Unidade de Investigação – LSRE-LCM – Laboratório de Processos de Separação e Reação – Laboratório de Catálise e Materiais – Polo IPLeiria
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O polo do LSRE-LCM – Laboratório de Processos de Separação e Reação – Laboratório de Catálise e Materiais do Politécnico de Leiria foi criado em 2011 e atualmente integra o maior Laboratório Associado Português em Engenharia Química, ALiCE, com uma intervenção muito relevante nas áreas de Engenharia do Ambiente e da Bioengenharia.
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- Adsorption Behavior and Mechanism of Oxytetracycline on Rice Husk Ash: Kinetics, Equilibrium, and Thermodynamics of the ProcessPublication . Andrade, Christhel A.; Zambrano-Intriago, Luis Angel; Oliveira, Nelson S.; Vieira, Judite S.; Quiroz-Fernández, Luis Santiago; Rodríguez-Díaz, Joan ManuelThe main objective of the present study is to determine the kinetics, thermodynamics, and adsorption mechanism of the oxytetracycline (OTC) on rice husk ash (RHA). The adsorbent was characterized by scanning electronic microscopy, Fourier transform infrared spectroscopy, and nitrogen physisorption. Batch studies were carried out to evaluate the influence of the adsorbent dose, initial concentration, contact time, temperature, and initial pH. RHA was characterized as having heterogeneous, fibrous, and porous particles, consisting predominantly of silica. The removal of OTC depends on the pH of the medium, which is favored at acid pH values. The kinetic data followed the Bangham model, which indicated an OTC diffusion in the pores of RHA, although this was not the only process, as demonstrated through the use of the Weber-Morris model (IPD model). The Sips isotherm best represents the experimental results of the equilibrium study. It was found that the adsorption process was spontaneous and endothermic. The highest adsorption capacity was found at a pH in the range of 4–6, when the OTC is in its zwitterion form and the surface of the RHA is positively charged, thus permitting electrostatic interactions and the formation of hydrogen bonds between the adsorbent and adsorbate molecules. These findings demonstrate the potential of rice husk ash to remove oxytetracycline from water.
- Humic acid aggregates with laccase and decreases the performance of the enzyme catalytic systems through various mechanismsPublication . Lopes, João; Marques-da-Silva, Dorinda; Peralta, Cláudia; Rodrigues, Joaquim Rui; Vaz, Daniela; Lagoa, RicardoLaccases are among the best-rated enzymes for industrial and environmental applications, yet their use in bioremediation is limited by interference from environmental components like humic acid (HA). This study evaluated HA impact on the oxidation of 2,2 ′-azino-bis-(3-ethylbenzothiazoline-6-sulphonate (ABTS) and two model pollutants — anthracene and methyl orange — by laccase( mediator) systems. HA consistently diminished conversion rates, with EC50 values between 5 and 51 mg/L suggesting diverse inhibitory mechanisms. We investigated potential mechanisms including substrate sequestration, radical quenching, and chelation of laccase coppers by HA. Incubations with free and immobilized HA showed that adsorption can impede anthracene degradation, at least at high concentrations, but not methyl orange. Using chemically generated ABTS radical and azide-blocked enzyme, it was demonstrated that HA scavenges free radicals produced by laccase, though this alone did not fully explain the observed interference with catalysis. Further assays with metal chelator and added copper or calcium ruled out HA binding to the laccase metal centers. Instead, data from molecular docking, f luorescence, light scattering, and microscopy revealed that HA forms micrometer-scale aggregates with laccase that encapsulate the enzyme. This newly identified mechanism likely applies broadly to laccase-based systems and must be considered in applications involving aqueous media containing humic substances.
- Molecular Dissection of Escherichia coli CpdB: Roles of the N Domain in Catalysis and Phosphate Inhibition, and of the C Domain in Substrate Specificity and Adenosine InhibitionPublication . López-Villamizar, Iralis; Cabezas, Alicia; Pinto, Rosa María; Canales, José; Ribeiro, João Meireles; Rodrigues, Joaquim Rui; Costas, María Jesús; Cameselle, José CarlosCpdB is a 3′-nucleotidase/2′ 3′-cyclic nucleotide phosphodiesterase, active also with rea-sonable efficiency on cyclic dinucleotides like c-di-AMP (3′,5′-cyclic diadenosine monophosphate) and c-di-GMP (3′,5′-cyclic diadenosine monophosphate). These are regulators of bacterial physi-ology, but are also pathogen-associated molecular patterns recognized by STING to induce IFN-β response in infected hosts. The cpdB gene of Gram-negative and its homologs of gram-positive bacteria are virulence factors. Their protein products are extracytoplasmic enzymes (either periplas-mic or cell–wall anchored) and can hydrolyze extracellular cyclic dinucleotides, thus reducing the innate immune responses of infected hosts. This makes CpdB(-like) enzymes potential targets for novel therapeutic strategies in infectious diseases, bringing about the necessity to gain insight into the molecular bases of their catalytic behavior. We have dissected the two-domain structure of Escherichia coli CpdB to study the role of its N-terminal and C-terminal domains (CpdB_Ndom and CpdB_Cdom). The specificity, kinetics and inhibitor sensitivity of point mutants of CpdB, and truncated proteins CpdB_Ndom and CpdB_Cdom were investigated. CpdB_Ndom contains the catalytic site, is inhibited by phosphate but not by adenosine, while CpdB_Cdom is inactive but contains a substrate-binding site that determines substrate specificity and adenosine inhibition of CpdB. Among CpdB substrates, 3′-AMP, cyclic dinucleotides and linear dinucleotides are strongly dependent on the CpdB_Cdom binding site for activity, as the isolated CpdB_Ndom showed much-diminished activity on them. In contrast, 2′,3′-cyclic mononucleotides and bis-4-nitrophenylphosphate were actively hydrolyzed by CpdB_Ndom, indicating that they are rather independent of the CpdB_Cdom binding site.