Isolation and screening of lignin-degrading microorganisms

Fifty lignocellulosic fungal strains were isolated from 100 different samples of decaying lignocellulosics collected from their natural habitats. As the bleaching of dye by fungi is an indication of their ligninolytic capability, an extensive screening programme was carried out to select the white-rot fungi having high ligninolytic capability using polymeric dye, Poly-R 478. Three fungal strains among the fifty isolates screened showed lignocellulosic activity. One of them, Fomes lignosus exhibited the highest ligninolytic activity on agar plates. They grew on agar plates with Poly-R and bleached the red colour of Poly-R to yellow, indicating that the isolated fungal strains have the capability of ligninolysis. A well known ligninolytic white-rot fungus Phanerochaete chrysosporium DSM 6909 was used as standard for comparison. It has been found that Fomes lignosus has the capability to bleach Poly-R dye significantly. In liquid culture with Poly-R, the bleaching capability of both strains was found to be pH dependent; maximum level of Poly-R bleaching occurred at pH 5.5 for P. chrysosporium and pH 4.5 for F. lignosus.