# Biotechnological Potential and Metabolic Diversity of Lignin-Degrading Bacteria from Decaying Tilia cordata Wood

## TL;DR

This study explores bacteria from decaying wood that can break down lignin, a complex plant polymer, and highlights their potential for biotechnological applications.

## Contribution

The paper presents a novel collection of lignin-degrading bacterial strains and their metabolic diversity from Tilia cordata wood.

## Key findings

- Sixteen ligninolytic bacterial strains were isolated, including Raoultella terrigena MGMM806, which effectively depolymerized lignosulfonate.
- The bacterial community showed high diversity and a balanced structure, with a Shannon index of 5.07.
- Isolates exhibited varied catabolic capabilities for lignin monomer degradation, indicating metabolic partitioning.

## Abstract

Lignin is a complex aromatic polymer that constitutes a major fraction of plant biomass and represents a valuable renewable carbon resource. Naturally decaying wood serves as an environmental reservoir of microorganisms capable of degrading lignin. In this study, we isolated and characterized sixteen bacterial strains from decaying Tilia cordata wood using an enrichment culture technique with lignin as the sole carbon source. Taxonomic identification via 16S rRNA gene sequencing revealed microbial diversity spanning the genera Bacillus, Pseudomonas, Stenotrophomonas, and several members of the Enterobacteriaceae family, including Raoultella terrigena isolates. Metagenomic sequencing of the wood substrate revealed an exceptionally rich and balanced bacterial community (Shannon index H′ = 5.07), dominated by Streptomyces, Bradyrhizobium, Bacillus, and Pseudomonas, likely reflecting a specialized consortium adapted to lignin rich late-stage decay. Functional phenotyping demonstrated that all isolates possess ligninolytic potential, evidenced by peroxidase/laccase-type activity through methylene blue decolorization. Dynamic Light Scattering (DLS) and HPLC analyses showed that some isolates, such as Raoultella terrigena MGMM806, effectively depolymerized lignosulfonate into low molecular weight fragments (1.23 nm), while others accumulated intermediate metabolites or completely mineralized the substrate. Growth profiling on monolignol substrates revealed a broad spectrum of catabolic specialization in lignin monomer degradation. The results demonstrate a complex system of metabolic partitioning within a natural bacterial consortium. This collection represents a foundational genetic resource for developing engineered biocatalysts and synthetic microbial communities aimed at the efficient conversion of lignin into valuable aromatic compounds.