The aim of this research was to analyze the antioxidant and prebiotic properties of lactobionic acid and to develop a method of producing it from whey using the bacterium Pseudomonas taetrolens. Prebiotic properties were tested with selected bacterial strains that exhibit probiotic properties, while the antioxidant efficacy was tested using cold-pressed rapeseed oil. A particularly evident prebiotic effect was observed with the bacterium Lactobacillus fermentum with a lactobionic acid concentration of 16 mg/cm(3). The growth curves of microorganisms in a substrate with various levels of lactobionic acid showed similarities between Lactococcus lactis, Lactobacillus acidophilus DSM 20242, Lactobacillus acidophilus L-AH1, Lactobacillus acidophilus NCDO, Lactobacillus delbrueckii A, Lactobacillus casei, Lactobacillus casei Shirota, Bifidobacterium bifidum DSM 20215, and Bifidobacterium bifidum DSM 20456, where a short logarithmic growth phase could be distinguished, in comparison to the growth of Lactobacillus fermentum and Lactobacillus acidophilus CH-5, where the logarithmic growth phase was extended. Bifidobacterium bifidum DSM 20082 and Bifidobacterium bifidum DSM 20239 form a separate group. The greater the amount of lactobionic acid added, the higher its activity. The greatest oxidation inhibition efficacy in rapeseed oil was recorded on day 10 of storage at 60 degrees C with an acid content of 10 mg/cm(3). Expressed as a percentage reduction of peroxide value, this effect was 19.6%. The best result for preparations of lactobionic acid were found at 1 cm(3) (22.03 mg/cm(3)), amounting to 7.3% on day 10 of the rapeseed oil thermostat test.