Journal of Chemical Engineering & Process Technology
Open Access

Abstract

Biorefinery of Energy Crop Cardoon(Cynara cardunculus l.)-Hydrolytic Xylose Production as Entry Point to Complex Fractionation Scheme

Anatoly A Shatalov and Helena Pereira

Response surface methodology (RSM) was employed for statistical modeling and optimization of low temperature dilute sulfuric acid hydrolysis of hemicellulose fraction of energy agro-crop cardoon (Cynara cardunculus L.), as an entry point to complex biorefinery scheme. The 23 central composite rotatable design (CCRD) was used to assess the effect of the principal independent process variables (reaction time, temperature and acid concentration) on efficiency and selectivity of heteroxylan conversion to xylose. The second-order polynomial model was fitted to experimental data to find optimal reaction conditions of xylan-to-xylose hydrolysis by multiple regression analysis. The effect of acid concentration (linear and quadratic) was found as a more significant (p=0.001-0.007) for monomeric xylose recovery in solution. The maximal xylose yield of ca. 86% (18.08 g /100 g biomass) was achieved after cardoon hydrolysis at 138.5ºC in 1.28% sulfuric acid solution for 52 min, vs. 87% predicted by model. The resulting xyloseenriched substrate revealed low concentration of toxic substances (1.04% furfural, 0.33% 5-hydroxymethylfurfural, 2.03% glucose), providing required quality for subsequent xylose (bio)conversion to final products (e.g. to xylitol). The enzymatic saccharification/digestibility of insoluble residue after hemicellulose removal was improved in four times, resulting in cellulose conversion to fermentable glucose by 76% vs. 19% for unhydrolyzed cardoon.