Pier Parpot

Biomass conversion: attempted electrooxidation of lignin for vanillin production

Electrochemical oxidative degradation of Kraft lignin was investigated in batch and flow cells on Pt, Au, Ni, Cu, DSA–O2 and PbO2 anodes. Production of vanillin was evaluated by means of formal kinetic analyses. Conversion and chemical yields were found to be dependent mainly on the applied current density, that is on the partial pressure of oxygen at the interface, while the nature of the electrode influenced the reaction rates.

In situ microbial fuel cell-based biosensor for organic carbon.

The biological oxygen demand (BOD) may be the most used test to assess the amount of pollutant organic matter in water; however, it is time and labor consuming, and is done ex-situ. A BOD biosensor based on the microbial fuel cell principle was tested for online and in situ monitoring of biodegradable organic content of domestic wastewater. A stable current density of 282±23mA/m(2) was obtained with domestic wastewater containing a BOD(5) of 317±15mg O(2)/L at 22±2°C, 1.53±0.04mS/cm and pH 6.9±0.1. The current density showed a linear relationship with BOD(5) concentration ranging from 17±0.5mg O(2)/L to 78±7.6mg O(2)/L. The current generation from the BOD biosensor was dependent on the measurement conditions such as temperature, conductivity, and pH. Thus, a correction factor should be applied to measurements done under different environmental conditions from the ones used in the calibration. These results provide useful information for the development of a biosensor for real-time in situ monitoring of wastewater quality.

Potentiation of 5-fluorouracil encapsulated in zeolites as drug delivery systems for in vitro models of colorectal carcinoma

The studies of potentiation of 5-fluorouracil (5-FU), a traditional drug used in the treatment of several cancers, including colorectal (CRC), were carried out with zeolites Faujasite in the sodium form, with different particle sizes (NaY, 700nm and nanoNaY, 150nm) and Linde type L in the potassium form (LTL) with a particle size of 80nm. 5-FU was loaded into zeolites by liquid-phase adsorption. Characterization by spectroscopic techniques (FTIR, (1)H NMR and (13)C and (27)Al solid-state MAS NMR), chemical analysis, thermal analysis (TGA), nitrogen adsorption isotherms and scanning electron microscopy (SEM), demonstrated the successful loading of 5-FU into the zeolite hosts. In vitro drug release studies (PBS buffer pH 7.4, 37°C) revealed the release of 80-90% of 5-FU in the first 10min. To ascertain the drug release kinetics, the release profiles were fitted to zero-order, first-order, Higuchi, Hixson-Crowell, Korsmeyer-Peppas and Weibull kinetic models. The in vitro dissolution from the drug delivery systems (DDS) was explained by the Weibull model. The DDS efficacy was evaluated using two human colorectal carcinoma cell lines, HCT-15 and RKO. Unloaded zeolites presented no toxicity to both cancer cells, while all DDS allowed an important potentiation of the 5-FU effect on the cell viability. Immunofluorescence studies provided evidence for zeolite-cell internalization.

Electrocatalytic oxidation of saccharose in alkaline medium

Abstract The electrocatalytic oxidation of saccharose solutions was carried out in alkaline medium on various noble and non-noble electrodes, with the aim of checking the electroreactivity of saccharose and its potentiality as a raw material for electrosynthesis. The best electrocatalytic activity was obtained with gold. In this latter case, chromatographic analysis of electrolysed solutions allowed us to identify numerous monocarboxylic acids, some of them resulting from the breaking of the COC bond.

Towards implementation of a benthic microbial fuel cell in lake Furnas (Azores): Phylogenetic affiliation and electrochemical activity of sediment bacteria

This work was conducted to examine the composition and electrochemical activity of the bacterial community inhabiting lake Furnas sediments (Azores). Fingerprinting analysis of the bacterial 16S rRNA gene fragment was done by denaturing gradient gel electrophoresis. The sequences retrieved from lake Furnas sediments were affiliated to Bacteroidetes/Chlorobi group, Chloroflexi, Alfa-, Delta-, and Gamma-subclasses of Proteobacteria, Cyanobacteria, and Gemmatimonadetes. A cyclic voltammetric study was carried out with an enriched sediment bacterial suspension in a standard two chamber electrochemical cell using a carbon paper anode. Cyclic voltammograms (scan rate of 50 mV/s) showed the occurrence of oxidation-reduction reactions at the carbon anode surface. The benthic microbial fuel cell operated with lake Furnas sediments presented a low power density (1 mW/m(2)) indicating that further work is required to optimise its power generation. These results suggested that sediment bacteria, probably from the Delta- and Gamma-subclasses of Proteobacteria, were electroactive under tested conditions.

Effect of NaCl additive on properties of aqueous PEG-sodium sulfate two-phase system

The concentrations of all components in the phases of aqueous two-phase polyethylene glycol-sodium sulfate system of a fixed composition with different concentrations of NaCl additive were determined. Solvatochromic solvent features of aqueous media in the phases of all the systems were characterized in terms of solvent dipolarity/polarizability, solvent hydrogen bond donor acidity and hydrogen bond acceptor basicity. Partitioning of a homologous series of dinitrophenylated amino acids with aliphatic alkyl side chain was examined in all the systems, and the differences between the relative hydrophobicity and electrostatic properties of the phases were quantified. These differences were described in terms of solvatochromic solvent features of the phases. The previously reported partition coefficients of twelve different nonionic compounds in all the systems were expressed in terms of solute descriptors. It is demonstrated that two solvatochromic solvent descriptors (solvent dipolarity/polarizability, and solvent hydrogen bond donor acidity) could adequately describe the partitioning of the solutes in all the systems employed.

Biodegradation of ochratoxin A by Pediococcus parvulus isolated from Douro wines

Lactic acid bacteria (LAB) are a promising solution to reduce exposure to dietary mycotoxins because of the unique mycotoxin decontaminating characteristic of some LAB. Ochratoxin A (OTA) is one of the most prominent mycotoxins found in agricultural commodities. The present work reports on the ability of Pediococcus parvulus strains that were isolated from Douro wines that spontaneously underwent malolactic fermentation to detoxify OTA. These strains were identified and characterised using a polyphasic approach that employed both phenotypic and genotypic methods. When cultivated on OTA-supplemented MRS media, OTA was biodegraded into OTα by certain P. parvulus strains. The presence of OTα was confirmed using LC-MS/MS. The conversion of OTA into OTα indicates that the OTA amide bond was hydrolysed by a putative peptidase. The rate of OTA biodegradation was found to be dependent on the inoculum size and on the incubation temperature. Adsorption assays with dead P. parvulus cells showed that approximately 1.3%±1.0 of the OTA was adsorbed onto cells wall, which excludes this mechanism in the elimination of OTA by strains that degrades OTA. Under optimum conditions, 50% and 90% of OTA were degraded in 6 and 19h, respectively. Other LAB strains that belonged to different species were tested but did not degrade OTA. OTA biodegradation by P. parvulus UTAD 473 was observed in grape must. Because some P. parvulus strains have relevant probiotic properties, the strains that were identified could be particularly relevant to food and feed applications to counteract the toxic effects of OTA.

Influence of tetracycline on the microbial community composition and activity of nitrifying biofilms

The present work aims to evaluate the bacterial composition and activity (carbon and nitrogen removal) of nitrifying biofilms exposed to 50 μg L(-1) of tetracycline. The tetracycline removal efficiency and the occurrence of tetracycline resistance (tet) genes were also studied. Two sequencing batch biofilm reactors (SBBRs) fed with synthetic wastewater were operated without (SBBR1) and with (SBBR2) the antibiotic. Both SBBRs showed similar organic matter biodegradation and nitrification activity. Tetracycline removal was about 28% and biodegradation was probably the principal removal mechanism of the antibiotic. Polymerase chain reaction-denaturing gradient gel electrophoresis analysis of the bacterial community showed shifts leading to not only the fading of some ribotypes, but also the emergence of new ones in the biofilm with tetracycline. The study of the tet genes showed that tet(S) was only detected in the biofilm with tetracycline, suggesting a relationship between its occurrence and the presence of the antibiotic.

Selective oxidation of D-gluconic acid on platinum and lead adatoms modified platinum electrodes in alkaline medium

Abstract Long term electrolyses of aqueous solutions of D-gluconic acid, in alkaline medium, were carried out on smooth and upd Pb modified Pt electrodes. The reaction products in solution were analysed by ionic chromatography. It was found that the kinetics of oxidation and the orientation of the reaction depend strongly on the catalytic properties of the surface. On a smooth Pt electrode, the main products of D-gluconic acid oxidation are oxalic, tartaric, 5-keto-D-gluconic and D-glucuronic acids, while on Pt-Pb electrodes, D-gluconic acid is oxidized selectively to 2-keto-D-gluconic acid. This product and other by-products were identified by GC-MS coupling techniques.

Ultrasound enhances lipase-catalyzed synthesis of poly (ethylene glutarate)

The present work explores the best conditions for the enzymatic synthesis of poly (ethylene glutarate) for the first time. The start-up materials are the liquids; diethyl glutarate and ethylene glycol diacetate, without the need of addition of extra solvent. The reactions are catalyzed by lipase B from Candida antarctica immobilized on glycidyl methacrylate-ter-divinylbenzene-ter-ethylene glycol dimethacrylate at 40°C during 18h in water bath with mechanical stirring or 1h in ultrasonic bath followed by 6h in vacuum in both the cases for evaporation of ethyl acetate. The application of ultrasound significantly intensified the polyesterification reaction with reduction of the processing time from 24h to 7h. The same degree of polymerization was obtained for the same enzyme loading in less time of reaction when using the ultrasound treatment. The degree of polymerization for long-term polyesterification was improved approximately 8-fold due to the presence of sonication during the reaction. The highest degree of polymerization achieved was 31, with a monomer conversion of 96.77%. The ultrasound treatment demonstrated to be an effective green approach to intensify the polyesterification reaction with enhanced initial kinetics and high degree of polymerization.