A small-scale method for screening of lignin-degrading microorganisms

A new method to facilitate rapid screening of lignin-degrading microorganisms was developed. Fungal strains are cultivated in tissue culture plates containing C-ring-labeled dehydrogenation polymerizate (DHP) (synthetic lignin). Evolved CO(2) is trapped in barium-saturated filter paper and is detected by exposing the paper to X-ray film. Analysis of the autoradiograms, carried out by density measurement with an image analysis program, allows for a semiquantitative estimation of the amount of CO(2) evolved. The method is especially useful for screening for new, powerful lignin-degrading strains in both man-made and natural environments. It eliminates the need for special equipment for their cultivation and trapping of CO(2) as well as laborious sample analysis. The method has in this study been used to test three novel fungal isolates and a laccaseless mutant of the basidiomycete Pycnoporus cinnabarinus. Their ligninolytic capacities were compared with those of the potent lignin degrader Ceriporiopsis subvermispora.