The Cryptococcus albidus XLN-gene (encoding endo-1,4-beta-xylanase) was expressed in the yeast Pichia stipitis under the control of the PsADH2-promoter, which is activated under O-2 limitation. The resulting transformant produced endo-1,4-beta-xylanase after a shift to anoxic conditions. Endo-1,4-beta-xylanase production was enhanced by limited aeration after the shift. (C) 2000 Elsevier Science Inc. All rights reserved.