INVESTIGATIONS ON PROTEINS EXCRETED BY THE YEAST HANSENULA-POLYMORPHA AND THEIR INFLUENCE ON BROTH FOAMINESS AND CELL RECOVERY BY FLOTATION

Hansenula polymorpha was cultivated in continuous culture in the absence of antifoam agents on synthetic medium under different cultivation conditions (29-degrees-C and 37-degrees-C, C-, N-, and P-limitation, C-limitation with and without amino acid supplement at different dilution rates). The cells were continuously recovered from the broth by foam flotation in a countercurrent bubble/foam column connected directly to the reactor. In order to investigate the influence of the proteins excreted by the cells on their flotation, the cells were removed from the broth, and the proteins were enriched and analyzed by SDS-PAAGE and native PAAGE. The foaminess of the protein fractions was determined as well. These investigations indicated that during cultivation various glycoproteins were excreted, which were distributed differently between the foam and the flotation residue liquids. A close relationship between the foaminess of the culture broth and the excreted proteins was observed. The possible collector effect of these proteins and the effect of excreted lipids are discussed as well.