Sacarificação enzimática de bagaços de cana-de-açúcar pré-tratados com sulfito ácido

Abstract

A Deus, por me dar a vida e me manter sempre firme nos meus propósitos. À Professora Dra. Adriane Maria Ferreira Milagres, pela orientação, amizade, confiança e disponibilidade.À minha mãe, Maria José, in memoriam, por todos os ensinamentos e anos dedicados a moldar meu caráter e me encher de amor e carinho.Ao meu pai, Marcelo Monte, pelo exemplo de sabedoria, força e persistência.Às minhas filhas, gêmeas, presentes de Deus, Mariana e Cecília, que chegaram para me dar força e ânimo para vencer mais essa etapa e com seus 'chutinhos' me incentivaram a terminar a escrita da tese.Aos meus irmãos Marcelo, Regina, Isabel e Elisa que mesmo à distância sempre me incentivaram, apoiaram e confiaram em mim.Ao meu marido, Renato, pela paciência, amor e apoio constante. The enzymatic hydrolysis of sugarcane bagasse, to obtain a high efficiency of conversion of polysaccharides in monosaccharides, is dependent on factors related to the morphology and chemical composition. Therefore, a pretreatment step is necessary in order to obtain a less recalcitrant substrate. The main objective of this work was to study acid sulfite pretreatment in different samples of sugarcane bagasse, to verify how the changes in the fibers could influence the enzymatic conversion of cellulose. The methodology of acid sulfite pretreatment is based on the chemical modification of the substrate by removing hemicellulose and lignin sulfonation, followed by mechanical refining. The effect of the addition of Na 2 SO 3 at concentrations of 0 to 10 % (w/w) with constant loading of 2.5 % (w/w) H 2 SO 4 was evaluated to pretreat commercial variety of bagasse (VC) at 121 °C. The effect on the variation of pretreatment temperature (130 °C, 150 °C and 160 °C) was evaluated to the acid sulfite reaction with the VC and hybrids H89, H146, H166. The changes in the chemical composition of bagasses were determined, as well as the sulfonic acid groups content, the degree of water retention value and the X-rays diffraction pattern. Methods such as scanning electron microscopy, FTIR and thermal analysis (TGA and DSC) completed the characterization of the pretreated bagasse. The effect of enzyme loading was evaluated in the hydrolysis of pretreated bagasse, fixing the consistency at 2 % (w/v) and cellulases derived from Trichoderma reesei mixed by β-glucosidase of Aspergillus niger in enzyme loadings of 5:10, 10:20 and 20:40 FPU:IU, respectively. It was observed that increasing the sulfite loadings, as well the temperature of pretreatment resulted in high removal of hemicellulose and lignin. The removal of hemicellulose reached 70 % in the pretreated bagasses at 160 °C. The water retention values were lower in bagasses with low hemicellulose content and the crystallinity index (ICcorr) calculated and corrected by pretreatment yields increased under high temperature. The severity factor pretreatment did not correlate with the enzymatic conversion of cellulose and hemicellulose, but the highest removal of hemicellulose promoted a better action of enzymes on substrates. The ef...