New development of a solar electrochemical raceway pond reactor for industrial wastewater treatment.

In this work, a solar electrochemical-raceway pond reactor (SEC-RPR) is used to treat textile industrial wastewater by solar photoelectron-Fenton (SPEF) at pilot plant scale for the first time. The SEC-RPR is composed of an electrochemical filter press-cell coupled to RPR, where H2O2 is electro-generated. A complete study about experimental variables such as current, catalyst concentration, pollutant load or liquid depth is conducted based on methyl orange removal, mineralization and decolorization. Validation of the SPEF process using SEC-RPR reached more than 80% of mineralization, as well as the complete decolorization of the solution. The good performance of the SPEF treatment in the new SEC-RPR led to quick degradation kinetics, mainly due to the synergetic action of solar radiation and good distribution of H2O2 electrogenerated in the photoreactor. 100% Methyl Orange degradation was achieved after 150, 60, 45, 30 and 20 min of reaction time applying current density equal to 5, 10, 20, 40 and 60 mA cm-2, respectively. However, the increase of current density decreased the mineralization current efficiency. Up to 10 aromatics intermediates and 5 short-chain carboxylic acids were identified by LC-MS and HPLC analysis and a reaction pathway for MO mineralization by SPEF is proposed. This study represents an essential preliminary step towards the development of the first SEC-RPR at demo scale.

Review: "Pyrophosphate and pyrophosphatases in plants, their involvement in stress responses and their possible relationship to secondary metabolism".

Pyrophosphate (PPi) is produced as byproduct of biosynthesis in the cytoplasm, nucleus, mitochondria and chloroplast, or in the tonoplast and Golgi by membrane-bound H+-pumping pyrophosphatases (PPv). Inorganic pyrophosphatases (E.C. 3.6.1.1; GO:0004427) impulse various biosynthetic reactions by recycling PPi and are essential to living cells. Soluble and membrane-bound enzymes of high specificity have evolved in different protein families and multiple pyrophosphatases are encoded in all plant genomes known to date. The soluble proteins are present in cytoplasm, extracellular space, inside chloroplasts, and perhaps inside mitochondria, nucleus or vacuoles. The cytoplasmic isoforms may compete for PPi with the PPv enzymes and how PPv and soluble activities are controlled is currently unknown, yet the cytoplasmic PPi concentration is high and fairly constant. Manipulation of the PPi metabolism impacts primary metabolism and vice versa, indicating a tight link between PPi levels and carbohydrate metabolism. These enzymes appear to play a role in germination, development and stress adaptive responses. In addition, the transgenic overexpression of PPv has been used to enhance plant tolerance to abiotic stress, but the reasons behind this tolerance are not completely understood. Finally, the relationship of PPi to stress suggest a currently unexplored link between PPi and secondary metabolism.

Evidence for a non-overlapping subcellular localization of the family I isoforms of soluble inorganic pyrophosphatase in Arabidopsis thaliana.

Pyrophosphate is a byproduct of macromolecular biosynthesis and its degradation gives a thermodynamic impulse to cell growth. Soluble inorganic pyrophosphatases (PPa) are present in all living cells, but in plants and other Eukaryotes membrane-bound H+-pumping pyrophosphatases may compete with these soluble counterparts for the substrate. In Arabidopsis thaliana there are six genes encoding for classic family I PPa isoforms, five cytoplasmic, and one considered to be organellar. Here, six transgenic stable A. thaliana lines, each expressing one of the PPa isoforms from this same plant species in fusion with a fluorescent protein, were obtained and analyzed under confocal and immunogold transmission electron microscopy. The results confirmed the cytoplasmic localization for isoforms 1-5, and showed an exclusive chloroplastic localization for isoform 6. In contrast to previous reports, the data presented here revealed a differential distribution pattern for the isoforms 1 and 5, in comparison to isoforms 2 and 3, and also the presence of isoform 4 in the intercellular space and cell wall, in addition to its presence in cytoplasm. To the best of our knowledge, this is the first report of a PPa family I protein localized in the intercellular space in plants.