Understanding the Influence of Water-Soluble Compounds from Unpretreated Corn Stover Pellets on Enzymatic Hydrolysis of Cellulose

Aqueous extractives are minor and nonstructural compounds in biomass that can be extracted using solvents, while contributing significantly to lignocellulose characteristics. Yet their roles in enzyme-mediated processing of lignocellulosic biomass remain elusive. Here, we examine the composition and features of extractives derived from untreated pelleted corn stover as well as their effects on enzymatic hydrolysis. Unlike the observations described in previous reports, we find that water-extractable material improves the enzymatic hydrolysis of extractive-free stover by 67% with a glucose yield increase from 12 to 20% with 6 FPU cellulase per gram of glucan, whereas the enzyme activities are diminished when using microcrystalline cellulose (MCC) as a substrate. The different behavior of corn stover and MCC is likely attributed to the presence of lignin, which may interact with inhibitory compounds, such as phenolics, mitigating the detrimental impacts of soluble inhibitors, insoluble lignin, or both. These findings advance our fundamental understanding of the intrinsic behavior of extractives and help us to optimize the schemes for efficient and cost-competitive enzymatic conversion of lignocellulose.