The propagation of kefir grains in a vigorously aerated, batch system, using variousipure and mixed solutions of carbohydrates, was studied. From the experiments performed at 30 degreesC with synthetic liquid media containing single sugars, the one containing fructose (pH 5.5 and 5 g/l initial kefir concentration), gave the largest biomass production (20.75 g) in a 24-h experiment. When mixtures of sugars where used, the one containing glucose and sucrose at a fixed-ratio of 1:3, was found to be the most effective, yielding 27.25 g of kefir biomass. Kinetics of sugar bioconversions were also studied. The obtained results are important for the prediction of effective, low-cost utilization of various food-grade wastes for the production of kefir biomass and its possible use as a novel baking starter. (C) 2004 Elsevier Ltd. All rights reserved.