Nitrite inhibition and intermediates effects on Anammox bacteria: a batch-scale experimental study

A batch test procedure, based on manometric measurements, was used to study the Anammox process, in particular the inhibition due to nitrite and the effects of hydroxylamine and hydrazine, indicated as possible intermediates of the process. The maximum nitrite removal rate (MNRR) was measured. The method showed good reliability with a standard error of 4.5 ± 3.3% (n: 41). All the tests were carried out on samples taken from a pilot plant with Anammox suspended biomass. The tests were used also to monitor the reactor activity. By testing different spiked additions of nitrite (10–75 mg NO2¯ -N L -1), a short-term inhibition, with more than 25% MNRR decrease, was found at concentrations higher than 60 mg NO2 -N L -1. Repeated additions of nitrite higher than 30 mg NO2 -N L-1 caused losses of activity. After a complete loss of activity, spiked additions of hydroxylamine (30 mg N L 1 in total) determined a 20% permanent recovery. Low amounts of the intermediates (1–3 mg N L 1) applied on partially inhibited samples and uninhibited samples produced temporary increases in activity up to 50% and 30%, respectively

An integrated approach in a municipal WWTP: anaerobic codigestion of sludge with organic waste and nutrient removal from supernatant

Co-digestion appears to be an interesting solution to increase the biogas production of poorly performing under-loaded digesters of waste activated sludge. In the Florence WWTP anaerobic codigestion could increase nitrogen and phosphorus loading rates and thus lower the nutrient removal efficiency. In order to develop an integrated solution to upgrade the Florence WWTP, the different process units were tested in experimental plants. Anaerobic codigestion with source-collected organic solid waste in a pilot-scale bioreactor showed an increase of GPR from 0.15 to 0.45 Nl biogas/l/d with 23% of organic waste loaded. Autotrophic nitrogen removal was carried out in two lab-scale pilot plants which were fed with a real anaerobic supernatant after phosphate removal via struvite formation. The nitritation MBBR has been working for one year at steady-state conditions with a perfect nitrite/ammonium ratio equal to 1:1. Anammox biomass enrichment was performed in a suspended biomass SBR and the specific nitrogen removal rate increased from 1.7 to 58 gN/kgVSS/d in 375 days

Solvent dispersible nanocomposite based on rgo surface decorated with au nanoparticles for electrochemical genosensors

A novel hybrid nanocomposite, formed of Reduced Graphene Oxide (RGO) flakes surface functionalized with 1-pyrene carboxylic acid (PCA) and decorated by Au nanoparticles (NPs), has been synthesized for the electrochemical detection of the miRNA-221 cancer biomarker. The hybrid material has been prepared by a facile approach, relaying on the in situ synthesis of the Au NPs onto the PCA carboxylic groups in presence of 3,4-dimethylbenzenethiol (DMBT) and NaBH4. The short aromatic thiol DMBT acts as reducing and coordinating agent, and hence, enables the dispersion of the nanocomposite in organic solvents. Concomitantly, DMBT favors the non-covalent anchoring of the Au NPs onto RGO, potentially allowing an efficient particle/RGO and interparticle π-π mediated electron coupling, which enhances the electron conductivity and charge transfer. PCA-RGO flakes, densely and uniformly decorated with a multilayer network of DMBT-coated Au NPs, 2.8 ± 0.6 nm in size, have been obtained, overcoming limitations previously reported for similar hybrid materials in terms of coating density and NP size distribution. Screen-Printed Carbon Electrodes (SPCEs), modified by the hybrid material and then functionalized with a thiolated DNA capture probe, have been tested for the determination of miRNA-221 in spiked human serum samples

Electrochemical detection of miRNA-222 by use of a magnetic bead-based bioassay.

MicroRNAs (miRNAs, miRs) are naturally occurring small RNAs (approximately 22 nucleotides in length) that have critical functions in a variety of biological processes, including tumorigenesis. They are an important target for detection technology for future medical diagnostics. In this paper we report an electrochemical method for miRNA detection based on paramagnetic beads and enzyme amplification. In particular, miR 222 was chosen as model sequence, because of its involvement in brain, lung, and liver cancers. The proposed bioassay is based on biotinylated DNA capture probes immobilized on streptavidin-coated paramagnetic beads. Total RNA was extracted from the cell sample, enriched for small RNA, biotinylated, and then hybridized with the capture probe on the beads. The beads were then incubated with streptavidin-alkaline phosphatase and exposed to the appropriate enzymatic substrate. The product of the enzymatic reaction was electrochemically monitored. The assay was finally tested with a compact microfluidic device which enables multiplexed analysis of eight different samples with a detection limit of 7 pmol L(-1) and RSD = 15 %. RNA samples from non-small-cell lung cancer and glioblastoma cell lines were also analyzed

Innovative biocatalysts as tools to detect and inactive nerve agents

Abstract Pesticides and warfare nerve agents are frequently organophosphates (OPs) or related compounds. Their acute toxicity highlighted more than ever the need to explore applicable strategies for the sensing, decontamination and/or detoxification of these compounds. Herein, we report the use of two different thermostable enzyme families capable to detect and inactivate OPs. In particular, mutants of carboxylesterase-2 from Alicyclobacillus acidocaldarius and of phosphotriesterase-like lactonases from Sulfolobus solfataricus and Sulfolobus acidocaldarius, have been selected and assembled in an optimized format for the development of an electrochemical biosensor and a decontamination formulation, respectively. The features of the developed tools have been tested in an ad-hoc fabricated chamber, to mimic an alarming situation of exposure to a nerve agent. Choosing ethyl-paraoxon as nerve agent simulant, a limit of detection (LOD) of 0.4 nM, after 5 s of exposure time was obtained. Furthermore, an optimized enzymatic formulation was used for a fast and efficient environmental detoxification (>99%) of the nebulized nerve agent simulants in the air and on surfaces. Crucial, large-scale experiments have been possible thanks to production of grams amounts of pure (>90%) enzymes