Sunday, May 3, 2009
3-27
Hemicellulose hydrolysis in South America lignocellulosic biomass by steam explosion
Cristhian Alvaro Carrasco1, Luis Fernando Quispe2, Diego Cuno2, Christian Roslander1, Mats Galbe3, and Gunnar Lidén3. (1) Chemical Engineering Department, and Instituto de Investigacion y Desarrollo de Procesos Quimicos, UMSA, Lund University, Getigenvagen 60, Lund, Sweden, Facultad de Ingenieria Universidad Mayor de San Andres - Av. Mariscal Santa Cruz, La Paz, Bolivia, Lund, Sweden, (2) Ingenieria Quimica Universidad Mayor de San Andres, Instituto de Investigacion y Desarrollo de Procesos Quimicos, Facultad de Ingenieria, Av. Mariscal Santa Cruz, La Paz - Bolivia, Bolivia, (3) Department of Chemical Engineering, Lund University, P.O. Box 124, Lund, SE-221 00, Sweden
Hemicellulose from lignocellulosic materials constitute a large potential source of fermentable sugars to be used for fuel production. Sources from the Bolivian Altiplano include e.g. Paja Brava (Stipa ichu), quinoa straw (Chenopodium quinoa Willd.) and Curupaú (Anademanthera columbrin). Those sources all have a high carbohydrate content and are already used for various purposes. The aim of the present study was to determine conditions for a good recovery of hemicellulose, primarily pentose, sugars from these materials. The three feedstocks were subjected to steam explosion using different catalyst agents. The Paja Brava and quinoa straw were SO2-impregnated (2.0 to 2.5% w/w) and steam pretreated at temperatures between 190 and 200oC, and holding times of 300 to 600 s. Curupaú hardwood, on the other hand, was hydrolyzed with dilute sulfuric acid (H2SO4 = 0.5 – 1.5 % (w/w) at a temperature of 180 to 210 °C , and a holding time between 300 and 600 s.
Acid hydrolysis gave a good recovery of pentose sugars with only minor amounts of degradation products in terms of furan compounds. Only minor proportion of the lignin was solubilized. At the conditions in the study, SO2 was the most effective catalyst tested for extraction of xylose. The quinoa and Paja Brava gave the highest xylose yields, 62% and 65%, respectively. A reasonable xylose yield (58%) was also found from the Curupaú. Acid catalyzed steam explosion thus appears to be a suitable pretreatment process for extraction of hemicellulose sugars from these feedstocks to be used in fermentation processes.
Acid hydrolysis gave a good recovery of pentose sugars with only minor amounts of degradation products in terms of furan compounds. Only minor proportion of the lignin was solubilized. At the conditions in the study, SO2 was the most effective catalyst tested for extraction of xylose. The quinoa and Paja Brava gave the highest xylose yields, 62% and 65%, respectively. A reasonable xylose yield (58%) was also found from the Curupaú. Acid catalyzed steam explosion thus appears to be a suitable pretreatment process for extraction of hemicellulose sugars from these feedstocks to be used in fermentation processes.