Lignin-Degrading Microorganisms from Organic Soils

The most prevalent aromatic polymer in nature is lignin, produced by higher plants and thought to make up 30-35 percent of the non-fossil organic carbon on the planet. Lignin hydrolyzing enzymes such as lignin peroxidase, laccase, manganese peroxidase, and others produce a variety of aromatic monomers, including ferulic and vanillic acids. However, very little research has been done on the role of microbes in lignin degradation. In the present work, we have isolated 25 ligninolytic bacteria and 25 ligninolytic fungi from organic soils of Koppal, Raichur districts of Karnataka. The bacterial isolates were identified as Pseudomonas putida, Bacillus subtilis, based on biochemical tests, and fungi were identified as Aspergillus niger, Trichoderma viridae, Phanerochaete chrysosporium and Pleurotus ostreatus based on morphological characters. The ligninolytic activity of bacterial isolates was high when compared to fungal isolates. All the isolates produced detectable amounts of lignin peroxidase, manganese peroxidase, and laccase under in vitro conditions. In dye decolorization test, fungal isolates KGST-1, KGST-2, and KKSP could decolorize Ramazol Brilliant Blue R and Congo red.