Monday, August 2, 2010
Pacific Concourse (Hyatt Regency San Francisco)
Resupinate white rot fungi (WRF) are abundant throughout tropical regions, but little is known about their potential as sources for novel lignolytic enzyme activity. In this study, tropical resupinate WRF were collected from dead-wood stumps in five different provinces of Thailand and screened for efficient lignin peroxidase (LiP) and lignocellulolytic enzyme production. Based on morphological characteristics, 25 of the resupinate WRF isolates were identified as members of the genera Bjerkandera, Ceriporia, Fomes, Hyphodontia, Junghuhnia, Macrohyporia, Oxyporous, Pachykytospora, Peniophora, Perenniporia, Phanaerochaete, and Schizopora. Among these isolates, lignin modifying enzymes (LMEs) were examined by direct visualization of specific color reactions using the compounds azure-B, phenol red or ABTS, which indicate production of lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase, respectively. Nineteen of the isolates screened tested positive for LMEs activity. Among these 19 isolates, nine were positive for LiP activity. Most of LiP-positive isolates were found to be able to produce cellulases and xylanase on plate assays using 1% CMC or 2% xylan as a substrate, respectively. For further characterization, selected WRF isolates were screened for LiP activity using an azure-B (0.01%) decolorization liquid assay. Four isolates, identified as strains of Peniophora sp., Phanerochaete sordida, Macrohyporia dictyopora and Schizopora apacheriensis, significantly decolorized azure-B up to 50% within 4 days. These results suggest that tropical resupinate WRF are a taxonomically diverse group and may represent a potential untapped source of novel lignocellulolytic enzyme producers.