Eleven yeasts were isolated from wastewater sediment samples collected from a copper filter mine plant, located in the province of Tucumán, Argentina, and tested for their heavy metal tolerance. Two isolates were selected based on their multiple tolerance to different heavy metals and their copper biosorption capacity was studied. Analysis of the 26S rDNA D1/D2 domain sequences indicates that isolate RCL-3 showed similarity with Candida sp. and RCL-11 with Rhodotorula mucilaginosa . Growth performance and copper toxicity of both yeasts were evaluated using YNB-glucose medium supplemented with 0.1, 0.2, 0.5 and 1 mM of Cu2+ solutions. Candida sp. RCL-3 was able to grow up to 7 mg ml(-1) biomass in the presence of either 0.1 or 0.2 mM Cu2+, and at 0.5 mM Cu2+ growth reached 5.5 mg ml(-1). R. mucilaginosa RCL-11 reached 8 mg ml(-1) in the presence of 0.1 mM Cu2+, and values of 6.5 and 5.5 mg ml(-1) biomass were obtained at 0.2 and 0.5 mM Cu2+, respectively. Copper accumulation profiles were different: the metal was librated from the intact cells by Candida sp. whereas R. mucilaginosa did not show release from the cells indicating intracellular storage. Specific biosorption of copper by both isolated yeasts showed increase with the initial copper supplied with the medium (up to 11.5 and 8.0 mg Cu g(-1) biomass for Candida sp. and R. mucilaginosa , respectively). However, specific biosorption decreased with time.

No abstract

The citriculture in the international field is important not only for its nutrient and vitamin characteristics but also for its valuable source of raw materials to obtain pectin, since it was found in the internal and external parts of the citrus peel. In our country, there are several varieties of orange, from which you can obtain byproducts other than juice, such as essential oils, fertilizers, concentrates, and pectin. Pectin has different uses in the pharmaceutical industry for the preparation of suspensions, emulsions, cosmetics, capsules, etc. In the food industry, it is used as a film in packaging, thickener, and gelling agent in the manufacture of jellies and preserves, in wines as dehydrating plant tissues, in milk to precipitate casein, etc. The pectin extraction was carried out by basic or acid hydrolysis and then proceeds to purify and clarify. Once purified, the pectin was characterized in aqueous solution to determine its physicochemical properties such as molecular weight, hydrodynamic radius, hydration value, shape factor, etc. Thermal and mechanical characterizations were also performed, to assess its ability to form films.

No abstract

Twenty-one yeast-like microorganisms were isolated from tannery effluents and from a nickel-copper mine in Argentina. They were tested for their Cu(II), Ni(II), Cd(II) and Cr(VI) tolerance in qualitative assays on solid medium. Three isolates were selected for their multiple tolerance to the different heavy metals and highest tolerance to Cr(VI). According to morphological and physiological analysis and 26S rDNA D1/D2 domain sequences the isolates were characterized as: Lecythophora sp. NGV-1, Candida sp. NGV-9 and Aureobasidium pullulans VR-8. Resistance of the three strains to high Cr(VI) concentrations and their ability to remove Cr(VI) were assessed using YNB-glucose medium supplemented with 0.5 and 1 mM Cr(VI). Chromate removal activity was estimated by measuring remaining Cr(VI) concentration in the supernatant using the colorimetric 1,5-diphenylcarbazide method and total chromium was determined by flame atomic absorption spectroscopy. The results indicate that the initial Cr(VI) concentration negatively influenced growth and the specific growth rate but stimulated the metabolic activity of the three strains; resistance to Cr(VI) by these strains was mainly due to reduction of Cr(VI) rather than chromium bioaccumulation. This study showed the potential ability of these strains as tools for bioremediation of Cr(VI) from contaminated sites.

No abstract

The effect of high Cu(II) concentrations on superoxide dismutase (SOD) and catalase (CAT) activity in Candida fukuyamaensis RCL-3 and Rhodotorula mucilaginosa RCL-11, previously isolated from a copper filter at a mine plant in Argentina, was studied. Addition of 0.1, 0.2 and 0.5 mM Cu(II) to the culture medium increased total SOD and CAT activity in both strains. Native polyacrylamide gel electrophoresis revealed two bands with SOD activity for C. fukuyamaensis RCL-3 and only one for R. mucilaginosa RCL-11; the three bands corresponded to MnSOD.Intracellular accumulation of copper and morphological changes was observed using electron microscopy. Dark bodies examined with transmission electron microscopy (TEM) after 48 h of incubation probably corresponded to copper deposits. The number of dark bodies in R. mucilaginosa RCL-11 grew with increasing incubation time, whereas in C. fukuyamaensis RCL-3 the amount decreased. Scanning electron micrographs (SEM) of C. fukuyamaensis RCL-3 did not reveal any differences compared with the control, but R. mucilaginosa RCL-11 cells were bigger than control ones. TEM confirmed absence of compartmentalization mechanisms in Cu(II) detoxification since electron-dense bodies were mainly found in the cytoplasm.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.