Abstract Unlike the P. shermanii and S. cerevisiae cultures, the study on the distribution of oxygen transfer in stirred bioreactor for P. chrysogenum free mycelia broths indicated that this process is controlled mainly by the high apparent viscosity of broths, and less by the presence of fungus biomass. For this reason, the influence of fungus accumulation on the reduction of kla is attenuated compared with that obtained for bacterial or yeasts broths. The lower influence of fungus biomass is also suggested by the higher value of the ratio (kla)C/(kla)0 for P. chrysogenum, which was for about 1.25 times greater than that for P. shermanii broths, respectively for about 1.15 greater compared with that for S. cerevisiae cultures, at 36 g/L d.w. and 450 W/m3. Similar to the previously studied systems, the analysis of kla distribution indicated its heterogeneity on the bioreactor height, the oxygen transfer rate increasing from position 1 to 4. Contrary to the bacterial and yeasts cultures, the intensification of aeration promoted the initial reduction of kla, which reached a maximum level, followed by its increase, due to the flooding phenomenon.