A review on the efficient enzymatic regulation for lignin separation from pulping pre-hydrolysis liquor

Pulping pre-hydrolysis liquor (PHL), a byproduct generated during the production of dissolving pulp, is rich in biomass resources, including hemicellulose, its degradation products, and lignin. However, due to the low lignin content, complex structure, and high reactivity, its separation and extraction remain challenging. This limitation hinders the high-value utilization of PHL, leading to biomass resource waste and exacerbating environmental pollution. Enzyme-assisted separation technology, characterized by its eco-friendliness, high selectivity, and efficiency, offers a promising strategy for the effective separation of lignin from PHL. This review systematically summarizes the recent advances in enzyme-assisted lignin separation from PHL. First, the formation process of PHL, the dissolution mechanisms of its chemical components, physicochemical properties, and potential applications are introduced. Then, the major lignin separation techniques from PHL are reviewed, with a particular focus on the latest progress in enzyme-assisted separation technologies. Furthermore, the structural characteristics of typical enzymes and their mechanisms in selectively regulating lignin extraction from PHL are discussed in detail. To identify research hotspots and key scientific challenges in this field, a keyword co-occurrence network was constructed using VOSviewer software. Based on the current technical bottlenecks, future research directions are proposed, including the development of highly efficient novel enzymes, optimization of enzyme immobilization techniques, and exploration of nanozyme applications. Finally, considering conventional pulping and papermaking processes, a process flow for enzyme-assisted lignin separation from PHL is designed to enhance lignin separation efficiency and achieve its high-value utilization.