Estudo e otimização de tratamentos hidrolíticos para o aproveitamento de biomassas

Abstract

Biomasses of lignocellulosic matrix like as Rice Husk (RH) and microalgae (MA) are potential feedstocks for the production of fermentable monosaccharides and bioproducts. Thus, this research work had as main objective to study and optimize the pretreatment steps for hydrolysis and fermentation, and for this it was applied, initially, alkaline treatment (with NaOH, Ca(OH)2, KOH, CaCO3 and NH4OH), under atmospheric pressure, optimized by Central Composite Rotatable Design (DCCR). Subsequently, it was applied pressurized acidic hydrolysis of RH (34-48 bar), using diluted HCl and H2SO4. The best results for the RH pretreatment were obtained with KOH (65 °C, 60 min, 4.25% w v-1 alkali), and with NaOH (65 °C, 35 min, 4.25% w v-1 alkali), producing fermentable sugars at concentrations of 24.0 e 21.7 g L-1. In the following pressurized hydrochloric hydrolysis, it was obtained productivity of 12.8 g L-1 (162 °C, 45 min, 2.5% v v-1 acid) and, 13.5 g L-1 for the pressurized sulfuric hydrolysis (155 °C, 55 min, 3.5% v v-1 acid). In the case of MA in natura, for pressurized hydrochloric hydrolysis, it was obtained productivity of 10.0 g L-1 (150 °C, 45 min, 0.5% v v-1 acid) and, for the pressurized sulfuric hydrolysis, 13.56 g L-1 (152 °C, 55 min, 2.0% v v-1 acid). Now, for the residual microalgae, it was obtained productivity of 8.42 g L-1 by the pressurized hydrochloric hydrolysis (150 °C, 40 min, 0.5% v v-1acid) and, 8.45 g L-1, by the pressurized sulfuric hydrolysis (140 °C, 37 min, 0.5% v v-1 acid). The fermentability of the hydrolysates was confirmed (consumption >95% of sugars) by the Rhizobium radiobacter. The analytical technique used was HPLC-RID, including study of the figures-of-merit and method validation. Based on the obtained productivities, it is possible to conclude that the studied biomasses can be looked as viable sources of fermentable monosaccharides.