Bacterial Enzyme Systems for Recalcitrant Lignocellulosic Biomass Conversion

Lignocellulosic biomass serves as the Earth’s most abundant renewable carbon reservoir, yet its industrial application is hindered by intrinsic recalcitrance, i.e., the structural resistance inherent in the cross-linked matrix. This chapter examines the role of bacterial enzyme systems as robust and adaptable biocatalysts essential for the biochemical deconstruction of these complex polymers. We provide a detailed overview of the primary bacterial enzymatic toolkit, including cellulases and hemicellulases, and the lignin-modifying enzymes that facilitate biomass valorization. A significant portion of the discussion is dedicated to the unique structural organization of cellulosomes, i.e., multi-enzyme complexes produced by specialized anaerobic bacteria that maximize catalytic efficiency through spatial proximity and substrate anchoring. Beyond naturally occurring systems, the chapter addresses the engineering of bacterial enzymes, exploring how directed evolution and rational design are employed to enhance thermal stability, pH tolerance, and catalytic turnover. By synthesizing established knowledge of bacterial enzymes, this work highlights the practical significance of these biocatalysts in the development of efficient, large-scale biorefineries and the broader transition toward a sustainable bioeconomy.