Effect of sediment turbidity and color on light output measurement for Microtox Basic Solid-Phase test.

In this work, sediment samples collected from several Spanish harbours were tested with two toxicity procedures, designed for solid samples: the Microtox Basic Solid-Phase Test (BSPT) and a modified procedure of the previous test protocol (mBSPT). According to the BSPT procedure, after initial light readings, pure bacteria were exposed to sediment suspension dilutions and light production was directly measured on suspended sediments without any further manipulation. As measurements are likely to be affected by sediment turbidity and color, a variation in initial light measurement has been here suggested, in order to consider the sample effect at all time readings during the test. Firstly, when sediment suspensions at different concentrations were added to bacteria suspension, immediately the initial light output drastically decayed by more than 50% in signal difference, resulting in a false inhibition, as effect of sample turbidity/ color. This effect was more evident at high EC50 values, when slightly or not toxic samples were assessed. Secondly, the comparison of the EC50 obtained with both procedures, demonstrated that the mBSPT produced higher EC50 values (less toxic) than those obtained with the standard procedure. The mBSPT procedure resulted rapid and effective and it could be applied simultaneously with BSPT, in order to better evaluate the toxicity

Influence of chemical parameters (heavy metals, organic matter, sulphur and nitrogen) on toxicity of sediments from the Mar Piccolo (Taranto, Ionian Sea, Italy)

We studied the influence of heavy metals, organic matter (subdivided into humic compounds and not humified organic matter which represents all organic matter fractions except for humic and fulvic acids), total sulphur and nitrogen content on the toxicity of sediments from the Mar Piccolo, a semienclosed basin located near the city of Taranto (Southern Italy). In sediments, we found high level of total lead and zinc concentration but a very low bavailable metal concentrationQ, that consists in the metal fraction extractable into MgCl2 solution at pH 7, for all heavy metals. Moreover, cluster analysis pointed to a common source of organic matter, sulphur, nitrogen, lead, copper, zinc and mercury. As regards the ecotoxicological results, sediments were found to be characterized by a number of toxic units (T.U.) ranging from 1305 to 3693 T.U., indicating a medium/high toxicity level. Multiple linear regression analysis carried out using available lead, nickel and manganese concentrations, as well as sulphur and nonhumic carbon as independent variables and toxicity units as the dependent variable, accounted for a good percentage of the total variance of data (R2=91%). Nevertheless, sulphur and not humic carbon were the only significant components ( p-value: 0.022 and 0.023, respectively)

Extraction of polyhydroxyalkanoates from mixed microbial cultures: Impact on polymer quality and recovery

Polyhydroxyalkanoates (PHAs) can be extracted from mixed microbial cultures (MMCs) by means of dimethyl carbonate (DMC) or combination of DMC and sodium hypochlorite (NaClO). The protocol based on DMC, a green solvent never used before for the extraction of PHAs from MMC, allows an overall polymer recovery of 63%; also the purity and the molecular weight of the recovered polymers are good (98% and 1.2 MDa, respectively). The use of NaClO pretreatment before DMC extraction increases the overall PHA recovery (82%) but lowers the mean molecular weight to 0.6\u20130.2 MDa. A double extraction with DMC results to be the method of choice for the recovery of high quality PHAs from attractive but challenging MMCs

Impianto per trattare sostanze organiche e produrre un materiale fertilizzante

Un impianto (1) per trattare sostanze organiche fluide di scarto contenenti azoto ammoniacale e produrre un materiale fertilizzante a rilascio lento e controllato di azoto ammoniacale comprende: mezzi di miscelazione e sedimentazione (2), disposti per ricevere zeolitite e dette sostanze organiche fluide di scarto, formare una miscela contenente detta zeolitite e dette sostanze organiche fluide di scarto e consentire a detta miscela di sedimentare; mezzi vagliatori (3), disposti per vagliare detta miscela in uscita da detti mezzi di miscelazione e sedimentazione (2), in modo da separare detta zeolitite, arricchita in azoto ammoniacale e formante detto materiale fertilizzante a rilascio lento e controllato di azoto ammoniacale, da dette sostanze organiche fluide di scarto; mezzi di alimentazione (4), disposti per alimentare detti mezzi di miscelazione e sedimentazione (2) con dette sostanze organiche fluide di scarto