Harnessing bacterial symbionts of beetles for the valorization of lignin into value‐added byproducts: Recent advances and future perspectives

Lignin is the most abundant renewable aromatic heteropolymer in nature and is highly recalcitrant due to its complex structure. The gut systems of beetles function as an evolutionarily optimized microreactor wherein mechanical pretreatment, physicochemical gradients, and selectively maintained microbial consortia act synergistically to transform, mineralize, and metabolize lignin as an energy source. Beetle-associated bacterial symbionts represent a promising yet underexploited resource for lignin valorization into value-added products. This review provides emerging evidence of lignin degradation by beetles in association with their gut symbionts and indicates the diversity of gut bacteria involved in lignin depolymerization. We further discuss the mechanisms by which beetles and their gut bacteria metabolize lignin, the lignin-transforming capacities of the bacterial symbionts and their potential application in the valorization of waste lignin into added-value byproducts. Finally, we assess the emerging research trends on the bioprospection of lignin-degrading bacteria from underexplored beetle species. Despite significant advantages, several key challenges remain unresolved, including difficulties in isolation and culturing of key gut bacteria in vitro, limited biochemical validation of candidate enzymes and the unresolved linking of specific genes or taxa to in situ lignin transformation. Future studies should integrate discovery-driven microbial ecology, multi-omics, predictive modeling and precision genome engineering to convert the complexity of beetle gut bacterial communities into a practical blueprint for scalable lignin valorization, and the biomanufacturing of high-value products from lignin-based waste.