Brucella ligniniphila sp. nov., a Novel Lignin-Degrading Bacterium from Decaying Bamboo, and Synergistic Lignin Biodegradation by Consortium with White-Rot Fungi

A lignin-degrading bacterium, strain BE17T, was isolated from decaying bamboo and identified as a novel species within the genus Brucella, proposed as Brucella ligniniphila, sp. nov. (type strain = MCCC 1K08845T = JCM 36600T). BE17T exhibited a lignin degradation rate of 7.9% with lignin as the sole carbon source, which increased to 17.2% upon glucose supplementation. Structural analysis indicated that BE17T degraded lignin by cleaving β-O-4 bonds, oxidizing aliphatic side chains and disrupting aromatic rings. Low-molecular-weight lignin fractions were more readily degraded. Genome analysis revealed genes encoding DyPs, peroxidases, monooxygenases, and dioxygenases. GC-MS analysis identified aromatic monomers and organic acids among the degradation products, and together with genome annotation, these data suggested the involvement of CoA-dependent non-β-oxidative, β-ketoadipate, and phenylacetic acid pathways. To enhance lignin degradation efficiency, a co-culture system (BT) of BE17T and Trametes versicolor was established. This system achieved a degradation rate of 36.7% under optimized conditions (25 °C, pH 6.0, BE17T inoculated on day 9). Microstructural and chemical analyses confirmed that fungal pretreatment facilitated lignin degradation. This study reveals the lignin-degrading potential of a novel Brucella species and demonstrates the synergistic effect of a bacterial–fungal system, offering insights into lignin biodegradation and bioconversion strategies.