WOOD DEGRADATION, AND CELLULASE AND LIGNINASE PRODUCTION, BY TRAMETESAND OTHER WOOD-INHABITING BASIDIOMYCETES FROM INDIGENOUS FORESTS OF ZIMBABWE

Nine species of Trametes and five other wood inhabiting basidiomycetes , were collected from the indigenous forests of Zimbabwe and analysed for cellulases, ligninases, extracellular phenolases and wood degradin g ability for the first time. Cellulase enzyme activities varied widel y among the species. After 15 d growth exo-glucanase activity had incr eased in the majority of species whilst Biter paper activity showed th e opposite trend, being greatly reduced in all species on day 15 compa red to day IO. Endo-glucanase activity was relatively uniform at both sampling times. The fungi were more active against water soluble cellu lose derivatives than filter paper cellulase. In all the fungi tested, cellulose activity on filter paper was significantly less than endo- and exo-glucanase activities. The highest cellulase activity was expre ssed by Cerrena meyenii (683 U mg(-1)) Phaeotrametes decipiens, Tramet es modesta, and T. pocas also expressed relatively high cellulase acti vity on all types of cellulose tested. All Trametes species tested pos itive for extracellular phenol oxidases whilst Fomotopsis spragueii an d Irpex stereoides tested negative. Ail but one of the Trametes specie s in the study were able to degrade two different lignin preparations in tests for lignin degradation. T. menziesii was unable to degrade bo th lignin preparations although it had tested positive for production of extracellular oxidase. The species in this study degraded hardwood to a greater extent than softwood. Eight of them caused more than 80% dry weight loss of wood blocks during 70 d incubation. Those fungi tha t expressed high cellulase activity also caused high weight loss on wo od.