27The study of the beneficial effects of the interaction between plants and soil microorganisms 28 towards bioremediation of contaminated soil has been studied over the past 30 years. This 29 subject has been summarized as the process where organic contaminants can be removed 30 from the soil through the interaction between roots and catabolic microbial populations. This 31 study assessed the tolerance of different plant species against polycyclic aromatic 32 hydrocarbon-non aqueous phase liquid (PAH-NAPL) contaminated soil and the feasibility of 33 the use of their root biomass to promote the biodegradation of 14 C-phenanthene. Toxicity 34 results showed that seeds germination was not affected by the presence of PAHs. 35 Furthermore, mineralisation of 14 C-phenanthrene was significantly enhanced by the addition 36 of root biomass after at least two weeks incubation. Moreover, bacterial numbers did not 37 show a significant relationship with 14 C-phenanthrene mineralisation. Results showed that the 38 higher mineralisation of 14 C-phenanthrene is not related to an increase on the microbial 39 numbers as is normally assumed. 40 41

No abstract

Plant-assisted biodegradation can offer a cost-effective and sustainable approach for the bioremediation of PAHs in soil. As such, selecting the most appropriate plant species is important. The potential for plant-assisted biodegradation of complex PAH-diesel mixtures in soil by sorghum (Sorghum bicolor) and alfalfa (Medicago sativa) grown as monocultures and mixed cultures using 14 C-contaminants has not been widely reported. The objective of this study was to assess 14 C-phenanthrene mineralisation profiles in mixtures of PAH-diesel in soil in the presence of Sorghum bicolor and Medicago sativa. Soil was spiked with PAHs and diesel, after which M. sativa and S. bicolor were introduced and grown as mono-or mixedcultures. The toxicity of the PAH-diesel oil mixture in the planted treatments, as well as its effect on the mineralisation of 14 C-phenanthrene were evaluated. Monocultures of both plant species tolerated the complex PAH-diesel mixtures based on growth and survival, and increased rates and extents of 14 C-phenanthrene mineralisation in soil. The influence of PAH concentration on 14 C-phenanthrene mineralisation profiles varied in planted and unplanted treatments. The rates and extents of 14 C-phenanthrene mineralisation tended to decrease in diesel amended soil, especially at low PAH concentrations. To the best of the authors' knowledge, this is the first report of 14 C-phenanthrene mineralisation patterns in complex PAHdiesel oil mixtures contaminated soil especially with respect to the specified plant species. The findings offer new insights on mono-and multi-species phytotoxicity as well as plant-assisted biodegradation of PAH mixtures in soil which may be useful in the risk assessment and remediation of contaminated sites.

The presence of black carbon (BC) in soil drastically reduced the mineralization of C-phenanthrene and its extractability by hydroxylpropyl-β-cyclodextrin (HPCD) extractions. This study also tested the effects of pH on the HPCD extraction of 14 C-phenanthrene in soils with BC. Extractions using 60 mM HPCD solutions prepared in deionized water (pH 5.89) and phosphate buffers (pH 7 and 8) were conducted on 14 C-phenanthrene-spiked soils amended with three different types of BC (1% dry weight) after 1, 25, and 50 d of ageing. Biodegradation assays using a Pseudomonas sp. strain were also carried out. Results showed that after 1 and 25 d, HPCD at pH 7 extracted significantly more 14 C-phenanthrene (p < 0.05) from BC-amended soils than the other two solutions (un-buffered and pH 8), while HPCD at pH 8 extracted statistically similar (p > 0.05) amounts of phenanthrene compared to the un-buffered solution. At 50 d, HPCD at pH 8 generally extracted more 14 C-phenanthrene from all treatments. It was proposed that higher pH promoted the dissolution of soil organic matter (SOM), leading to a greater solubility of phenanthrene in the solvent phase and enhancing the extractive capability of HPCD solutions. Although correlations between extractability and biodegradability of 14 C-phenanthrene in BC-amended soils were poor, increasing pH was demonstrated a viable approach to enhancing HPCD extractive capability from the 14 C-PAH from soil.

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El lactosuero es un residuo de la industria láctea, generado principalmente en la producción de queso. Este residuo representa entre el 80 y 90% del volumen de leche utilizada para la producción de queso, el cual se caracteriza por su alto contenido orgánico, con la capacidad de contaminar ríos, lagos, suelos, entre otros, cuando es desechado sin tratamiento previo, lo cual lo convierte de interés ambiental. Sin embargo, el principal problema de la mayoría de las industrias queseras, es no contar con sistemas adecuados para su gestión, en gran medida por su costoso tratamiento. Ante la situación planteada, la alta carga orgánica del lactosuero tiene potencial de ser valorizada como una fuente de carbono renovable, principalmente por su contenido de lactosa. Este disacárido puede ser tratado con Kluyveromyces marxianus, levadura con capacidad de degradar lactosa y utilizarla en la producción de diferentes productos. El presente documento, es una revisión de los bio-productos generados a partir de lactosuero utilizando la levadura Kluyveromyces marxianus, con el objetivo de proporcionar información comparativa de resultados de pre-tratamientos realizados al lactosuero, rendimiento de productos y reducción de contenido orgánico.

This study investigated the use of a hydrophobic resin, amberlite XAD, as a tool for assessing the biodegradation potential of 14 C-phenanthene in soil. The method was optimised in terms of soil/XAD ratio, shaking, extraction time and eluting solvent. The most effective method was then tested on selected XADs, and the performance compared with cyclodextrin (HP-β-CD) and dichloromethane (DCM) extractions suitability to predict phenanthrene biodegradation in soil over 100 d. Results showed that the optimum conditions for the XAD extraction technique are a 2:1 soil/XAD ratio, 100 rpm mixing for 22 h and elution using a DCM:methanol solution (1:1). Mineralisation of 14 C-phenanthrene was accurately predicted by HP-β-CD (r 2 = 0.990, slope = 0.953, intercept = 1.374) and XAD-4 extractions (r 2 = 0.989, slope = 0.820, intercept = 6.567), while DCM overestimated the bioaccessibility of 14 C-phenanthrene (r 2 = 0.999, slope = 1.328, intercept =-49.507). This investigation showed that XAD extraction can be considered a suitable non-exhaustive technique for estimating biodegradability of phenanthrene in soil.

La contaminación ocasionada por las actividades humanas representa un problema para la homeostasis ambiental. Por esta razón la necesidad de aplicar tecnologías que permitan solucionar esta problemática se ha convertido en una prioridad. En este sentido la fitorremediación se presenta como una opción viable para llevar a cabo la estabilización y extracción de uno de los contaminantes más persistentes en el suelo; los metales pesados. Así lo dejan de manifiesto varias investigaciones que han demostrado el potencial de algunas especies de plantas para tratar este tipo de contaminantes. Las especies a utilizar en fitorremediación deben contar con la capacidad de tolerar altas concentraciones de elementos como el As, Cd, Cr, Co, Mn, Ni, Pb, Se, Ta y Zn, esto al emplear eficientemente estrategias basadas en la exclusión o la acumulación. Aunque la tolerancia a estos últimos es fundamental, varios autores han señalado que existe la necesidad de utilizar especies con la capacidad de resistir los factores abióticos de los sitios a tratar, tales como un alto contenido de sales, temperaturas extremas y una baja disponibilidad de agua. Esto es importante puesto que los factores antes mencionados condicionan el crecimiento y desarrollo de las plantas al limitar la cantidad de nutrientes que son absorbidos por las raíces, inhibir la actividad fotosintética u ocasionar marchitez por deshidratación, situaciones que, dificultan la continuidad y el éxito de los procesos de fitorremediación.