Desempenho da matriz h��brida SiO2-quitosana na imobiliza����o da lipase microbiana de Candida rugosa

Lipase from Candida rugosa was immobilized by covalent attachment on hybrid SiO2-chitosan obtained by sol-gel technique. A comparative study between free and immobilized lipase was provided in terms of pH, temperature, kinetic parameters and thermal stability on the olive oil hydrolysis. The pH and temperature for maximum activity shifted from 7.0 and 45 ��C for the free lipase to 7.5 and wide range of temperature (40-50 ��C) after immobilization. Kinetics parameters were found to obey Michaelis-Menten equation and K M values indicated that immobilization process reduced the affinity of enzyme-substrate; however Kd values revealed an increase of thermal stability of lipase.

Development and validation of a method for the analysis of tetracyclines in chicken-muscle by liquid chromatography-electrospray-mass spectrometry in tandem (LC-ESI-MS/MS)

A LC-ESI-MS/MS method was developed and validated according to the European Union decision 2002/657/EC, for the determination of tetracyclines (TCs) in chicken-muscle since Europe is one of the main markets for Brazilian products. Linearity of r > 0.9979, limits of quantification in the range of 7.0-35.0 ng/g, average recoveries of 89.38 - 106.27%, within-day and between-day precision were adequate for all TCs. The decision limit and the detection capability were 93.00-106.46 ng/g and 95.84-114.38 ng/g, respectively. This method is suitable for application in surveillance programmes of residues of TCs in chicken-muscle samples.

Adsor����o de ars��nio(V) pelo comp��sito magn��tico hidrotalcita: ��xido de ferro

In this work, hydrotalcite, a layered double hydroxide, had its adsorption and ion exchange properties combined with the magnetic properties of iron oxide to produce a magnetic adsorbent, HT-Fe. The removal of As(V) by a HT-Fe adsorbent was evaluated under various conditions. The Kinetic process was well described by a pseudo-second order rate model. The maximum adsorption capacity, calculated with the Langmuir model showed to be dependent on pH, reaching values of 24.09, 10.19 and 7.44 mg g-1, respectively, for pH values of 4.0, 7.0 and 9.0. The inhibition by competition of anions is dependent on the type of ionic species.

Adsor����o do corante vermelho congo por derivados da o-carboximetilquitosana hidrofobicamente modificados

Hydrophobically modified O-carboxymethylchitosan derivatives were synthesized through a reaction with lauroyl chloride and applied for adsorption of congo red dye. The Langmuir-Freundlich isotherm model was found to be the most suitable one for the VC adsorption and maximum adsorption capacity obtained was 281.97 mg g-1 at a pH value of 7.0 for HL 1.0. The adsorption process follows the pseudo-second-order kinetics and the corresponding rate constants were obtained. The thermodynamic parameters showed that adsorption process is spontaneous (positive ∆H��) and favorable (negative ∆G��). The hydrophobic derivatives are able to adsorb the dye even in high pH values.

Identifica����o de alguns constituintes qu��micos de Indigofera hirsuta Linn. (Fabaceae) por CLAE-IES-EM (TOF) e avalia����o da atividade antirradicalar

A rapid analytical approach, suitable to characterize the compounds present in the aqueous and methanol extracts prepared from the aerial parts of Indigofera hirsute, was developed. The method based on high-performance liquid chromatography coupled to mass spectrometry, electrospray positive ionization and detection by time of flight (HPLC-ESI-MS-TOF) identified, tryptophan, uracil, rutin, kaempferol-3-O-β-D-glucopyranoside, gallic acid and methyl gallate. The antiradical activity of this extract was evaluated using DPPH assay, with gallic acid as antiradical pattern. The study revealed the antiradical activity of methyl galatte (EC50 = 5 �� 0.3 ��g mL-1) galic acid (EC50 = 5 �� 0.2 ��g mL-1) and rutin (EC50 = 21.6 �� 0.6 ��g m L-1), isolated from methanol extract (EC50 = 67.7 �� 0.9 ��g mL-1), which showed strong antiradical activity.

Biochemical characterisation of lipase from a new strain of Bacillus sp. ITP-001

Lipases are characterised mainly by catalytic versatility and application in different industrial segments. The aim of this study was to biochemically characterise a lipase from a new strain of Bacillus sp. ITP-001. The isoelectric point and molecular mass were 3.12 and 54 kDa, respectively. The optima lipase activity was 276 U g-1 at pH 7.0 and a temperature of 80 ��C, showing greater stability at pH 5.0 and 37 ��C. Enzymatic activity was stimulated by various ions and pyridine, and inhibited by Cu+ and ethanol. The values of Km and v max were 105.26 mmol and 0.116 mmol min-1 g-1, respectively determined by the Eadie-Scatchard method.

Sor����o de Diuron em minerais da fra����o argila

The objective of the present study was to evaluate the adsorption of the herbicide Diuron onto smectite and Fe oxides minerals. Ninety mg of each mineral, 1 mL of 0.15 mol L-1 CaCl2 and 8 mL of Diuron (0.25-10.00 mg L-1) were used in triplicates. These materials were shaken, ultra centrifuged and the supernatant collected and analysed on a UV-Vis spectrophotometer. The Diuron presented low adsorption onto clay mineral fractions. Adsorption was greater onto Fe oxides at pH 7.0, possibly due to proximity to the point of zero charge of these minerals.

Extra����o de ��cido trans-trans muc��nico urin��rio com pol��meros de impress��o molecular e an��lise por cromatografia gasosa: espectrometria de massas

This paper describes selective molecularly imprinted solid-phase extraction of ttMA from urine samples followed by derivatization and analysis by gas chromatography/mass spectrometry (GC/MS). The analytical calibration curve ranged from 0.3 to 7.0 mg L-1 (r = 0.999) and the limit of quantitation (LOQ) was 0.3 mg L-1. The method was applied for the determination of ttMA in urine samples from smokers and concentrations detected ranged from < LOQ to 1.64 mg L-1. Thus, the proposed method proved adequate for the determination of urinary ttMA in the biomonitoring of occupational exposure to low levels of benzene.

Enzymatic activity of catechol 1,2-dioxygenase and catechol 2,3-dioxygenase produced by Gordonia polyisoprenivorans

This study aimed to evaluate the environmental conditions for enzyme activity of catechol 1,2-dioxygenase (C1,2O) and catechol 2,3-dioxygenase (C2,3O) produced by Gordonia polyisoprenivorans in cell-free and immobilized extracts. The optimum conditions of pH, temperature, time course and effect of ions for enzyme activity were determined. Peak activity of C1,2O occurred at pH 8.0. The isolate exhibited the highest activity of C2,3O at pH 7.0 and 8.0 for the cell-free extract and immobilized extract, respectively. This isolate exhibited important characteristics such as broad range of pH, temperature and time course for enzyme activity.

Otimiza����o da esterifica����o de ��cido hexan��ico com n-butanol empregando lipase (Termomyces lanuginosus) imobilizada em gelatina

The application of Lipozyme (Termomyces lanuginosus) immobilized in gelatin gel in aliphatic ester synthesis was investigated taking the esterification of hexanoic acid with n-butanol as a model reaction. Conditions were optimized by factorial design and the highest conversion was obtained under the following conditions: molar ratio alcohol: acid of 2:1, reaction time of 48 h and biocatalyst weight of 7.0 g. Under these conditions the esterification yield was around 98 %. The operational stability of the immobilized lipase was assessed and results showed that after 12 batch runs, the enzyme showed no significant loss of activity.

Application of cloud point preconcentration and flame atomic absorption spectrometry for the determination of cadmium and zinc ions in urine, blood serum and water samples

A simple, sensitive and selective cloud point extraction procedure is described for the preconcentration and atomic absorption spectrometric determination of Zn2+ and Cd2+ ions in water and biological samples, after complexation with 3,3',3",3'"-tetraindolyl (terephthaloyl) dimethane (TTDM) in basic medium, using Triton X-114 as nonionic surfactant. Detection limits of 3.0 and 2.0 ��g L-1 and quantification limits 10.0 and 7.0 ��g L-1were obtained for Zn2+ and Cd2+ ions, respectively. Relative standard deviation was 2.9 and 3.3, and enrichment factors 23.9 and 25.6, for Zn2+ and Cd2+ ions, respectively. The method enabled determination of low levels of Zn2+ and Cd2+ ions in urine, blood serum and water samples.

Preparation and evaluation of magnetic chitosan particles modified with ethylenediamine and Fe(III) for the removal of Cr(VI) from aqueous solutions

The adsorption of Cr(VI) in aqueous solution by magnetic particles of crosslinked chitosan-ethylenediamine-Fe(III) (MPCh-EDA-FeCL) was studied in a batch system. Fe3+ in the MPCh-EDA-FeCL permitted that adsorption of Cr(VI) occurred with maximum efficiency between pH 3 and 11. The maximum adsorption capacity at pH 7.0 was 81.04 mg g-1 at 25 &#186;C. The adsorption kinetic process was described by the pseudo-second-order model. Thermodynamic parameters indicated spontaneous, exothermic and chemical adsorption nature. The adsorbent was successively regenerated using a 0.1 mol L-1 NaOH solution. Results were satisfactory for treatment of wastewater from the electroplating industry.

USO DO PLANEJAMENTO EXPERIMENTAL PARA OTIMIZA����O DE UM PROCEDIMENTO VOLTAM��TRICO PARA DETERMINA����O SIMULT��NEA DAS CONCENTRA����ES DOS METAIS Zn, Cd, Pb E Cu LIVRES EM ��GUA DE COCO

Optimization of the main parameters of SWASV using boron-doped diamond electrode was described for the simultaneous determination of Zn, Cd, Pb and Cu free in coconut water. The values of electroanalytical parameters studied were optimized with the factorial design and center composite design. The optimized parameters for the preconcentration of metals were -1.50 V for potential, and 240 s for deposition time. For SWV, the optimized value was 11.56 mV for step potential. In addition, frequency and pulse height were defined at 100 Hz and 55 mV, respectively. Furthermore, the concentration of the supporting electrolyte (acetate buffer, pH 4.7) was optimized in 0.206 mol L-1. The optimized procedure was applied in two samples of coconut water: natural and processed. The limits of detection (LOD) obtained for Zn, Cd, Pb and Cu were 7.2; 4.4; 3.3 and 1.5 ��g L-1, respectively. The concentrations of Cd and Pb were not detected. On the other hand, the values found for the concentrations of Zn and Cu were: < LOD (29 ��g L-1) and (6.8 �� 0.9) ��g L-1 for the natural sample; and (85.8 �� 4.2) ��g L-1 and (7.7 �� 0.6) ��g L-1 for the processed sample, respectively.

M��todos de preserva����o e crescimento de Xanthomonas campestris pv. viticola em meio de cultura variando temperatura, pH e concentra����o de NaCl

A bact��ria fitopatog��nica Xanthomonas campestris pv. viticola (Xcv) causa o cancro bacteriano da videira (Vitis vinifera), que ocasiona grandes preju��zos �� viticultura no Brasil. Os m��todos de desseca����o em papel de filtro (DPF), repicagens peri��dicas (RP), ��gua destilada esterilizada (ADE) e folhas herborizadas (FH) foram utilizados para preservar duas estirpes de Xcv durante 12 meses. As vari��veis viabilidade e patogenicidade foram avaliadas mensalmente e estimadas pela obten����o de crescimento bacteriano e ��rea abaixo da curva de incid��ncia da doen��a (AACID). Tanto o m��todo de DPF como o de ADE propiciaram viabilidade constante de 100% durante 11 meses e os maiores valores de AACID. No m��todo de RP n��o houve crescimento das estirpes j�� aos 30 dias, enquanto que, em FH, Xcv foi isolada at�� cinco meses. o crescimento das estirpes de Xcv em meio de cultura l��quido variando temperatura (0, 5, 10, 15, 20, 25, 27, 28, 29, 30, 35, 40 e 45 ��C), pH (5,0; 5,5; 6,0; 6,5; 7,0; 7,5; 8,0; 8,5 e 9,0) e concentra����o de NaCl (1, 2, 3, 4, 5, 6 e 7%) foi avaliado em fotocolor��metro. O crescimento de Xcv foi observado no intervalo de 5 at�� 35 ��C, enquanto que o crescimento ��timo ocorreu de 27 a 29 ��C. A Xcv n��o cresceu a zero e 40 ��C. O pH ��timo para o crescimento desta bact��ria foi 7,5. O crescimento de Xcv decresceu a partir de 3,0% de NaCl, com concentra����o letal de 6,0%.

Determina����o de zinco em ��lcool combust��vel opr voltametria de redissolu����o an��dica

A presen��a de metais pesados em ��lcool combust��vel origina-se na produ����o e armazenamento do ��lcool et��lico, constituindo uma contamina����o inorg��nica. A an��lise quantitativa deste contaminante tem sido usualmente monitorada empregando-se t��cnicas convencionais de an��lise tal como espectrofotometria de absor����o at��mica. Tendo em vista a alta sensibilidade das t��cnicas voltam��tricas de redissolu����o an��dica para a quantifica����o de metais e que poucos estudos foram realizados para este tipo de matriz, este trabalho tem por objetivo desenvolver uma metodologia eletroanal��tica para a determina����o de zinco em ��lcool combust��vel. A determina����o eletroqu��mica para o zinco em meio aquoso utilizando-se a modalidade de varredura linear exibe uma corrente de pico an��dica em um potencial de -1,12 V vs. ECS, apresentando uma depend��ncia linear em rela����o �� concentra����o de zinco no intervalo de 5,0x10-7 a 5,0x10-6 mol.L-1 com uma sensibilidade amperom��trica de 1,2x10(6) miA.mol-1.L e um limite de detec����o de 2,6x10-7 mol.L-1. A an��lise de ��ons zinco em amostra comercial de ��lcool combust��vel foi determinada pela adi����o de 200 miL de amostra em um volume final de 20 mL de eletr��lito-suporte, sendo obtida a concentra����o de zinco na amostra pelo m��todo de adi����o de padr��o com um valor correspondente a 5,7�� 0,19x10-5 mol.L-1 em zinco.