Multi-Step Exploitation of Raw Arundo donax L. for the Selective Synthesis of Second-Generation Sugars by Chemical and Biological Route

Abstract

Lignocellulosic biomass represents one of the most important feedstocks for future biorefineries, being a precursor of valuable bio-products, obtainable through both chemical and biological conversion routes. Lignocellulosic biomass has a complex matrix, which requires the careful development of multi-step approaches for its complete exploitation to value-added compounds. Based on this perspective, the present work focuses on the valorization of hemicellulose and cellulose fractionsof giant reed (Arundo donax L.) to give second-generation sugars, minimizing the formation of reaction by-products. The conversion of hemicellulose to xylose was undertaken in the presence of the heterogeneous acid catalyst Amberlyst-70 under microwave irradiation. The effect of the main reaction parameters, such as temperature, reaction time, catalyst, and biomass loadings on sugars yield was studied, developing a high gravity approach. Under the optimised reaction conditions (17 wt% Arundo donax L. loading, 160 °C, Amberlyst-70/Arundo donax L. weight ratio 0.2 wt/wt), the xylose yield was 96.3 mol%. In the second step, the cellulose-rich solid residue was exploited through the chemical or enzymatic route, obtaining glucose yields of 32.5 and 56.2 mol%, respectively. This work proves the efficiency of this innovative combination of chemical and biological catalytic approaches, for the selective conversion of hemicellulose and cellulose fractions of Arundo donax L. to versatile platform products.

Synergistic Catalytic Effect of Sulphated Zirconia—HCl System for Levulinic Acid and Solid Residue Production Using Microwave Irradiation

“…The relative crystallinity of the raw biomass, solid residue from SZR in water medium and 10 mM HCl catalysis was 77.8%, 88.3% and 93.5%, respectively. This strongly suggests that the SZR favourably removes amorphous cellulose, which is in agreement with the effects of other solid acid catalysts in the literature [52]. The addition of 10 mM HCl significantly increases the degradation of amorphous cellulose compared to the water medium, which could be indicative of the role of trace HCl in cellulose depolymerisation.…”

Arundo donax Refining to Second Generation Bioethanol and Furfural

“…Strong cation-exchange resins offer the advantages of continuous processing of pretreatment liquid, reusability and short reaction times when compared to enzymes. One limitation is the thermal instability at temperatures of 150-170 • C, typically used for oligosaccharide hydrolysis [48]. Considering that the microwave-assisted processes typically last less than other thermal processes, the extent of the resin's deactivation is expected to be limited.…”

Sustainable Exploitation of Residual Cynara cardunculus L. to Levulinic Acid and n-Butyl Levulinate

“…The peak at 1734 cm −1 is due to C=O stretching in the acetyl group and carboxylic acid of hemicellulose, while the signals at 1600 and 1510 cm −1 are attributed to aromatic C=O stretching and C=C vibration of lignin [41,42]. Weak peaks are observed at 1422, 1375 and 1318 cm −1 that can be assigned to the C-H asymmetric mode of CH2 in cellulose, aromatic C-H and C-O in lignin, respectively [43,44]. The band at 1239 cm −1 is due to the C-O stretching of alcoholic, phenolic and ether groups [44].…”