1,720,957 research outputs found
Fungal laccases degradation of endocrine disrupting compounds
Full text linkOver the past decades, water pollution by trace organic compounds (ng/L) has become one of the key environmental issues in developed countries. This is the case of the emerging contaminants called endocrine disrupting compounds (EDCs). EDCs are a new class of environmental pollutants able to mimic or antagonize the effects of endogenous hormones, and are recently drawing scientific and public attention. Their widespread presence in the environment solicits the need of their removal from the contaminated sites. One promising approach to face this challenge consists in the use of enzymatic systems able to react with these molecules. Among the possible enzymes, oxidative enzymes are attracting increasing attention because of their versatility, the possibility to produce them on large scale, and to modify their properties. In this study five different EDCs were treated with four different fungal laccases, also in the presence of both synthetic and natural mediators. Mediators significantly increased the efficiency of the enzymatic treatment, promoting the degradation of substrates recalcitrant to laccase oxidation. The laccase showing the best performances was chosen to further investigate its oxidative capabilities against micropollutant mixtures. Improvement of enzyme performances in nonylphenol degradation rate was achieved through immobilization on glass beads
Exploitation of Trametes versicolor for bioremediation of endocrine disrupting chemicals in bioreactors
No full textEndocrine disrupting chemicals (EDCs) are environmental contaminants causing increasing concerns due to their toxicity, persistence and ubiquity. In the present study, degradative capabilities of Trametes versicolor, Pleurotus ostreatus and Phanerochaete chrysosporium to act on five EDCs, which represent different classes of chemicals (phenols, parabens and phthalate) and were first applied as single compounds, were assessed. T. versicolor was selected due to its efficiency against target EDCs and its potentialities were exploited against a mixture of EDCs in a cost-effective bioremediation process. A fed-batch approach as well as a starvation strategy were applied in order to reduce the need for input of 'fresh' biomass, and avoid the requirement for external nutrients. The fungus was successfully operated in two different bioreactors over one week. Semi-batch cultures were carried out by daily adding a mixture of EDCs to the bioreactors in a total of five consecutive degradation cycles. T. versicolor was able to efficiently remove all compounds during each cycle converting up to 21 mg L-1 day-1 of the tested EDCs. The maintained ability of T. versicolor to remove EDCs without any additional nutrients represents the main outcome of this study, which enables to forecast its application in a water treatment process
Fungal laccases: versatile tools for lignocellulose transformation
No full textConversion of lignocellulosic materials to useful, high value products normally requires a pre-treatment step to transform or deconstruct the recalcitrant and heterogeneous lignin fraction. The development of ‘‘green tools’’ for the transformation of lignocellulosic feedstocks is in high demand for a sustainable exploitation of such resources. This multifaceted challenge is being addressed by an ever-increasing suite of ligninolytic enzymes isolated from various sources. Among these, fungal laccases are known to play an
important role in lignin degradation/modification processes. The white-rot fungus Pleurotus ostreatus expresses multiple laccase genes encoding isoenzymes with different properties. The availability of established recombinant expression systems for P. ostreatus laccase isoenzymes has allowed to further enrich the panel of P. ostreatus laccases by the construction of mutated, ‘‘better performing’’ enzymes through molecular evolution techniques. New oxidative catalysts with improved activity and stability either at high
temperature and at acidic and alkaline pH have been isolated and characterized
DEVELOPMENT OF BIOSYSTEMS FOR THE DETECTION AND DEGRADATION OF ENDOCRINE DISRUPTING CHEMICALS (EDCs)
No full textIn recent years, a large number of materials and compounds have been produced without adequate knowledge on their interaction with the environment and of their influence on human health. This resulted in a continuous pollution by a wide array of hazardous chemicals with different structures and toxicity levels. These chemicals have deleterious effects on the reproductive systems of various animals, including humans. This dangerous situation has required the formulation of strict environmental regulations in order to reduce the emissions and to ban the production of the incriminated compounds.
Furthermore, the development of news efficient and cost-effective technologies became necessary to resolve the problems of effluents treatment. To this aim physical and chemical processing were initially tested, but they resulted expensive and may generate a large volume of sludge.
In the last years, biological wastewater treatments have represented an attractive alternative as they could be cost-effective and environmentally friendly. For these reasons, many biodegradation processes were encouraged to resolve this problem.
In this context, the present research explores various methods for biodegradation of a class of above-mentioned chemicals: endocrine disrupting chemicals (EDCs). EDCs are able to interfere with endocrine function in a number of wildlife species, leading to adverse effects particularly in relation to reproduction.
Two kinds of processes have been specifically analysed:
• oxidation of these compounds using laccase enzymes from the white-rot fungus Pleurotus ostreatus;
• biodegradation process based on the use of different mushrooms.
As regard as laccases, their degradability performances, against each EDC, were studied in the presence and in the absence of mediators. Two different mediators were chosen, a natural and synthetic one. Mediator addition enhanced laccase activity, favouring oxidation of recalcitrant xenobiotics. Degradation capabilities of best enzyme were also studied against EDCs mixture. In order to increase oxidative capabilities of selected enzyme, its immobilization on glass beads was performed.
As concern as various mushrooms, white-rot and aquatic fungi were chosen to analyse their degradative capabilities towards each xenobiotic. Moreover, to mimic real condition, their capabilities were studied also in the presence of EDCs mixture.
In the end, considering the great amount of these micropollutants in the environment, a screening of mushrooms able to growth on EDCs was performed using ground sample
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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