Microbial communities to mitigate contamination of PAHs in soil--possibilities and challenges: a review.

BACKGROUND, AIM, AND SCOPE: Although highly diverse and specialized prokaryotic and eukaryotic microbial communities in soil degrade polycyclic aromatic hydrocarbons (PAHs), most of these are removed slowly. This review will discuss the biotechnological possibilities to increase the microbial dissipation of PAHs from soil as well as the main biological and biotechnological challenges. DISCUSSION AND CONCLUSIONS: Microorganism provides effective and economically feasible solutions for soil cleanup and restoration. However, when the PAHs contamination is greater than the microbial ability to dissipate them, then applying genetically modified microorganisms might help to remove the contaminant. Nevertheless, it is necessary to have a more holistic review of the different individual reactions that are simultaneously taking place in a microbial cell and of the interactions microorganism-microorganism, microorganism-plant, microorganism-soil, and microorganisms-PAHs. PERSPECTIVES: Elucidating the function of genes from the PAHs-polluted soil and the study in pure cultures of isolated PAHs-degrading organisms as well as the generation of microorganisms in the laboratory that will accelerate the dissipation of PAHs and their safe application in situ have not been studied extensively. There is a latent environmental risk when genetically engineered microorganisms are used to remedy PAHs-contaminated soil.

Effect of different nitrogen sources on plant characteristics and yield of common bean (Phaseolus vulgaris L.).

Wastewater sludge can be used to fertilize crops, especially after vermicomposting (composting with earthworms to reduce pathogens). How wastewater sludge or vermicompost affects bean (Phaseolus vulgaris L.) growth is still largely unknown. In this study the effect of different forms of N fertilizer on common bean plant characteristics and yield were investigated in a Typic Fragiudepts (sandy loam) soil under greenhouse conditions. Beans were fertilized with wastewater sludge, or wastewater sludge vermicompost, or urea, or grown in unamended soil, while plant characteristics and yield were monitored (the unamended soil had no fertilization). Yields of common bean plants cultivated in unamended soil or soil amended with urea were lower than those cultivated in wastewater sludge-amended soil. Application of vermicompost further improved plant development and increased yield compared with beans cultivated in wastewater amended soil. It was found that application of organic waste products improved growth and yield of bean plants compared to those amended with inorganic fertilizer.

Emission of CO2 and N2O from soil cultivated with common bean (Phaseolus vulgaris L.) fertilized with different N sources.

Addition of different forms of nitrogen fertilizer to cultivated soil is known to affect carbon dioxide (CO(2)) and nitrous oxide (N(2)O) emissions. In this study, the effect of urea, wastewater sludge and vermicompost on emissions of CO(2) and N(2)O in soil cultivated with bean was investigated. Beans were cultivated in the greenhouse in three consecutive experiments, fertilized with or without wastewater sludge at two application rates (33 and 55 Mg fresh wastewater sludge ha(-1), i.e. 48 and 80 kg N ha(-1) considering a N mineralization rate of 40%), vermicompost derived from the wastewater sludge (212 Mg ha(-1), i.e. 80 kg N ha(-1)) or urea (170 kg ha(-1), i.e. 80 kg N ha(-1)), while pH, electrolytic conductivity (EC), inorganic nitrogen and CO(2) and N(2)O emissions were monitored. Vermicompost added to soil increased EC at onset of the experiment, but thereafter values were similar to the other treatments. Most of the NO(3)(-) was taken up by the plants, although some was leached from the upper to the lower soil layer. CO(2) emission was 375 C kg ha(-1) y(-1) in the unamended soil, 340 kg C ha(-1) y(-1) in the urea-amended soil and 839 kg ha(-1) y(-1) in the vermicompost-amended soil. N(2)O emission was 2.92 kg N ha(-1) y(-1) in soil amended with 55 Mg wastewater sludge ha(-1), but only 0.03 kg N ha(-1) y(-1) in the unamended soil. The emission of CO(2) was affected by the phenological stage of the plant while organic fertilizer increased the CO(2) and N(2)O emission, and the yield per plant. Environmental and economic implications must to be considered to decide how many, how often and what kind of organic fertilizer could be used to increase yields, while limiting soil deterioration and greenhouse gas emissions.

Revisión del papel de la fibra en nutrición infantil / Review over the role of fiber in infants and children nutrition

La fibra, es un componente importante de la alimentación humana y a pesar de ello es un concepto difícil de determinar, ya que se trata de un grupo de sustancias que sólo podemos unir por sus funciones en el intestino. El conocimiento de estas funciones ha ido mejorando en los últimos tiempos, aumentando progresivamente la importancia que le concedemos a la fibra para mantener la salud del ser humano y diferenciando los componentes de esta familia entre fibra soluble e insoluble. Uno de los problemas que plantea el estudio de la fibra de la dieta es unificar los criterios de análisis para evaluar el contenido de la misma en cada alimento. Esto se agrava debido a que el procesado de los alimentos altera en nivel de fibra e incluso enmascara su análisis.Sólo hace falta repasar los efectos de la fibra en diferentes puntos del tracto digestivo y en el metabolismo de glucosa y lípidos, para comprender su importancia en la alimentación normal y sus posibilidades terapéuticas. Pero es más difícil valorar si la ingesta real en nuestro medio, y sobre todo en niños, se adecua a las necesidades para cumplir con estas funciones. Por los datos existentes parece que el nivel de aporte es bajo y que los alimentos proveedores de la fibra están cambiando con la dieta actual. La idea, muy extendida, de que un bebé no toma fibra no es exactamente cierta y vale la pena estudiar su aporte el la lactancia materna y en la alimentación complementaria.Finalmente es necesario buscar una recomendación útil y correcta en nuestro medio para que sirva de guía en la alimentación infantil y en el intento de mejorar los hábitos (AU)