Monday, May 4, 2009
12-24
Optimization and kinetics of lime pretreatment of sugarcane bagasse to enhance enzymatic hydrolysis
Laura L. G. Fuentes, Daniella R. Garcia, Sarita C. Rabelo, Rubens Maciel Filho, and Aline C. Costa. Department of Chemical Process – School of Chemical Engineering, State University of Campinas, Cidade Universitária, Campinas, Brazil
Renewable energy sources, such as lignocellulosic biomass, are environmentally friendly because they emit less pollution without contributing for net carbon dioxide to atmosphere. Among lignocellulosic biomass, sugarcane bagasse is an economically viable alternative to produce biofuels. The objective of this work is to study the pretreatment of sugarcane bagasse with lime to enhance enzymatic hydrolysis and subsequent ethanol fermentation. The first stage was an evaluation of the influence of solids loading (4-10%) and stirring speed (150-350rpm) during pretreatment on sugars yields after hydrolysis. Afterwards, a 23 central composite design was performed to determine the values of temperature, reaction time and lime mass that maximize glucose release after hydrolysis. The maximum glucose yield was 228,45mg/g raw biomass, corresponding to 409.9 mg/g raw biomass of total reducing sugars, with the pretreatment performed at 90ºC, for 90 h and with 0,4 g Ca(OH)2/g dry biomass. The enzymes loading was 5FPU/dry pretreated biomass of cellulase and 1CBU/ dry pretreated biomass of b-glucosidase. After the optimal conditions were determined, kinetic data of the pretreatment were obtained for different temperatures (60, 70, 80 and 90ºC) as a function of time. Bagasse composition (cellulose, hemicellulose and lignin) was measured and the study has shown that 50% of the original material was solubilized, lignin and hemicellulose were selectively removed, but cellulose was not affected by lime pretreatment in mild temperatures (60 – 90ºC). The delignification is highly dependent of temperature and time.