A. Morão

Electrochemical degradation of sulfonated amines on SI/BDD electrodes.

The electrochemical oxidation of aniline (AN) and ortanilic (OA), metanilic (MA) and sulfanilic (SA) acids was performed using as anode a boron-doped diamond (BDD) electrode. Tests were performed with model solutions of the different amines, with concentrations of 200mg L(-1), using as electrolyte 0.035 M Na2SO4, in a batch cell, with re-circulation, at different current densities (200 and 300 A m(-2)). Samples were collected at pre-selected intervals and absorbance measurements, Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), Total Kjeldahl Nitrogen, Ammonia Nitrogen, Nitrates and Nitrites and HPLC analysis were performed. Results have shown a good elimination of the persistent pollutant, with COD and TOC removals always higher than, respectively: AN--91% and 90%; OA--75% and 82%; MA--88% and 87%; and SA--85% and 79%. The combustion efficiencies, calculated for the first hour of the runs, for the 300 A m(-2) assays, were the following: AN--0.93; OA--0.28; MA--0.82; and SA--0.83. For all the amines studied, after 6h degradation only oxalic and maleic acids were identified by HPLC.

Isolation of antibiotics from industrial fermentation broths using membrane technology

Abstract Evaluation of ultrafiltration performance for the purpose of isolation of clavulanic acid from fermentation broths was carried out using two tubular ceramic membranes with molecular weight cut-offs (MWCO) of 15 and 150 kDa and two flat sheet organic membranes with MWCO of 20 and 5 kDa in order to establish the sequence of operations needed to achieve a good phase separation when the permeates are subjected to solvent extraction. Ultrafiltration fluxes are higher for the 150 kDa membrane, but the quality of its permeate is not good enough for acceptable phase separation: so, for solid—liquid separation a further purification of its permeates using the 20 kDa membrane is required. The purification of the permeates of the membrane of 20 kDa using a membrane of 5 kDa was also investigated. This last operation did not brought any improvement to the process. Ultrafiltration experiments using either the membranes of 15 kDa or of 20 kDa directly for the solid liquid separation showed that a good performance is obtained for both membranes. High fluxes and high yields of antibiotic were obtained as well as a good phase separation when their permeates were subjected to solvent extraction.

Ultrafiltration of demethylchlortetracycline industrial fermentation broths

Abstract The ultrafiltration of fermentation broths of demethylchlortetracycline (DMCT) produced at an industrial scale at CIPAN SA, has been carried out, using two ultrafiltration systems of different module geometries: a tubular module (B1 from Paterson Candy International Ltd.) and a plate-and-frame module (LabStak M20 from Danish Separation Systems). A PVDF and a fluoro polymer ultrafiltration membranes both with a MWCO of 100 KD were used. Although the highest permeate fluxes were obtained with plate-and-frame geometry, serious problems arose in cleaning the whole system, due to accumulation of solids inside the module as the broths under study are not homogeneous and contain oil–mycelium aggregates of macroscopic dimensions that cover a wide range of particle size (from less than 100 μm to about 2 mm). The results obtained for the ultrafiltration operation are also compared with those obtained for the industrial filtration using rotary vacuum filters. The same yields are achieved for about the same dilution, but ultrafiltration has the advantage of not requiring filter aid and flocculants as the conventional filtration process does. The filtrate quality is also another advantage of the membrane process, as the permeates are completely free of suspended solids. A rejection to demethylchlortetracycline related products (namely the undesirable isomer epi -DMCT) by the two membranes under study higher than that to DMCT is observed as well.

Supercoiled plasmid DNA purification by integrating membrane technology with a monolithic chromatography

The present study describes the integration of membrane technology with monolithic chromatography to obtain plasmid DNA with high quality. Isolation and clarification of plasmid DNA lysate were first conducted by a microfiltration step, by using a hydrophilic nylon microfiltration membrane, avoiding the need of centrifugation. For the total elimination of the remaining impurities, a suitable purification step is required. Monolithic stationary phases have been successfully applied as an alternative to conventional supports. Thus, the sample recovered from the membrane process was applied into a nongrafted CarbonylDiImidazole disk. Throughout the global procedure, a reduced level of impurities such as proteins and RNA was obtained, and no genomic DNA was detectable in the plasmid DNA sample. The chromatographic process demonstrated an efficient performance on supercoiled plasmid DNA purity and recovery (100 and 84.44%, respectively). Thereby, combining the membrane technology to eliminate some impurities from lysate sample with an efficient chromatographic strategy to purify the supercoiled plasmid DNA arises as a powerful approach for industrial-scale systems aiming at plasmid DNA purification.