Produção de enzimas e avaliação do pré-tratamento ácido de biomassas para produção de bioetanol

• Autor(a) principal: Rodrigues, Rosilene Souza
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2421
• topic: Enzimas; Pré-tratamento; Biomasssas; Bioetanol; Enzymes; Pretreatment; Biomasses; Bioethanol; CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA::ENZIMOLOGIA

In this study the capacity of three species of fungi (Aspergillus niger LTB, Aspergillus glaucus LTB and Penicillium expansum LABQ) of producing cellulases and hemicellulases in liquid medium (0,2% yeast extract, 0,3% NaNO3, 0,05% KCl, 0,05% MgSO4.7H2O, 0,01% FeSO4.7H2O and 0,1% K2HPO4) was investigated. Carbon sources silvergrass, sugar cane bagasse and bamboo were tested for the enzyme production. Daily aliquots were removed for 15 days. The production of cellulases (FPase, cellobiase, endoglucanase e aril-β-glucosidase) and hemicellulases (α- galactosidase, L-arabinofuranosidase, β-xylosidase e xylanase) was evaluated. Besides, the characterization of the enzymes that presented high activity was made. The silvergrass was the carbon source that more efficiently induced the xylanase production for the fungi A. niger LTB, A. glaucus LTB and P. expansum LABQ; the FPase and cellobiase production for the fungus A. niger LTB; and the endoglucanase production for the fungi A. niger LTB and P. expansum LABQ. The fungus A. niger LTB was what produced larger revenues of most of the enzymes (60,76 U/g of endoglucanase, 48,7 U/g of FPase, 5320 U/g of xylanase and 228 U/g of cellobiase). The cellulases presented larger activities in acid pHs and in temperatures of 50°C and 60°C, and the FPase and the endoglucanase presented the optimum pH of 4,0. The FPase retained 76% of its activity approximately after being preincubated by 5 hours in its optimum temperature (50°C) and the endoglucanase presented 68% of residual activity after 24 hours of preincubation in its optimum temperature (60°C). The aril-β-glucosidase exhibited larger activity in pH 4,5 and in the temperature of 60°C, coming little thermostable, retaining only 15% of its activity after being incubated by 3,5 hours. The cellobiase presented values different in relation to the aril-β-glucosidase, possessing larger activity in pH 5,0 and in the temperature of 50°C, besides being more thermostable, maintaining 53% of its initial activity after preincubation for 14 hours to 50°C. The xylanase presented high activity in the strip of pH 4,0-6,0, with maximum activity in pH 5,5 and to 50°C. This enzyme was highly thermostable to 50°C, maintaining 68% of its initial activity after 24 hours of preincubation. It was also tested, in this work, several severity conditions in the dilute acid pretreatment in three lignocellulosic biomasses (silvergrass, sugar cane bagasse and bamboo), starting from the quantification of the carbohydrates in the pretreated biomass, of the reductor sugars and of the inhibitors furfural and hidroximetilfurfural (HMF). Firstly, the samples were characterized with relationship to the carbohydrates and lignin tenor. The bamboo presented around 45% of cellulose, 20% of hemicellulose and 22,5% of lignin. The sugar cane bagasse presented a tenor of approximately 43% of cellulose, 24,7% of hemicellulose and 20,2% of lignin. The silvergrass presented smaller lignin and hemicellulose tenor, with values around 18,8% and 14,5%, respectively. With relationship to the glucans tenor in the pretreated samples, there were not great difference for the biomasses. Besides, the acid hydrolysis went more efficient for the sugar cane bagasse and for the silvergrass, because 82% and 73,3% of hemicellulose were liberated of these biomasses, respectively. The bamboo lost only 65,7% of its initial hemicellulose. Likewise, for the bamboo the most suitable condition for the dilute acid pretreatment would be of 1% sulfuric acid with a treatment of 60 minutes; for the silvergrass it would be 0,5% sulfuric acid during 90 minutes; and for the bagasse it would be 0,5% sulfuric acid during 30 min. Besides, the bagasse was the biomass that was shown more promising for the bioethanol production, because it needed softer conditions and, consequently, cheaper.