Biodelignification and humification of horticultural plant residues by fungi

The degradation of lignin in mixtures of horticultural plant residues with different C/N ratios by lignocellulolytic fungi was evaluated. Sterile sun-dried horticultural wastes were inoculated with Coriolus versicolor, Phanerochaete flavido-alba and Trichoderma koningii under controlled laboratory conditions and the fungal ligninolytic abilities compared and correlated with the humification process. The three fungi enhanced the formation of polymerized molecules, showing a trend similar to that commonly observed in soil humification processes. Lignin was degraded by all three, but to different degrees dependent on fungus and substrate composition. P. flavido-alba was the most active degrader, with a maximum lignin degradation rate of 46%. The efficiency of degradation was affected by the C/N ratio of the substrate, which was adjusted between 21 and 35 by addition of sawdust. Data showed that the tested fungi were effectively involved in humification and lignin degradation of horticultural wastes and might be used as inocula in a pre-treatment process before composting in order to reduce the resistance of the substrate to biodegradation.