Discovery and engineering of bifunctional enzymes for lignocellulose degradation: Metagenomic and computational approaches

Efficient degradation of lignocellulosic biomass is vital for converting plant-based waste into renewable fuels and chemicals. Owing to its complex composition of cellulose, hemicellulose, and lignin, its enzymatic breakdown often requires multiple enzymes to act synergistically. Bifunctional enzymes that combine two catalytic activities in a single protein offer a promising solution. This review highlights recent advances in the identification and engineering of bifunctional enzymes for lignocellulose degradation, particularly through metagenomics, protein fusion and computational design. Functional pairings, such as cellulase/xylanase, were examined with a focus on their synergistic effects, substrate specificity, and stability. Promiscuous and naturally evolved bifunctional enzymes from extreme or uncultured environments are also discussed. Advances <i>in silico</i> modeling and directed evolution have enhanced enzyme properties such as thermostability and substrate range. The review concludes with an outlook on the challenges and opportunities of implementing bifunctional enzymes to improve the economic and technical viability of biomass conversion.