A DNA fragment containing a transcription regulating region of the alcohol oxidase (AOX1) gene from the methylotrophic yeast Pichia pastoris was used in the construction of a vector for the expression of heterologous proteins in the methylotrophic yeast Hansenula polymorpha. We used this vector to clone the SUC2 gene from Saccharomyces cerevisiae into H. polymorpha yeast. The culture conditions for invertase production using a fed-batch culture were studied. More than 1.5 x 10(3) U/ml of biologically active invertase (1 g/l) were secreted to the cellular periplasmic space. The fermentative process was scaled up to 50 l. Invertase produced from H. polymorpha was glycosylated, but it contained significantly less carbohydrate than protein produced by S. cerevisiae. Using the Western-blot technique, it was observed that invertase secreted from H. polymorpha and invertase secreted from S. cerevisiae showed common antigenic determinants.