Deconstructing Corn Straw Lignocellulose via Deep Eutectic Solvents to Enhance Hydrogen Production from Dark Fermentation

Abstract

Investigating avenues for sustainable energy, this study assesses the role of deep eutectic solvents (DES) in the pretreatment of corn straw to boost hydrogen output through dark fermentation. We systematically applied six DES formulations to modify the structural and compositional characteristics of corn straw. The treatments aimed to optimize enzymatic accessibility by increasing the biomass’s surface area and crystallinity and decreasing its lignin and hemicellulose contents. The enzymatic hydrolysis efficiencies for choline chloride (ChCl)/oxalic acid (OA) and ChCl/monoethanolamine (MEA), under pretreatment conditions of 100 °C for 2 h, reached 0.375 and 0.289 g/g, respectively─over four and three times higher than that of the untreated corn straw. Correspondingly, these treatments also led to significantly enhanced hydrogen yields of 123.52 and 117.06 mL/g, compared to only 0.62 mL/g from the untreated sample. This study explores the impact of different functional groups of hydrogen bond donors (HBD) in DES on the effectiveness of corn straw pretreatment. It elucidates the changes in the composition and morphology of biomass during the process and investigates the mechanisms by which these alterations influence enzymatic hydrolysis and H₂ production.