Effect of Fusarium oxysporum f. sp. lycopersici on the degradation of humic acid associated with Cu, Pb, and Ni: an in vitro study |
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Authors: | Alma Rosa Corrales Escobosa Julio Alberto Landero Figueroa J Félix Gutiérrez Corona Katarzyna Wrobel and Kazimierz Wrobel |
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Institution: | (1) Department of Chemistry, University of Guanajuato, L. de Retana 5, 36000 Guanajuato, Mexico;(2) Department of Biology, University of Guanajuato, L. de Retana 5, 36000 Guanajuato, Mexico |
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Abstract: | The intent of this work was to gain further insight on the fungus-assisted degradation/solubilization of humic acid and the
related changes in metal-binding profiles. In the experimental design, Aldrich reagent humic acid (HA) or HA enriched with
Cu, Pb, and Ni (HA(Me)) was added to Fusarium oxysporum f. sp. lycopersici cultures in vitro. The cultures were supplied by different carbon- and nitrogen-containing nutrients (glucose, Glc, or glutamate,
Glu and ammonium, NH4+, or nitrate, NO3−, ions, respectively) in order to examine their possible effect on HA and HA(Me) decomposition. During the first 48 h of fungus
growth, gradual acidification to pH 2 was observed in medium containing Glc + NH4+, while for other cultures, alkalinization to pH 9 occurred and then, the above conditions were stable up to at least 200 h.
Size exclusion chromatography (SEC) with UV/Vis detection showed progressive degradation and solubilization of both HA and
HA(Me) with the increasing time of fungus growth. However, the molecular mass distributions of HA-related soluble species
were different in the presence of metals (HA(Me)) as referred to HA and were also influenced by the composition of growth
medium. The solubilization of Pb, Cu, and Ni and their association with HA molecular mass fractions were studied using inductively
coupled plasma mass spectrometry (ICP-MS) detection. Under acidic conditions, relatively high concentrations of low-molecular-mass
metallic species were found in culture supernatants, while in alkaline media, metal solubilization was generally poorer. In
contrast to low pH culture, SEC-ICP-MS results obtained in alkaline supernatants indicated metal binding to degradation products
of humic substances of MM > 5 kDa. In summary, the results of this study suggest that fungus-assisted degradation of HA and
HA(Me) might be controlled using appropriate N- and C- sources required for fungus growth, which in turn would affect molecular
mass distribution of soluble metallic species thus potentially influencing their actual bioaccessibility.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Humic acid Metals Fusarium oxysporum SEC (size exclusion chromatography) ICP-MS (inductively coupled plasma– mass spectrometry) |
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