Influência da concentração de biomassa na produção de etanol celulósico e caracterização de uma β-glucanase de kluyveromyces marxianus

• Ano de defesa: 2014
• Autor(a) principal: Souza, Carlos Joulbert Alves de
• Orientador(a): Fietto, Luciano Gomes
• Banca de defesa: Brandão, Rogélio Lopes , Silveira, Wendel Batista da , Ramos, Juliana Rocha Lopes Soares , Guimarães, Valéria Monteze
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Bioquímica Agrícola
• Departamento: Bioquímica e Biologia molecular de plantas; Bioquímica e Biologia molecular animal
• País: BR
• Palavras-chave em Português: Biomassa; Etanol; Cana-de-açúcar; Bagaço de cana; Kluyveromyces marxianus
• Palavras-chave em Inglês: Biomass; Ethanol; Cane sugar; Bagasse; Kluyveromyces marxianus
• Área do conhecimento CNPq: CNPQ::CIENCIAS BIOLOGICAS::BIOQUIMICA
• Link de acesso: http://locus.ufv.br/handle/123456789/338

Simultaneous saccharification and fermentation (SSF) of biomass in high concentrations of solids is promising to increase the concentration of ethanol in the end of the process. However, lignocellulosic biomass is a heterogeneous and water-insoluble material and increase its concentration in the reaction medium may negatively influence the rate of conversion of biomass to ethanol. Objectives of the study were to evaluate how the increasing of solids concentration and the reactor feed mode with enzymes and biomass, have an effect on ethanol yield of a SSF process. The results show an increase of ethanol concentration with increasing of biomass concentration in all conditions evaluated. When assessing the effect of the gradual addition of enzymes, similar concentrations of ethanol were obtained, suggesting that enzymes do not significantly lose their activity during the process. The results obtained with the physico-chemical analyzes of the bagasse before and after the fermentation process suggest that the main factors influencing the enzymatic hydrolysis of biomass are lignin and cellulose crystallinity index, factors that increase throughout the process decreasing ethanol yield. Recently our research group identified a new enzyme secreted by Kluyveromyces marxianus with hydrolytic activity on cellobiose and p-nitrophenyl-β-D-glucopyranoside (PNPG). In this study the specificity of the enzyme was assessed using the substrates cellobiose (β-1, 4), CMC (β-1, 4), β-glucan (β-1, 4: β-1, 4), and PNPG. The results show a higher activity for the hydrolysis of β-glucan substrate identified indicating that the enzyme has specificity for β-1, 3 and β-1, 4 glycosidic linkages. For a better characterization of the identified enzyme protein sequencing by mass spectrometry was performed. Analyses of the sequences obtained showed high similarity to β-1, 3 glucanases from yeast. Furthermore, we measured the hydrolytic activity of this enzyme on the yeast cell wall. The results show that the enzyme has a potential application in the production of soluble β-glucan or yeast protoplast preparation. The enzyme activity of β-1, 3 ixbonds explains their activity on the cell wall of Saccharomyces cerevisiae. The amino acid sequence and specificity for β-glucans substrates suggest that the enzyme is secreted by K. marxianus one β-1-3 (4)-glucanase.