Optimisation of glucose and levulinic acid production from the cellulose fraction of giant reed (Arundo donax L.) performed in the presence of ferric chloride under microwave heating

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.