Enhanced Enzymatic Hydrolysis of Pine Wood Chips by Two-Step Pretreatment Combining Steam Explosion and Urea

Abstract

Lignocellulosic biomass such as pine wood offers a renewable alternative to fossil resources but remains challenging to convert due to its recalcitrant structure. Efficient pretreatment is essential to overcome this limitation and enable enzymatic hydrolysis. This study aimed to enhance enzymatic saccharification of pine wood chips through a two-step pretreatment combining steam explosion and urea treatment. Pine wood chips were first subjected to steam explosion to degrade hemicellulose and modify lignin structure, followed by ambient-temperature urea treatment (0.5 to 2%) to disrupt hydrogen bonding and increase porosity. Comprehensive chemical, structural, and morphological analyses were conducted, including BET surface area measurements and SEM imaging. The integrated pretreatment significantly improved enzymatic digestibility, with a maximum hydrolysis yield of 82% achieved at 1% urea concentration. Key factors contributing to this enhancement included increased surface area, reduced lignin–enzyme interactions, and improved cellulose accessibility. The combined treatment outperformed either method alone in terms of glucose release. These findings demonstrate the potential of a steam explosion–urea strategy as a cost-effective and scalable approach for pine wood bioconversion within an integrated biorefinery framework.