1,720,960 research outputs found
Covalent immobilization of chloroperoxidase on silica gel and properties of the immobilized biocatalyst
No full textImmobilization of chloroperoxidase (CPO) isolated from the mold Caldariomyces fumago on silica gel was performed. The support was derivatized with 3-glycidoxypropyltrimethoxysilane by using a reported method and the enzyme was covalently bound via reaction with epoxide groups under mild conditions. The enzyme was still active after the immobilization process. No leaching of the enzyme from the support was detectable after repeated washings. The halogenation reaction catalysed by the immobilized enzyme in buffer was compared to that catalysed by the free enzyme. The immobilization of CPO enhanced the stability of the enzyme with respect to the effect of pH and oxidizing agent concentration
Photocatalytic treatment of industrial wastewaters using structured photocatalysts
No full textNowadays one of the most significant environmental problems is related to wastewater treatment because the release of pollutants into the environment has posed a risk to natural ecosystems and human health. Therefore, it is necessary to treat wastewater in appropriately way. Three main steps are applied in wastewater treatments that are commonly called preliminary, secondary and tertiary treatment. The preliminary and secondary treatment steps are based on physical and chemical processes. However, in most cases these types of processes are not enough alone. Among tertiary process treatment, compared to the common processes used for wastewater disinfection, new methods without the formation of disinfection byproducts have been recently investigated by researchers. In this sense, among advanced oxidation process (AOPs), heterogeneous photocatalysis is a powerful alternative technique to treat polluted water because it is able to mineralize many organic compounds through the generation of hydroxyl radicals thanks to the presence of a semiconductor activated by a light source. For engineering applications, the immobilization of catalyst powders onto a suitable solid inert support is required. In this work, ZnO immobilized on macroscopic polystyrene pellets has been prepared, characterized and studied in the photocatalytic treatment of four wastewaters samples coming from secondary and tertiary processes of wastewater treatment plant by leather industries. The efficiency of the system has been determined by measuring chemical oxygen demand (COD) and total organic carbon (TOC). Photocatalytic results showed in all cases a significant COD and TOC reduction, after 7 h of UV light irradiation
Covalent immobilization of Chloroperoxidase on silica gel: activity and stability of the new biocatalyst
No full textProcessing and characterization of innovative thermoplastic materials from wastes of the leather industry
No full textIn recent years, the development of partially or totally biodegradable materials based on natural biopolymer (such as polysaccharides, proteins of vegetal and animal origin) in combination with synthetic thermoplastic polymers, has been the subject of considerable research effort. Hydrolyzed collagen from leather industry is a natural polymer easily available at low cost and its use is not in competition with food industries or other main applications because it is a waste material and a by-product of the tanning process.
Polyethylene-collagen hydrolizate blends, at ratios of 100/0, 90/10 and 80/20, were processed using a blow film line equipped with a single screw extruder. Film blowing is a shaping technique used extensively to produce most plastics films and bags for packaging applications. The effect of processing parameters on the physical properties of blown films was investigated. The extruded films were characterized through mechanical testing, scanning electron microscopy, infrared spectroscopy and thermal analysis. The manufactured films showed satisfactory mechanical and thermal properties, thus polyethylene-collagen hydrolizate blends appears as promising candidate for the production of innovative material suitable for production of thermoplastic items for applications in packaging and agricultural segments
Inactivation studies on native and silicagel non-homogeneous immobilized chloroperoxidase
No full textA pH stability analysis was made, in the presence of tert-butyl hydroperoxide, of both immobilized and native chloroperoxidase obtained from Caldariomyces fumago and the inactivation constants (j1) evaluated. The native enzyme displays a uni-exponential decay, whereas for the immobilized enzyme a three exponential equation describes the time dependent enzyme inactivation.
For immobilized enzyme, three-exponential equation describes the enzyme time-course inactivation. The obtained inactivation constants (j3 and K3) showed an increase in the stability of a fraction of the immobilized enzyme. This is probably due to a decrease of the affinity of the enzyme
for the oxidant and not to a decrease in j3 values
Kinetic and stability studies on the chloroperoxidase complexes in presence of tert-butyl hydroperoxide
No full textThe inactivation of native chloroperoxidase (CPO) from Caldariomyces fumago in the presence of tert-butyl hydroperoxide (tert-BuOOH) was investigated. A kinetic analysis was made and the inactivation constants (V3 and K3) were evaluated. In prolonged times, uniexponential equation describes the enzyme time course inactivation. A method based on the rate of inactivation of the enzyme in the presence of the inactivating molecule tert-BuOOH was also performed. A second group of inactivation constants ( j3 and K) was obtained, which is sufficiently close to the first two, thus verifying that the decreasing of enzyme absorbance corresponds to the decay of activity
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
- …
