title: Fractionation of Cynara cardunculus (cardoon) biomass by dilute-acid pretreatment.
abstract: Cynara cardunculus L. (cardoon) is a Mediterranean perennial herb offering good potential as substrate for sustainable production of bioethanol. In this work the first approach to the study of dilute-acid pretreatment of cardoon biomass for biological conversion was made. The influence of temperature (160-200 degrees C), acid concentration (0-0.2% [w/w]), and solid concentration (5-10% [w/v]) in the formation of free sugars and sugar decomposition products in the prehydrolyzate was studied using a response surface methodology. Results show a negative interaction effect between acid concentration and temperature in xylose recovery yield in prehydrolyzate, whereas dry matter concentration does not exert a significant effect. Xylose recovery yield reaches a maximum of about 80% of the content in dry untreated raw material at 180 degrees C and 0.1 or 0.2% acid addition. At these conditions the ratio of monomers found in prehydrolyzate in relation to total sugar yield for xylose is close to 100%. Furfural concentration, the major furan determined in the prehydrolyzate, increases as pretreatment severity rises. Maximum furfural yield of 4.2 g/100 g dry untreated raw material was found at 200 degrees C and 0.2% acid concentration. The yield of furfural at the conditions in which maximum xylose recovery is attained is substantially lower, less than 2 g/100 g dry untreated raw material. This fact supports the idea of using moderate temperatures in dilute-acid processes, which at the same time provides reasonably high sugar recovery yield and avoids high inhibitory products formation.
authors.affiliation: Renewable Energies Department-CIEMAT, Avda. Complutense, 22 28040, Madrid, Spain. m.ballesteros@ciemat.es
authors.forename: Mercedes
authors.initials: M
authors.lastname: Ballesteros
authors.forename: M
authors.initials: M
authors.lastname: José Negro
authors.forename: Paloma
authors.initials: P
authors.lastname: Manzanares
authors.forename: Ignacio
authors.initials: I
authors.lastname: Ballesteros
authors.forename: Felicia
authors.initials: F
authors.lastname: Sáez
authors.forename: J Miguel
authors.initials: JM
authors.lastname: Oliva
mesh_terms: D018533:Biomass; D005591:Chemical Fractionation / Q000379:methods*; D020650:Combinatorial Chemistry Techniques; D031942:Cynara / Q000737:chemistry*; D005662:Furaldehyde / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry*; D014994:Xylose / Q000737:chemistry*
chemical_list: D010936:Plant Extracts; D013464:Sulfuric Acids; D014994:Xylose; D005662:Furaldehyde; C033158:sulfuric acid