RESUMO
One full-length ß-xylosidase gene (hxylA) was identified from the Humicola grisea var. thermoidea genome and the cDNA was successfully expressed by Pichia pastoris SMD1168. An optimization of enzyme production was carried out, and methanol was found to be the most important parameter. The purified enzyme was characterized and showed the optimal conditions for the highest activity at pH 7.0 and 50°C, being thermostable by maintaining 41% of its activity after 12h incubated at 50°C. HXYLA is a bifunctional enzyme; it showed both ß-xylosidase and α-arabinfuranosidase activities. The Km and Vmax values were 1.3mM and 39.1U/mg, respectively, against 4-nitrophenyl ß-xylopyranoside. HXYLA showed a relatively strong tolerance to xylose with high Ki value of 603mM, with the xylose being a non-competitive inhibitor. HXYLA was successfully used simultaneously and sequentially with an endo-xylanase for analysis of synergism in the degradation of commercial xylans. Furthermore, commercial cellulases supplementation with HXYLA during sugarcane bagasse hydrolysis increased hydrolysis in 29%. HXYLA is distinguished from other ß-xylosidases by the attractive characteristics for industrial applications such as thermostability, high tolerance xylose and saccharification of biomass by convert xylan into fementable monosaccharides and improve cellulose hydrolysis.
Assuntos
Celulose/metabolismo , Proteínas Recombinantes/metabolismo , Saccharum/química , Xilose/farmacologia , Xilosidases/metabolismo , Concentração de Íons de Hidrogênio , Hidrólise , Metais/farmacologia , Pichia/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Análise de Sequência , Especificidade por Substrato , Xilosidases/química , Xilosidases/genéticaRESUMO
Foi pesquisada a presença dos fatores de colonizaçäo CFAI, CFAII (CS1-CS) e CFAIV (CS4-CS6) em 87 amostras estudadas neste trabalho foram isoladas de casos de diarréia e crianças abaixo de 12 anos, nas regiöes de Ouro Preto (MG) e Paulínia (SP). Apenas duas amostras de Ouro Preto (2,3 por cento do total estudado), ambas capazes de produzir STa, apresentaram sorologia positiva para CFAI. Näo foram encontradas amostras com características hemaglutinantes D-manose resistente para uma ou mais das seguintes hemáceas: humanas, bovinas e de galinha
