Isolation of potential lignin-degrading bacteria from tropical forest soils in Thailand

Lignin is the second most abundant polymer in plant residues and nature in general. However, lignin recalcitrance poses a challenge to biofuel production from plant biomass. To overcome the problem, this research aims to isolate bacteria strains capable of degrading lignin. Potential ligninolytic bacteria strains were isolated from 16 different soil samples based on their ability to grow on minimal media with alkali lignin as sole carbon source at 40?C under microaerobic conditions. Furthermore, growth on model lignin compounds (guaiacol and veratryl alcohol) and dyes (aniline blue, methylene blue, and Congo red) was also used to isolate four potential ligninolytic strains. Results from 16s rDNA sequence analysis showed that the four isolates belonged to genus Burkholderia, Pseudomonas, and Klebsiella. The gene encoding laccase-like multicopper oxidase was only detected in Burkholderia. Thus, the isolates identified in this study are capable of degrading lignin and may possess genes encoding for different ligninolytic enzymes which can be further explored for lignin degradation and optimization of biofuel production from plant biomass.