Effect of various carbohydrate substrates on the production of kefir grains for use as a novel baking starter

The propagation of kefir grains in a vigorously aerated, batch system, using various pure and mixed solutions of carbohydrates, was studied. From the experiments performed at 30 °C 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.