In the process of converting lignocellulose to biofuels, lignin is one of the major obstacles. To overcome this recalcitrance, exploring bacteria with higher delignification efficiency or novel enzymes has been highlighted. In this study, eight bacteria isolated from termite guts were evaluated for their lignolytic potential. Among the isolates, Raoultella ornithinolytica MP-132 was selected for further investigation based on its capacity to use a broad range of monomeric and dimeric aromatic compounds as carbon source. Subsequently, the structural evolution of milled wood lignin (MWL) was evaluated by FTIR and TGA. The analysis results showed the cleavage of various chemical linkages, destruction of aromatic ring structures, side-chain oxidation and demethoxylation or demethylation by comparing the different peak intensities in the corresponding curve of each sample. In addition, the thermal stability of MWL increased after bacteria treatment, indicating the structural change in MWL caused by treatment with strain MP-132. These results demonstrated that Raoultella ornithinolytica MP-132 may be a potential candidate for the lignocellulosic bioenergy industry.