J.P. Cardoso
Instituto Superior Técnico
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Featured researches published by J.P. Cardoso.
Desalination | 2002
A.M. Brites Alves; A. Morão; J.P. Cardoso
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.
Separation and Purification Technology | 2001
A. Morão; A.M. Brites Alves; J.P. Cardoso
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.
Enzyme and Microbial Technology | 1983
J. M. S. Cabral; J. M. Novais; John F. Kennedy; J.P. Cardoso
Abstract Controlled pore glass was activated by transition metal salts, FeCl 2 , FeCl 3 , VCl 3 and ZrCl 4 , and derivatized by the method of Cabral et al. 1 Glucoamylase (exo-1,4-α- d -glucosidase, EC 3.2.3.1) was coupled to the aldehyde derivative, the resulting initial activities being 61.7, 71.8, 57.6 and 63.2 U g −1 of matrix, respectively. The immobilized glucoamylase preparations in which the carrier was activated with zirconium (IV) chloride displayed a very stable behaviour, with a half-life of 1709 h, in contrast with the preparations activated with iron(II) chloride ( t 1 2 = 43 7 h , iron(III) chloride ( t 1 2 = 518 h ) and vanadium(III) chloride ( t 1 2 = 893 h ). Several biocatalysts, fungal α-amylase (EC 3.2.1.1), bacterial α-amylase (EC 3.2.1.1), β- d -fructofuranosidase (invertase, EC 3.2.1.26), papain (EC 3.4.22.2) and yeast cells of Saccharomyces cerevisiae with β- d -fructofuranosidase activity were immobilized on aldehyde derivatives of titanium(IV)-activated porous silica (Spherosil), half-lives of 140, 157, 980, 236 and 413 h being obtained, respectively.
Enzyme and Microbial Technology | 1984
J. M. S. Cabral; John F. Kennedy; J. M. Novais; J.P. Cardoso
The compositions and compositional-behavioural relationships of glucoamylase (exo-1,4-α-d-glucosidase, EC 3.2.1.3) immobilized on titanium(IV)-activated porous inorganic supports have been investigated for several transition metal activation techniques based on the metal-link/chelation method developed by our group. The highest activity (239 Ug−1 matrix) of immobilized glucoamylase was obtained with the hydrous titanium(IV) oxide derivative of the support when this and a 15% w/v TiCl4 solution were dried at 45°C in vacuum for 30 h. However, the immobilized enzyme preparation displayed a very unstable behaviour, as did also the preparation which was obtained by drying the mixture of support and transition metal solution at atmospheric pressure. This was mainly due to an enzyme deactivation by titanium inhibition instead of enzyme loss in substrate solution. When amination and carbonylation steps were included in the immobilization technique much more stable preparations were obtained, mainly when the support was activated by drying at 45°C with a 15% w/v TiCl4 solution (t12 = 1495 h) although with a lower initial activity (35.6 Ug−1 matrix). The pure TiCl4 support activation rather than TiCl4/HCl solution support activation led to less stable immobilized enzyme preparations (washing and amination solvent chloroform, t12 = 365 h; washing and amination solvent water, t12 = 276 h) than the preparation obtained with the dried titanium(IV)-activated support. This was due to loss of enzyme-titanium(IV) complex in solution, as the interactions between the titanium(IV) and the silanol groups of the porous silica are weak. However, the amination (with 1,6-diaminohexane) and carbonylation (with glutaraldehyde) steps always led to immobilized enzyme preparations with constant specific activities and protein/titanium(IV) ratio. This suggests that the spacing effect introduced by these reactions removes the titanium(IV) inhibition of glucoamylase.
Enzyme and Microbial Technology | 1984
J. M. S. Cabral; J.P. Cardoso; J. M. Novais; John F. Kennedy
Abstract A simple kinetic model which describes the hydrolysis of α- d -glucans by immobilized glucoamylase (exo-1,4- d -glucosidase, EC 3.2.1.3) is reported. The hydrolysis of starch, amylose, amylopectin, maltose and 40DE starch hydrolysates using glucoamylase immobilized on alkylamine derivatives of titanium(IV) activated porous silica are described by a kinetic model based on Langmuir-Hinshelwood kinetics. This model involves enzyme kinetics with or without product inhibition and reverse reactions as well as mass transfer and diffusion effects in immobilized enzyme reactors. The results of other authors are also interpreted by the model developed in this article.
Chemical Engineering Journal | 1983
J. M. S. Cabral; J. M. Novais; J.P. Cardoso
Abstract Glucoamylase (EC 3.2.1.3.) was immobilized on controlled pore silica by a new covalent method of enzyme immobilization on inorganic supports. A 30 wt.%
Biotechnology and Bioengineering | 1981
J. M. S. Cabral; J. M. Novais; J.P. Cardoso
Journal of Chemical Technology & Biotechnology | 2007
Luís P. Fonseca; J.P. Cardoso; J. M. S. Cabral
Journal of Supercritical Fluids | 2008
M.A. Tavares Cardoso; Gabriel A. Monteiro; J.P. Cardoso; T. J. V. Prazeres; J.M.F. Figueiredo; J. M. G. Martinho; J. M. S. Cabral; António F. Palavra
Chemical Engineering Science | 2006
Ana I. Cavaco Morão; Ana Maria Brites Alves; Manuel C. Costa; J.P. Cardoso