Bioconversion of Organosolv Lignin by Rumen Bacterium: Isolation, Characterization and Metabolic Profiling

Residual lignin generated by pulp, paper, and biorefining industries is commonly burned for energy, despite its potential as a renewable source of aromatic compounds. Studies focusing on microbial lignin degradation contribute to lignin valorization and represent a sustainable strategy to enhance biomass circularity. Here, we report the isolation of Klebsiella sp. IL2_9 from a ruminal consortium and demonstrate its ability to degrade and metabolize organosolv lignin. After 24 h of cultivation, the strain removed 22% of the initial lignin content. FTIR analysis revealed alterations in functional groups associated with guaiacyl and syringyl units, indicating structural modification of the polymer. GC-MS analyses further showed the consumption of lignin-derived aromatics, including vanillin, 2-aminobenzoic acid, and 4-hydroxybenzoic acid, along with the formation of vanillyl alcohol and phenyllactic acid derivatives. Overall, these findings highlight the potential of Klebsiella sp. IL2_9 as a promising biotechnological candidate for lignin valorization under anaerobic conditions.