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Two isolates of wood-decay basidiomycetous fungi from the Sonoran Desert were selected from a preliminary screening of an extensive collection of wood-decay fungi. The isolates produced extracellular, alkaline-active carboxymethyl cellulase (CMCase) and filter paper cellulase activity, especially on solid substrates. Cultivation on wheat bran gave a higher cellulase yield than cultivation on corn steep liquor or paper pulp. The fungi produced alkaline-active cellulases when cultivated at pH 7.0 and 8.0, but not at pH 9.0 or above. Surfactants did not affect enzyme production level during cultivation on wheat bran. The fungi grew at 37 degrees C, but enzymes were produced at 27 degrees C. Isolate 2 produced more CMCase activity than did isolate 1 at both pH 7.0 and 8.5. In both isolates, enzyme activity was higher at pH 7.0 than at 8.5. Isolate 1 CMCase was stable at 50 degrees C and isolate 2 CMCase, at 60 degrees C. The crude alkaline enzymes could deink mixed office wastepaper that was 70% coated with toners. More ink was removed after addition of enzymes to paper pulp in the presence of surfactant.