Conversion of artichoke leftovers to levulinic acid: A biorefinery approach

The valorization of agrifood leftovers from an herbaceous plant widely cultivated in Mediterranean areas (Italy and Spain), Cynara scolymus L., is reported here as part of a zero-waste biorefinery approach. The Globe artichoke (GlobART) variety was selected as the source of artichoke leftovers, which were valorized using the following cascade approach: (i) the recovery of antioxidant compounds (AC) still present in the matrix through sustainable microwave-assisted subcritical water extraction (MA-SWE); and, (ii) the subsequent production of levulinic acid (LevA) via the MW-assisted conversion (225 degrees C, 2 min, 1500 W) of the cellulosic fraction recovered after initial extraction. Preliminary MW-assisted conversion tests on the post MA-SWE GlobART matrix yielded about a 37% yield of LevA (molar yield) using HCl and p-toluenesulfonic acid (p-TsA). Furthermore, performing a delignification step, mediated by either ultrasound (UAD) or MW (MAD), on the post-MA-SWE GlobART matrix before conversion considerably increased LevA yield (55% and 71% from post-UAD and post-MAD GlobART matrices, respectively, with p-TsA). Finally, reducing the KBr/biomass ratio, when using p-TsA, by half afforded an enhancement in LevA yield up to 80% when starting from the post-extraction and delignified (post MA-SWE-&MAD) GlobART matrix.