Degradation of natural lignins and lignocellulosic substrates by soil-inhabiting fungi imperfecti

The most powerful lignin-degraders among the 82 microbial strains isolated during a screening of ligninolytic microorganisms from forest soil were identified as Penicillium chrysogenum, Fusarium oxysporum and Fusarium solani. These fungi imperfecti mineralized 27.4%, 23.5% and 22.6% of C-14-labelled milled wood lignin (MWL) from wheat straw after 28 days of incubation in liquid media. Degradation of MWL from pine by P. chrysogenum was 8% and 19% when it was evaluated by spectrophotometry and Klason Lignin, respectively, but this substrate was hardly mineralized. All fungi were able to attack the hemicellulosic, cellulosic and also lignin fractions of wheat straw during solid-state fermentation, F. solani being capable of degrading about 25% of both carbohydrates and lignin. When the selected fungi were tested for dye decolourization, they all readily attacked the polymeric dye Remazol brilliant blue R (RBBR) and also poly R-478 to a minor extent.