Produção de celulas e xilanases pelo fungo termofílio Humicola grisea var. thermoidea em diferentes substratos lignocelulósicos
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2010-08-30
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Universidade Federal de Goiás
Resumo
The vegetal biomass consists mainly of cellulose, hemicellulose and lignin. Cellulose is the most abundant polymer and xylan is the main component of hemicellulose. The conversion of cellulose and xylan to glucose and xylose can be realized by an enzymatic complex found in secretions of microorganisms such as fungi and bacteria. Enzymatic hydrolysis is an important step to the bioconversion of cellulosic and hemicellulosic fraction from lignocellulosic wastes. The thermophilic fungus Humicola grisea var thermoidea produces an efficient complex of cellulolytic enzymes (endoglucanases, cellobiohydrolases and β-glucosidase) and xylanolytic (endoxylanase and β-xylosidase) with high thermostability when grown on different lignocellulosic substrates. The aim of this study was to analyze the kinetics of production of cellulases and xylanase by the fungus H. grisea cultivated on medium containing rice straw (RS), corncob (CC), crushed cane sugar bagasse (CSB) and wheat bran (WB) as carbon source and subsequently analyze the profile of proteins with cellulolytic and xylanolytic activity secreted by the fungus when grown in minimal medium, by liquid fermentation, containing the substrates at concentrations of 1, 2 and 3% and maintained at 42 ° C, 120 rpm for different times. The best results were obtained when the fungus was grown in 3% BCA and FT, the peaks of FPase (0.17 U / mL) and CMCase (3.54 U / mL) were observed after 192 h of growth with 3% BCA , peak avicelase (0,195 U / mL) after 48 h with 3% FT and peak xylanase (23.75 U / mL) after 216 h with 3% FT. The results showed that the best inducer of enzyme production with FPase and CMCase activity was the CSB and the best inducer of enzymes production with xylanase and avicelase activity was the WB. In profile analysis of proteins secreted by H. grisea by SDS-PAGE (216 h) and zymogram (144 h), no band was seen when the fungus was grown in the presence of glucose, suggesting catabolite repression. However, two very strong protein bands corresponding to HXYN2 (23 kDa) and CBH1.2 (47 kDa) were visualized in the gels containing CSB (2 to 3%) and WB (2 and 3%). These enzymes are the main xylanolytic and cellulolytic systems of the fungus, respectively. Were monitored by recombinant enzymes from H. grisea (in gels), an endoxylanase HXYN2r (23 kDa), an cellobiohydrolase CBH1.2r (47 kDa). The masses full profile of H. grisea can be seen in Figures 13, 14, 15, 16, 18 and 19.
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MELO, Guilhermar Ramos de. Production of cellulases and xylanases by thermophilic fungus Humicola grisea var, thermoidea in different lignocellulosic sustrates.. 2010. 85 f. Dissertação (Mestrado em Ciências Biolóicas) - Universidade Federal de Goiás, Goiânia, 2010.