Abstract The contamination of soils by hydrocarbons is a serious environmental problem both due to the persistence of this pollution and by its effects on even the most pristine areas of the planet. Hydrocarbon decontamination techniques entail a high cost, imply in many cases their off-site treatment, and entail environmental risks. In contrast, the use of microbiological techniques through the addition of microbial consortia with the capacity to degrade these contaminants, are alternatives for soil biorecovery that are gathering growing interest in the construction of biopiles or ecopiles. However, for an effective application of these biotechnological techniques, it is necessary to guarantee an effectiveness in the action of these microbial consortia, whose persistence in soil is generally low. In this work, the stabilization of a microbial consortium specialized in the degradation of hydrocarbons and isolated from the own soil, has been studied through its immobilization on two classes biochars obtained form apricot stones at pyrolysis temperatures of 450° and 650°C, respectively, as well as the increase of its efficiency rate through the addition of rhamnolipids. The introduced microbial consortium achieved a degradation of 17% of the highest molecular weight hydrocarbons, an efficiency that was increased with the application of biochar and rhamnolipids up to 25% of their initial content.

Resumen La contaminación de suelos por hidrocarburos es un grave problema ambiental tanto por su persistencia como por su afección hasta las zonas más prístinas del planeta. Las técnicas de descontaminación de hidrocarburos suponen un elevado coste, implican en muchos de los casos su tratamiento exsitu y conllevan también riesgos ambientales. En contraposición, el empleo de técnicas microbiológicas mediante la adición de consorcios microbianos con capacidad para degradar estos contaminantes, son alternativas de biorrecuperación de suelos, que mediante la construcción de biopilas o ecopilas están reuniendo un creciente interés. Sin embargo, para una eficaz aplicación de estas técnicas biotecnológicas, es necesario garantizar una efectividad en la acción de estos consorcios microbianos, cuya persistencia en el suelo es generalmente baja. En este trabajo se ha buscado la estabilización de un consorcio microbiano especializado en la degradación de hidrocarburos y aislado del propio suelo contaminado, mediante su inmovilización sobre dos tipos de biochars obtenidos a partir de huesos de albaricoque con temperaturas de pirólisis de 450° y 650°C, respectivamente, así como el incremento de su eficacia mediante la adición de ramnolípidos. El consorcio microbiano introducido consiguió una tasa de degradación del 17% de los hidrocarburos de mayor peso molecular, eficiencia que se incrementó con la aplicación de biochar o ramnolípidos hasta el 25% de su contenido inicial.

Abstract Senescence-associated proteolysis in plants is a complex and controlled process, essential for mobilization of nutrients from old or stressed tissues, mainly leaves, to growing or sink organs. Protein breakdown in senescing leaves involves many plastidial and nuclear proteases, regulators, different subcellular locations and dynamic protein traffic to ensure the complete transformation of proteins of high molecular weight into transportable and useful hydrolysed products. Protease activities are strictly regulated by specific inhibitors and through the activation of zymogens to develop their proteolytic activity at the right place and at the proper time. All these events associated with senescence have deep effects on the relocation of nutrients and as a consequence, on grain quality and crop yield. Thus, it can be considered that nutrient recycling is the common destiny of two processes, plant senescence and, proteolysis. This review article covers the most recent findings about leaf senescence features mediated by abiotic and biotic stresses as well as the participants and steps required in this physiological process, paying special attention to C1A cysteine proteases, their specific inhibitors, known as cystatins, and their potential targets, particularly the chloroplastic proteins as source for nitrogen recycling.