Effects of different pre-treatments on the properties of polyhydroxyalkanoates extracted from sidestreams of a municipal wastewater treatment plant.

The paper deals with effects of two different widespread extraction methods (conventional extraction and Soxhlet extraction) and four different pre-treatments (homogenization with pressure and with blades, sonication, and impact with glass spheres) on the extraction yields and properties of polyhydroxyalkanoate (PHA) extracted from biomass coming from an innovative process (short-cut enhanced phosphorus and PHA recovery) applied in a real wastewater treatment plant. The results show that the two different extraction processes affected the crystallization degree and the chemical composition of the polymer. On the other hand, the extractive yield was highly influenced by pre-treatments: homogenization provided a 15% more extractive yield than the others. Homogenization, especially at high pressure, proved to be the best pre-treatment also in terms of the purity, visual appearance (transparency and clearness), thermal stability, and mechanical performances of the obtained PHA films. All the PHA films begin to melt long before their degradation temperature (Td > 200 °C): this allows their use in the fields of extrusion or compression moulding. SYNOPSIS: Optimizing the extraction of PHAs from municipal wastewater gives a double beneficial environmental impact: wastewater treatment and circular bio-based carbon upgrade to biopolymers for the production of bioplastics and other intersectoral applications.

Reactivity of ubiquinones and ubiquinols with free radicals.

The reactivity of quinones 1-4 and of the corresponding quinols 5-8 towards carbon- and oxygen-centred radicals were studied. All quinones bearing at least one nuclear position free, readily react with alkyl and phenyl radicals to afford the alkylated quinones 12-24; however, quinones 1 and 3 reacted with 2-cyano-2-propyl radical to yield products (the mono- and di-ethers 9-11) derived from the attack on the carbonylic oxygen. The reactions carried out on quinones with the benzoyloxy radical led to no reaction products and in the case of Q10, the isoprenic chain also remained unchanged. Quinols 5-8 reacted only with oxygen-centred radicals (benzoyloxy and 2-cyano-2-propyl-peroxy radicals) to give the corresponding quinones. The isoprenic chain of Q10 did not undergo attack even with peroxy radicals. Carbon-centred radicals resulted unable to abstract hydrogen from the studied quinols.

Reactivity of an indolinonic aminoxyl with superoxide anion and hydroxyl radicals.

The increasing knowledge on the participation of free radicals in many diverse clinical and pathological conditions, has consequently expanded the search for new and versatile antioxidants aimed at combating oxidative stress. Our interest in this field concerns aromatic indolinonic aminoxyls (nitroxides) which efficiently react with alkoxyl, peroxyl, aminyl, arylthiyl and alkyl radicals to give non-paramagnetic species. This prompted us to test their antioxidant activity on different biological systems exposed to free radical-induced oxidative stress and the results obtained so far have been very promising. However little is known about their behaviour towards superoxide and hydroxyl radicals. Here, we report on the reactivity of an indolinonic aminoxyl, with the two above mentioned radicals using hypoxanthine/xanthine oxidase and potassium superoxide for generating the former and the Fenton reagent for the latter. Besides performing the deoxyribose assay for studying the reaction of the aminoxyl with hydroxyl radical and monitoring spectral changes of the aminoxyl in the presence of superoxide radical, macroscale reactions were performed in both cases and the products of the reactions isolated and identified. The EPR technique was used in this study to help elucidate the data obtained. The results show that this compound efficiently reacts with both hydroxyl and superoxide radicals and furthermore, it is capable of maintaining iron ions in its oxidized form. The results thus contribute to increasing the knowledge on the reactivity of indolinonic aminoxyls towards free radical species and as a consequence, these compounds and/or other aminoxyl derivatives, may be considered as complementary, and sometimes alternative sources for combating oxidative damage.

Beta-phosphorylated five membered ring nitroxides. Synthesis and EPR study.

A series of stable beta-phosphorylated five membered ring nitroxides was prepared by intramolecular aminomercuration of alkenyl alpha-aminophosphonates. The structure of these nitroxides was deduced from their 13C and 31P coupling constants and from force field calculations.