The sorption capacity of the cultures Trichosporon capitatum and Aspergillus niger towards zinc dissolved in the culture liquid was studied by radio active labelling. The curves of sorption kinetics and the so-called sorption quasi-isotherms showing the dependence of zinc sorption by the microbial biomass upon zinc concentration in the liquid medium were derived. For the Aspergillus niger culture at zinc concentrations of 0.5 to 52 mug/ml the sorption quasi-isotherm was linear. The zinc extraction by microorganisms was related not only to the physico-chemical sorption but also to the zinc accumulation in the cell biopolymers. The paper presents calculations of the microbiological purification of sewage waters from zinc by means of the Aspergillus niger culture.