Bioethanol production from globe artichoke residues: From the field to the fermenter

The suitability of globe artichoke crop residues to be transformed into bioethanol was assessed in this paper from the field to the fermenter. A 2-year field trial on “Opera F1” (OF1), a hybrid variety of globe artichoke, resulted in an average annual production of residues of 14 t/ha. The residual biomass of OF1 is made up of 24% glucan and 17% hemicelluloses and is rich in soluble sugars. Water extraction (WE) (100 °C, 15 min) was initially applied to remove simple sugars that can be transformed into saccharification and fermentation inhibitors during the pretreatments. Subsequent dilute acid hydrolysis (DAH) (H2SO4 2%, 121 °C, 1 h) produced a slurry with 17.7, 4.2, and 0.5% (dry matter: DM) of soluble sugars, acetic acid, and total furanic compounds, respectively, and a solid fraction with 52% glucan and 14% xylan, with practically 100% digestibility. Slurry enzymatic hydrolysis (45 FPU/g DM, 7 CBU/g DM, 24 h) had a 69% glucan yield, showing an inhibition of the saccharification process due to the presence of simple sugars and inhibitors. Co-fermentation of the enzymatic slurry with Escherichia coli MS04 produced 12.5 g/L ethanol with a volumetric productivity of 0.52 g/L/h and 76.0% fermentation efficiency after 24 h of fermentation. Considering all sugars generated during DAH, the applied strategy allowed a production of 283 kg/t DM and 2399 kg/ha of bioethanol, against the theoretical value of 2806 kg/ha