MICROCHEMICAL STUDIES OF WOOD DEGRADATION BY BROWN-ROT AND WHITE-ROT FUNGI IN 2 TROPICAL TIMBERS

An observation that the growth of the brown rot fungus Gloeophyllum se piarium and another species of the same genus isolated from decaying t imbers-in-buildings, 'bleached' mahogany (Khaya ivorensis) timber, pro mpted a laboratory investigation of their pattern of wood degradation in obeche (Triplochiton scleroxylon) and mahogany. The white rot fungu s Pleurotus ostreatus was studied for comparison. Microchemical and qu antitative analyses indicated that the Gloeophyllum species degraded c ellulose, but not lignin. P. ostreatus attacked lignin after substanti ally degrading cellulose. Spot tests indicated laccase production by a ll three species studied. Lignin peroxidase was detected only with P. ostreatus. It is hypothesized that laccase may be partly associated wi th breakdown of the decay-retarding pigmented extractives of the timbe rs. 'Bleaching' may have been due to lightening of timber colour cause d by removal of these pigmented compounds. Copyright (C) 1996 Publishe d by Elsevier Science Limited.