Lignin in Paper Mill Sludge is degraded by White-Rot Fungi in Submerged Fermentation

Abstract

This study investigated biological treatment of paper mill sludge and lignin degradation by fungi. Four different Basidiomycetes white-rot fungi (WRF) were used: Coriolus versicolor, Tyromyces albidus, Trametes gallica and Pleurotus ostreatus. The fungi were cultured in submerged fermentation cultures with paper mill sludge. The pH values of the cultures and ligninolytic enzymes production profiles of the four fungi were monitored and reported here. The highest laccase activity of 202 U/L was obtained in T. albidus at day 25 while the maximum manganese-dependent peroxidase (MnP) activity of 50 U/L was obtained in C. versicolor from day 15 to 25. The P. ostreatus showed highest total cellulase activity with the peak of 0.26 μmol at day 15 while the other three WRF showed negligible total cellulase activity. The lignin contents were significantly decreased in the four WRF-treated sludge samples and were confirmed by acetyl bromide and FTIR analyses. The results suggested that lignin was preferentially used and significantly degraded or converted in all the four WRF-treated sludge samples.