Biocatalysis for Lignin Conversion and Valorization: Driving Sustainability in the Circular Economy

In recent years, lignin derived from lignocellulosic biomass has emerged as a critical component in modern biorefinery systems. The production yield and reactivity of lignin are critical factors for advancing the research and development of lignin-derived biochemicals. The recovery of high-purity lignin, along with carbohydrates, is accomplished through the application of various advanced pretreatment techniques. However, biological pretreatment using lignin-degrading enzymes to facilitate lignin depolymerization is an environmentally benign method for the sustainable production of valuable products that occurs under mild conditions with high substrate specificity. The current review presents the role of biocatalysis in lignin valorization, focusing on lignin-degrading enzymes that facilitate different bond cleavage in the lignocellulosic biomass. The review also highlights the recent advancements in enzyme engineering that have enabled the enhancement of enzyme stability and catalytic efficiency for improving lignin valorization processes. Furthermore, the integration of omics technologies that provide valuable insights into the microbial and enzymatic pathways involved in lignin degradation is presented. The challenges and future prospects in this emerging field of study for a biorefinery concept are also outlined for improving lignin depolymerization efficiency.