Hidrólise enzimática da palha de cana-de-açúcar pré-tratada com hidróxido de sódio

Abstract

In recent years, special attention has been given to the reuse of waste generated in the various industrial processes. Several bioprocesses have been developed using these materials as substrates for the production of several high value-added molecules, such enzymes. Among the various enzymes, the cellulases stand out for being highly specific biocatalysts that act in synergy for the release of sugars, of which glucose is the one that shows greater industrial interest due to the possibility of their conversion into cellulosic ethanol. Therefore, the aim of this study was to characterize the chemical composition of untreated and pre-treated sugarcane straw and to evaluate the enzymatic hydrolysis of pretreated straw, using cellulases and xylanases enzymes produced from Penicillium sp. FSDE 15 and Aspergillus sp. FSDE 16 filamentous fungi, by solid-state fermentation. The chemical pretreatment conditions (NaOH concentration of 3%, temperature of 120 °C and time of 90 min) were established from an experimental factorial design of 23 with three central points. Enzymatic hydrolysis of pre-treated sugarcane straw was performed in 125 mL Erlenmeyer flasks containing 3 g of sugarcane straw, sodium citrate buffer (50 mM, pH 4.8) and enzyme loading of 1.25 FPU/mL. The results for the lignocellulosic characterization obtained for untreated cane straw (29.52% cellulose, 27.08% hemicellulose, 19.35% lignin, 3.57% extractives and 6.09% ashes) and for pre-treated cane straw (60.19% cellulose, 17.97% hemicellulose, 8.49% lignin, 2.87% extractives and 5.45% ash) demonstrated that the pre-treatment step with NaOH was satisfactory, with a good removal of lignin (solubilization of 56.12%). Through the fermentative tests (70% humidity, 38 °C and spore concentration of 106), it was possible to reach a maximum production of CMCase, FPase and xylanase of 1.63 U/mL, 0.092 U/mL and 20.73 U/mL, respectively, for tests with cane straw and wheat bran. Analyzing the enzymatic hydrolysis, the highest concentration of A.R.T. for the enzymatic loading of 10 FPU/g was 36.01 g/L in 48 hours of hydrolysis and, for the loading of 5 FPU/g, that value was 16.35 g/L, in 24 hours of hydrolysis. These results show the good use of sugarcane straw as well as the Penicillium sp. FSDE 15 in the release of glucose