering and attenuation processes related to the iron mobilization has been studied and the iron cycle has been reproduced at laboratory scale. In the first stage, the weathering phase, a residual sulfide mineral was bioleached using a mixed culture of iron-oxidizing bacteria isolated from the own substrate. The acid liquor obtained (pH 2), with a high metal concentration (160 mM in total iron), was filtered and neutralized. Solids obtained from the two sources (from the weathering process and after the neutralization stage) were characterized by X-ray and scanning electron microscope/energy dispersive X-ray spectroscopy, resulting ferric iron precipitates such as jarosites, goethites, and ferrihydrites with different crystalline properties. The contribution of ferric iron-reducing bacteria on the attenuation of high-content iron effluents was also studied. Mixed cultures of ferric iron-reducing bacteria, isolated from those acidic substrates, were active in reducing soluble ferric iron (60 mM in concentration), and a 66% of bioreduction was reached after 15 days. Dissimilatory ferric iron reduction has been achieved with adapted cultures at pH values from 7 to 4.     

Metam Sodium (MS) in Water and Cane Juice at Different Processing Conditions According to the Industrial Case. Part 1. Effects of Matrix,pH, Temperature,Processing Time,and Photolysis

The process for extracting sugarcane juice (Saccharum officinarum) represents the point of greatest contamination in sugarcane mills. Sodium dithiocarbamate also known as metam-sodium or MS is added to inhibit the growth of microorganisms especially Leuconostoc mesenteroides which is responsible for forming polysaccharides. Metam-sodium, upon decomposition, produces highly toxic byproducts. According to literature, under acidic conditions, MS is hydrolyzed resulting in methylamine (MA), CH₃NH₂, and carbon disulfide (CS₂), and in dilute alkaline solutions, MS produces an oxidation reaction characterized by the formation of elemental sulfur (S) and methyl isothiocyanate (MITC). In this paper, it was studied how MS decomposes to MITC and/or MA considering the effects of the matrix (methanol and water); of temperature (4 and 25 °C); of processing time (0, 1, 2, 3, 4 days); and of pH (4.0, 4.5, 7.0). A second experimental design considering the effects of the matrix (water and sugarcane juice); of temperature (4, 25, 35, 45 °C); of processing time (30, 300 min); and of pH (4.0, 4.5, 7.0) was derived from the results obtained considering MITC and/or MA formation. According to the statistical analysis of these results (p < 0.05), the order of the influential factors was as follows: time > matrix > pH > temperature. Results also indicated that the water matrix at pH = 4.5 and 45 °C had the lowest degradation rate (k), with a value of 8.82 day^?1, while for the sugarcane juice matrix at the same pH and temperature conditions was larger, with a k value of 30.07 day^?1. These results show that the matrix is also important for the degradation of dithiocarbamate to MITC and to MA.     

Population genetics of traditional landraces of <Emphasis Type="Italic">Cucurbita pepo</Emphasis> L., 1753 in the cloud forest in Baja Verapaz,Guatemala

Little is known regarding the effect of fragmentation and human agricultural management on the genetic variation and gene flow of Cucurbita pepo L., 1753 in moderate fragmented areas in central Guatemala. We hypothesize that the genetic variation of C. pepo is affected by forest fragmentation and by traditional agricultural management. Therefore, we aim to determine: (1) the genetic diversity and genetic structure of C. pepo in the Cloud Forest Corridor (CFC) (2) the extent of genetic admixture between commercial variety (CV) and traditional landraces (TL) of C. pepo, (3) the effect of habitat fragmentation in the population genetics of C. pepo with a landscape approach, and (4) the potential relationship between traditional management practices and genetic diversity of C. pepo in the CFC. We detected the existence of high level of genetic diversity (AR = 3.43; He = 0.50), inbreeding (Fis = 0.25) and moderate population structure of C. pepo in the CFC (Fst = 0.16). No correlation between landscape and genetics was found. Also, we found high genetic admixture between CV and TL. It seems that human practices, mainly related with seed exchange patterns, could affect genetic diversity of C. pepo in the CFC. C. pepo populations in the CFC are structured, with inbreeding, and show admixture with the CV, an aspect that could affect its genetic diversity. The agricultural management influenced the population genetics of C. pepo in the CFC, but the landscape did not. We suggest that special efforts should be made to preserve the diversity of this important indigenous food source for Guatemalan people as well as their management practices.     

Screening brassicaceous plants as biofumigants for management of Phytophthora cinnamomi oak disease

Brassicaceous plants rich in glucosinolates have been used as biofumigants for the management of soilborne pathogens. Efficacy of Brassica plant tissue has mainly been attributed to toxic isothiocyanates released upon the hydrolysis of glucosinolates. Management of Phytophthora cinnamomi, the causal agent of oak root rot in rangeland ecosystems using biofumigation, is promising, but requires further validation. The biofumigation activity of 14 brassicaceous plants was evaluated under experimental conditions. All evaluated plants rich in sinigrin suppressed (100%) the mycelial growth of P. cinnamomi, while plants rich in aromatic or other aliphatic glucosinolates had little or no suppressive effect. Simulating soil amendment in field conditions, the effects on natural soil artificially infested with P. cinnamomi chlamydospores were examined with Brassica juncea, Eruca vesicaria and Lepidium sativum, three species with different glucosinolate profiles. Only B. juncea decreased the viability of chlamydospores significantly in comparison with untreated soil only 1 day after biofumigation, whereas E. vesicaria needed 8 days to reach significance and L. sativum had no effect at all. Despite the decreases in soil inoculum, biofumigation with B. juncea did not prevent the root infections in a highly susceptible host (Lupinus luteus). However, biofumigation with plants rich in sinigrin, such as B. juncea, decreased P. cinnamomi soil inoculum under the experimental minimum threshold for oak disease expression. Although biofumigation should be considered as an effective measure to be incorporated in integrated control of the oak disease, biofumigation by itself would not be effective enough for the substantial suppression of P. cinnamomi inoculum.     

Effect of cooking temperatures on chemical changes in species of organic arsenic in seafood

The concentrations of arsenobetaine (AB), tetramethylarsonium ion (TMA(+)), and trimethylarsine oxide (TMAO) were determined in samples of sole, dory, hake, and sardine, raw and after being subjected to cooking processes--baking, frying, and grilling--at various temperatures. In all cases, the temperature attained inside the product during the cooking process was measured. The arsenic species extracted from the samples with methanol/water were separated by means of a column switching technique between a PRP-X100 column and a PRP-X200 column. AB was detected by hydride generation atomic absorption spectrometry, whereas TMA(+) and TMAO were detected by hydride generation atomic fluorescence spectrometry. The results obtained showed that, in all of the types of seafood studied, TMA(+) appeared after cooking, possibly because heating facilitates decarboxylation of AB to TMA(+).     

Bottled-Water Quality in Metropolitan Mexico City

Bacteriological and physico-chemical parameters of 265 samples from 39 brands sold in 5-gallon plastic and glass bottles and 2-5 L plastic containers were analyzed to determine the quality of bottled water distributed in Mexico City. Tests included fecal and total coliform counts, alkalinity, total hardness, chloride, calcium and magnesium concentrations, pH and conductivity. Correlation and cluster analyses and ANOVA were carried out, and a comparison made of the averages with the maximum permissible levels established in the Official Mexican Norms. Concerning the investigated parameters no differences (p > 0.05) between the brands were found. Physico-chemical parameters were studied and all the samples were within the permissible limits. Most samples taken from the 5-gallon containers exceeded the maximum bacteriological limits. It was concluded that the bacteriological quality of the brands studied was extremely variable. Appropriate sanitary measures, should be established to control this aspect.