Fabrício Maciel Gomes

Influence of storage time and temperature on pleural fluid adenosine deaminase determination

Objectives and background:  The determination of adenosine deaminase (ADA) activity in pleural fluid is important for differentiation of pleural effusions and diagnosing pleural tuberculosis. Although measurement of ADA is simple and inexpensive, controversies exist regarding potential errors caused by time elapsed between sample collection and analysis, storage temperature and the use of anticoagulants. The objective of this study was to evaluate the influence of storage time (1, 3, 7, 10 and 28 days) and temperature (4°C and −20°C) on the determination of ADA in pleural fluid samples collected in EDTA and sent at ambient temperature to the laboratory for initial processing within 1 h of collection.

Wood Cellulignin as an Alternative Matrix for Enzyme Immobilization

The objective of this work was to select an efficient methodology for preparing active samples of Candida rugosa lipase immobilized in wood cellulignin, to be applied in hydrolysis and ester reactions. For this purpose, lipase was immobilized in the matrix by physical adsorption (pure cellulignin) and covalent binding (activated cellulignin with glutaraldeyde or carbonyldiimidazole [CDI]) in the presence or absence of polyethylene glycol (PEG) (Molecular mass of 1500 Daltons) as stabilizing agent. The activating agent and the presence of PEG-1500 in the immobilization procedure showed a strong influence on enzyme retention in the support. The values for enzyme retention ranged from 20 to 68%, and the highest yield was obtained when the enzyme was immobilized in cellulignin activated with CDI in the presence of PEG-1500. This immobilized derivative presented high hydrolytic (193.27 microM/[mg.min]) and synthetic (522.92 microM/[g.min]) activities when compared with those obtained by other techniques. The superiority of this immobilized system was confirmed by additional analyses, such as infrared spectroscopy and elemental analysis, which demonstrated an appropriate enzyme fixation and the highest level of protein incorporation in the support. Further information on the immobilized derivative was obtained by assessing the recycle potential in both aqueous and nonaqueous media.

DETERMINAÇÃO DAS PROPRIEDADES CATALÍTICAS EM MEIO AQUOSO E ORGÂNICO DA LIPASE DE Candida rugosa IMOBILIZADA EM CELULIGNINA QUIMICAMENTE MODIFICADA POR CARBONILDIIMIDAZOL

Microbial lipase from Candida rugosa was immobilized by covalent binding on wood cellulignin (Eucaliptus grandis) chemically modified with carbonyldiimidazole. The immobilized system was fully evaluated in aqueous (olive oil hydrolysis) and organic (ester synthesis) media. A comparative study between free and immobilized lipase was carried out in terms of pH, temperature and thermal stability. A higher pH value (8.0) was found optimal for the immobilized lipase. The optimal reaction temperature shifted from 37 °C for the free lipase to 45 °C for the immobilized lipase. The pattern of heat stability indicated that the immobilization process tends to stabilize the enzyme. Kinetics tests at 37 °C following the hydrolysis of olive oil obeyed the Michaelis-Menten rate equation. Values for Km = 924.9 mM and Vmax = 198.3 U/mg were lower than for free lipase, suggesting that the affinity towards the substrate changed and the activity of the immobilized lipase decreased during the course of immobilization. The immobilized derivative was also tested in the ester synthesis from several alcohols and carboxylic acids.

Chemometric Methods for the Optimization of the Advanced Oxidation Processes for the Treatment of Drinking and Wastewater

Advanced Oxidative Processes (AOP) have been successfully employed as efficient water treatment methods. The utilization of AOP on drinking and wastewater represents currently an alternative to costly, hazardous, and slow processes. In order to further establish the ground basis for AOP in water safety and security, reliable and consistent methods of analysis are required. As an alternative to basic statistical methods, which may not successfully describe and forecast the application of a given treatment methodology of water, the use of chemometrics has increased significantly over the past decades. Chemometric analyses are an intersection between analytical chemistry and applied statistical models in order to predict and extract information from a given condition. This chapter introduces the concepts of chemometrics in environmental engineering issues and the utilization of experimental design to efficiently analyze experimental data in environmental samples. Two case studies are presented to demonstrate the importance of chemometrics in water analyses: (1) considering a Taguchi L16 experimental design, and an optimization study using Response Surface Methodology, to evaluate photo-Fenton and ozone AOP-based treatment on an effluent with high concentration of organic matter; (2) using a Taguchi L9 array to evaluate the combination of photocatalytic degradation and AOP of an industrial effluent. The results showed in this chapter demonstrate how a given statistical method can be successfully employed within the intersection of environmental analyses and water issues.