Production of cellulases and xylanases by low-temperature basidiomycetes

Three of four isolates, representing phylogenetically distinct groupings of low-temperature basidiomycetes (LTB), were capable of utilizing wheat stra w, and to a lesser extent conifer wood at 15%C. A cottony snow mould LTB (L RS 013) and a fruit rot LTB (LRS 241) grown on straw significantly degraded filter paper, carboxymethylcellulose (CMC), p-nitrophenyl beta-glucopyrano side (i.e., beta-glucosidases), and xylan. Enzymes produced by Coprinus psy chromorbidus (LRS 067) were limited to xylanases from straw and wood and be ta-glucosidases from wood. A sclerotia-forming LTB (LRS 131) exhibited poor growth on both substrates, and did not produce detectable quantities of ex tracellular enzymes. None of the LTB isolates tested degraded avicel. The t emperature optima of CMCases and xylanases in the filtrates from the straw medium ranged from 25%C to 55%C, and with the exception of LRS 067, signifi cant activity was observed at 5%C. Two cellulases (25 and 31 kDa) and two x ylanases (24 and 34 kDa) were observed on zymograms for LRS 013 and 241. Re duction of enzymes with 2-mercaptoethanol adversely affected their activity on zymograms, and an additional cellulase band was observed for non-reduce d samples. This study indicates that LTB produce an array of cellulolytic a nd xylanolytic enzymes, and that some of these enzymes possess low-temperat ure optima which may facilitate degradation of plant fibre under low-temper ature conditions.