Acid/alkali-catalyzed deep eutectic solvent pretreatment of corn straw for enhanced biohydrogen production

Lignocellulose is considered as a potential source for biohydrogen production, however, the tough and rigid structure endow the lignin with high resistance to biodegradation. In this work, choline chloride/1,4-butanediol deep eutectic solvent (DES) pretreatment aiding with AlCl3/NaOH was developed to dissociate the lignin macromolecular structure of corn straw for promoting biohydrogen production. The results showed that alkali-catalyzed DES pretreatment reached a yield of biohydrogen production of 117.4 mL/g total solids (TS) in comparison with that of acid-catalyzed DES pretreatment (100.5 mL/g TS) at 100 °C for 3 h with 4.0 wt% alkali/acid dosage. The enhanced biohydrogen production was mainly ascribed to the higher lignin removal rate (81.3%) of alkali-catalyzed DES pretreatment, which facilitated subsequent enzymatic saccharification and dark fermentation of carbohydrate. Moreover, the recovered lignin obtained from this pretreatment displayed well-preserved β-O-4′ linkages (44.4/100Ar) with an appropriate molecular weight (1540 g/mol) and regular spherical particles. The new insights of this work may provide guidance for designing novel DES pretreatment toward bio-energy production from lignocellulose fractionation and component valorization.