Spray-drying has been investigated as a method for preparation of dry formulations of live bacteria with high viability and high cell density. The concept used in this study has been to disperse the bacteria in an aqueous polymer containing two-phase system (ATPS), compatible with the micro-organisms. The cells partition to one phase, which is separated from the other phase in a droplet dispersion or bi-continuous system. The exclusion of the dispersed phase and the bacteria from the particle surface is studied by ESCA (electron spectroscopy for chemical analysis), which gives an estimate of the molecular composition at the powders surface. A measure of the powder dissolution rate was obtained, this property was highly related to the molecular composition at the powder surface. The effect of additives was studied by adding disaccharides and proteins to the ATPS before drying. The probiotic bacteria Enterococcus faecium M74 and Lactobacillus plantarum have been used as model organisms for this study. The viability after drying and 5 weeks storage has been evaluated by plate counting and was found to be higher in the ATPS compared to when single phase polymer solutions were used as drying matrices. Comparisons were made with freeze-drying of the same systems and also the effect of cell status before the drying step has been evaluated.