Solid–Liquid Separation Facilitates Wash- and Detoxification-Free Bioconversion of Steam-Exploded Corn Stover

Abstract

Steam explosion (SE) pretreatment generates soluble inhibitors that hinder subsequent enzymatic hydrolysis and fermentation, thereby typically necessitating water-intensive washing or detoxification and limiting industrial feasibility. Here, we developed a simplified post-SE strategy based on solid–liquid separation (S) that circumvents both steps while maintaining efficient enzymatic hydrolysis and enabling direct fermentation of the resulting hydrolysate. Compared with direct utilization and washing, the S post-treatment achieved a glucose concentration of 42.39 g/L at a 10% solids loading, comparable to washing (45.26 g/L) and notably higher than direct utilization (36.06 g/L). Moreover, acid-assisted steam-exploded corn stover after S post-treatment (S-ASCS) supported enzymatic hydrolysis at a higher solids loading of 25%, yielding 126.89 g/L sugars. Enzymatic hydrolysis in deionized water (DW) also produced sugar concentrations comparable to those in buffered systems, indicating retained intrinsic buffering ability in S-ASCS, as supported by buffering capacity measurements. Mechanistically, this buffering behavior arose from interactions between ash-derived basic cations and weakly acidic groups released from hemicellulose acetyl cleavage. Importantly, the enzymatic hydrolysate from S-ASCS supported fermentation without additional detoxification or mineral nutrient supplementation. Overall, these findings demonstrate that solid–liquid separation represents a simplified and water-efficient alternative that preserves substrate properties required for efficient enzymatic hydrolysis and direct fermentability.

Keywords: Steam explosion, Solid-liquid separation, Wash-free enzymatic hydrolysis, Detoxification-free fermentation