Efeito de pré-tratamento hidrotérmico na hidrólise enzimática de bagaço de cana-de-açúcar

Abstract

The lignocellulosic materials as a source of renewable energy are an alternative to increase the energy matrix and reduce the environmental impacts caused by fossil fuels. In Brazil, the residue of the processing of sugar cane for sugar and ethanol sector has great potential to become raw material for ethanol production. The sector generated in the harvest of 2010/2011 about 173 million tons of sugar cane bagasse. This residue is rich in cellulose, biopolymers consisting of glucose molecules, linked by β-1,4 glycosidic bonds which can be converted to ethanol by fermentation, but one of the bottlenecks in the technology for producing ethanol from lignocellulose materials in industrial scale is a need for a pretreatment step to optimize the enzymatic hydrolysis process of the cellulose and hemicellulose to obtain fermentable sugars. The purpose of this study was to evaluate the effect of hydrothermal pretreatment with application of saturated steam, without explosive decompression and perform the hydrolysis of sugar cane bagasse pretreated hydrothermally using hemicellulolytic and cellulolytic enzymes produced by the fungus Penicillium echinulatum 9A02S1, evaluating the yield of fermentable sugars and efficiency of the pretreatment for obtaining these sugars. For this, it was performed an experimental planning CCRD (Central Composite Rotational Design) for response surface methodology (RSM) to determine the effect of the variable time of 5 min to 25 min, and the variable temperature of 169°C to 211°C. The biomass composition obtained after pretreatment were evaluated by the method of Van Soest for determination of fiber and the morphology by scanning electron microscopy (SEM), as the composition of the liquid phase resulting from the pre-treatment was assessed by high performance liquid chromatography (HPLC). Enzymatic hydrolysis was performed with enzyme load of 15 FPU/g of substrate, at 50°C, with periodic samples collection until 60h. T released sugars were measured by the DNS method for reducing sugars (RS) and PAP kit of glucose Liquiform, Labtest®. The hydrolysis of sugar cane bagasse sugar pretreated hydrothermally for 8 min and 205°C showed quantities of ARTs 698.54±46.2 mg/g dry biomass hydrolyzed after 36 h of hydrolysis reaching a gain of up to 311.8% hydrolysis after 24 hours compared to non-pretreated bagasse. This pretreatment obtained a weight loss of 14.97% of mass, due to the hydrothermal pretreatment, and the liquid phase resulting from this pretreatment there was obtained a concentration of 0.249 g/L of 5-HMF and 0.357 g/L furfural, with 2.142 g/L glucose and 3.931 g/L xylose, sugars that can be recovered. The efficiency of the pretreatment depends mainly on the residence time in the reactor and the temperature thereof, and the suitability of these parameters along with the economic attractiveness and viability of a challenge. [resumo fornecido pelo autor]