The nonionic surfactant Tween 80 (polyethylene oxide sorbitan mono-oleate) has been reported to increase enzyme production and/or secretion in bacteria and fungi. Such a procedure could greatly facilitate research into the physiology of wood-decay fungi since quantities of available enzyme are often limiting. The brown-rot fungus Postia placenta was grown in a synthetic medium supplemented with 0, 0.01, 0.05, 0.1, 0.2, and 0.4% Tween 80. The addition of even the lowest percentage of Tween significantly increased mycelial dry weight and prevented the formation of aerial hyphae. With the exceptions of ß-D-glucosidase and ß-D-galactosidase, extracellular carbohydrate-degrading enzyme production did not change. Levels of xylanase, carboxymethylcellulase, laminarinase, and ß-D-galactosidase remained unaffected by the presence of Tween. Some factor other than secretion mechanisms, such as microelement or nitrogen availability, is probably limiting production of these enzymes.

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