title: Evaluation of steam explosion pre-treatment for enzymatic hydrolysis of sunflower stalks.
abstract: Sunflower stalks, a largely available and cheap agricultural residue lacking of economic alternatives, were subjected to steam explosion pre-treatment, the objective being to optimize pre-treatment temperature in the range 180-230°C. Enzymatic hydrolysis performed on the pre-treated solids by a cellulolytic complex (Celluclast 1.5L) and analysis of filtrates were used to select the best pre-treatment temperature. Temperature selection was based on the susceptibility to enzymatic hydrolysis of the cellulose residue and both the cellulose recovery in the solid and the hemicellulose-derived sugars recoveries in the filtrate. After 96h of enzymatic action, a maximum hydrolysis yield of 72% was attained in the water-insoluble fiber obtained after pre-treatment at 220°C, corresponding to a glucose concentration of 43.7g/L in hydrolysis media. Taking into account both cellulose recovery and hydrolysis yield, the maximum value of glucose yield referred to unpretreated raw material was also found when using steam pre-treated sunflower stalks at 220°C, obtaining 16.7g of glucose from 100g of raw material. With regard to the filtrate analysis, most of the hemicellulosic-derived sugars released during the steam pre-treatment were in oligomeric form, the highest recovery being obtained at 210°C pre-treatment temperature. Moreover, the utilisation of hemicellulosic-derived sugars as a fermentation substrate would improve the overall bioconversion of sunflower stalks into fuel ethanol.
authors.affiliation: Department of Chemical, Environmental and Materials Engineering, University of Jaén, Campus Las Lagunillas, 23071 Jaén, Spain.
authors.forename: Encarnación
authors.initials: E
authors.lastname: Ruiz
authors.forename: Cristóbal
authors.initials: C
authors.lastname: Cara
authors.forename: Paloma
authors.initials: P
authors.lastname: Manzanares
authors.forename: Mercedes
authors.initials: M
authors.lastname: Ballesteros
authors.forename: Eulogio
authors.initials: E
authors.lastname: Castro