Estudo da hidrólise enzimática e fermentabilidade em resíduos lignocelulósicos de manihot esculenta para a produção de biocombustível

Abstract

The use of fossil fuels has been causing negative impacts on the equilibrium of the environment with high levels of pollution, in view of the release of high concentrations of polluting gases in the atmosphere. Due to the growing need to minimize fossil fuel consumption and the constant search for alternative sources of clean energy, the use of lignocellulosic biomass for the production of second generation ethanol appears as an alternative. One of the great challenges in this process is the conversion of the lignocellulosic biomass to fermentable sugars, as well as, to reach a high yield in the fermentation of these. In this context, the objective of this work was to propose a preliminary study of the use of cassava residues (Manihot esculenta), aiming at the production of biofuel as a future perspective. In the first stage of this study, the chemical characterization of the biomass was carried out, which allowed the verification of the constituent components of the analyzed samples: cellulose, hemicellulose, lignin, proteins, extractives and ashes. Carbohydrates released through the enzymatic hydrolysis of the polymers were then obtained. These sugars were quantified in a High Efficiency Liquid Chromatograph (HPLC) and were subsequently submitted to a fermentation process with Saccharomyces cerevisiae. With the obtained results, it was possible to observe that the average composition of the polysaccharide cellulose has greater representativeness in the bark, with 36.12%, followed by the stem that constituted 21.52%, and finally in the leaf whose percentage was only 8.59. However, the comparison of the biotransformation profiles of cellulose to glucose showed that the bark and stem residues presented very close values (5.80 g / L and 5.56 g / L, respectively). As for the maximum ethanol production from the fermentation, it was verified that even though it had a lower glucose content than the bark, the stem was higher in the final yield (stem = 5.57 g / L, bark = 5.21 g / L). As it was observed a higher percentage of hemicellulose, and consequently a higher concentration of xylose, contributing factors for the increase in ethanol production. Based on the high carbohydrate content observed, and considering the alcoholic yields obtained from the residue of the biomass Manihot esculenta, it was possible to verify that both the stem and the bark presented representative values, which makes both strong candidates against the production of 2G ethanol .