Chitin was functionalized with hexamethylenediamine followed by glutaraldehyde activation, and its capacity to bind Candida rugosa lipase was investigated. The loading of 250 units g(-1) support showed to be effective, resulting in a uniform enzyme fixation with high catalytic activity. Both free and immobilized lipases were characterized by determining the activity profile as a function of pH, temperature, and thermal stability. For the immobilized lipase, the influence of the reaction temperature and substrate polarity in nonconventional biocatalysis was also analyzed. Production of butyl esters was found to be dependent on the substrate partition coefficient, which accounts the greatest value for the system butanol and butyric acid. The highest enzyme activity was found for the system butanol and caprylic acid at a reaction temperature of 40 degrees C. Under such conditions, the operational stability tests indicated that a small enzyme deactivation occurs after 12 batches, revealing a biocatalyst half-life of 426.7 h.

Recebido em 11/5/05; aceito em 27/10/05; publicado na web em 31/3/06 ASSESSMENT OF CATALYTIC PROPERTIES IN AQUEOUS AND ORGANIC MEDIA OF LIPASE FROM Candida rugosa IMMOBILIZED ON WOOD CELLULIGNIN ACTIVATED WITH CARBONYLDIIMIDAZOLE. 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 K m = 924.9 mM and V max = 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.Keywords: cellulignin; lipase; immobilization. INTRODUÇÃOOs processos que utilizam lipases são especialmente atraentes em função das diferentes aplicações desta enzima. As lipases podem catalisar reações de hidrólise, esterificação e interesterificação, com extrema simplicidade de processo, qualidade superior do produto final e excelente rendimento 1-3 . Estas características conferem às lipases um potencial biotecnológico comparável ao das proteases e carboidrases -enzimas industrialmente utilizadas -estimulando pesquisas para otimização da sua produção, caracterização, imobilização e aplicação industrial 2,3 .Idealmente os sistemas catalisados por lipases devem ser tratados caso a caso e as generalizações devem ser praticadas com cautela 2 . Portanto, a seleção das condições adequadas na catálise enzimática em meios não convencionais deve seguir uma cuidadosa manipulação do meio-ambiente do biocatalisador, de tal forma que a produtividade do sistema seja maximizada por meio da potencialidade total da atividade enzimática 2 . Isto pode ser alcançado pela utilização de solventes apropriados 4,5 , controle do teor de água no meio reacional 6,7 e imobilização da enzima em suportes sólidos [8][9][10] . A imobilização tem efeito benéfico na estabilidade da enzima, em função das interações físicas e químicas entre o suporte e as molécu-las da enzima. A imobilização também auxilia na dispersão homogênea da enzima no meio, o que é essencial para a condução de reações enzimáticas 9,10 .As propriedades dos derivados imobilizados são influenciadas tanto pelas propriedades da enzima como pelo material do suporte 2,11 . A interação entre esses dois componentes proporciona um derivado imobilizado...

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Pleural fluid samples collected in EDTA and sent for analysis within 1 h after collection can be used to determine ADA up to 28 days after collection if stored at 4 degrees C or -20 degrees C, with no evidence of significant increases or decrease in enzyme activity that might distort the results.

Resumo: Neste trabalho foi realizado um estudo comparativo entre as metodologias de otimização Gradiente Reduzido Generalizado (GRG) e Algoritmo Genético (AG) para a otimização de processos com múltiplas respostas. Para estimar os parâmetros que minimizam a função objetivo foram utilizadas respostas geradas por planejamento de experimentos de forma aglutinada, as quais foram incorporadas à função objetivo. Os estudos de caso utilizados foram baseados em trabalhos selecionados na literatura e, para cada experimento selecionado, foi realizada a otimização dos valores dos parâmetros do processo utilizando as duas metodologias, o GRG, por meio de uma planilha do Microsoft Excel e o AG utilizando o software Scilab. Foram realizadas 10 replicações e calculada a média dos resultados obtidos. A comparação entre os métodos foi realizada com base em medidas de desempenho, por meio da distância média percentual. O AG apresentou melhores resultados em comparação com o GRG. Palavras-chave:Otimização. Múltiplas Respostas. Algoritmo Genético. GRG. Abstract:In this paper we present a comparative study between the Generalized Reduced Gradient (GRG) and Genetic Algorithm (GA) methods to optimize multiple-response processes. Results from experiment design were used to compose the objective function to be minimized. The case studies in this work were selected from literature. A Microsoft Excel spreadsheet was used for parameters optimization using GRG, and the Scilab software was used to GA. Ten replicates were performed and the mean of the results was obtained. To assess the methods was used performance measures based on the mean percentage error. From the performance measures used, the AG showed better results compared to the GRG, indicating that the AG can generate better responses than GRG.

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Lasiodiplodan, a (1→6)-β-d-glucan, is an exopolysaccharide with high commercial value and many applications in food, pharmaceuticals, and cosmetics. Current industrial production of β-glucans from crops is mostly by chemical routes generating hazardous and toxic waste. Therefore, alternative sustainable and eco-friendly pathways are highly desirable. Here, we have studied the lasiodiplodan production from sugarcane bagasse (SCB), a major lignocellulosic agricultural residue, by Lasiodiplodia theobromae CCT 3966. Lasiodiplodan accumulated on SCB hydrolysate (carbon source) supplemented with soybean bran or rice bran (nitrogen source) was 16.2 [6.8 × 103 Da] and 22.0 [7.6 × 103 Da] g/L, respectively. Lasiodiplodan showed high purity, low solubility, pseudoplastic behavior and was composed of glucose units. Moreover, the exopolysaccharides were substantially amorphous with moderate thermal stability and similar degradation temperatures. To our knowledge, this is the first report on the highest production of SCB-based lasiodiplodan to date. L. theobromae, as a microbial cell factory, demonstrated the commercial potential for the sustainable production of lasiodiplodan from renewable biomass feedstock.