Possibilities of application of six kinds of different expanded clay granules in biotechnology were evaluated. The granules were prepared and characterized in the Institute of Silicate Materials, Riga Technical University. The main raw material was clay obtained from three Latvian clay deposits. Adhesion of microorganisms onto expanded clay granules was studied. The Gram-negative saprophytic bacterium Pseudomonas putida MSCL 650 was chosen as a model because P. putida is widespread throughout the environment. The batch experiments were carried out in order to determine the number of viable number of bacteria (colony forming units – CFU) in the presence and absence of clay granules in the incubation liquid as well as in the suspension recovered from surface of granules after four hours long incubation at 30 C. The concentration of CFU was obtained using the serial dilution technique. Experimental data analysis showed that bacterial adhesion take place in all of the investigated expanded clay granules obtained from deposits of Liepa, Lode and Prometejs, and sintered at temperature of 1100-1200 C. However, only Lode granules were appropriate for the immobilization of live cells. It was ascertained that Prometejs granules possessed bactericidal action in the aquatic environment. Liepa granules showed comparatively small bactericidal action but Lode granules did not show any bactericidal activity. Electrical conductivity and pH of aquatic environment of granules was estimated and possible mechanisms of the established bactericidal activity were described. It was demonstrated that Prometejs granules increased the pH value of the liquid from 6.8 to 10.0 while Lode granules enhanced pH only by 0.2 units. Liquid medium of the Prometejs granules demonstrated also approximately six times greater electrical conductivity than medium of other granules. The results of the study suggest that Latvian clay and corresponding expanded clay materials are very different and therefore could be used in different fields of biotechnology.