Search

A two-step exploitation of the giant reed cellulose to glucose and levulinic acid, after the complete removal of the hemicellulose fraction, was investigated using FeCl3 as catalyst. In the first step, the microwave-assisted hydrolysis of cellulose to glucose was optimised by response surface methodology analysis, considering the effect of temperature, reaction time and catalyst amount. Under the optimised reaction conditions, the glucose yield was 39.9 mol%. The cellulose-rich residue was also converted by enzymatic hydrolysis, achieving the glucose yield of 39.8 mol%. The exhausted residue deriving from the chemical hydrolysis was further converted to levulinic acid by microwave treatment at harsher reaction conditions. The maximum levulinic acid yield was 64.3 mol%. On the whole, this cascade approach ensured an extensive and sustainable exploitation of the C6 carbohydrates to glucose and levulinic acid, corresponding to about 70 mol% of glucan converted to these valuable bioproducts in the two steps.

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 &deg, 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 of32.5 and56.2 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.