The invention relates to a novel fructofuranosidase activity for obtaining the prebiotic oligosaccharide 6-kestose. One object of the invention is to characterize a novel transfructosylase activity which is associated with the extracellular invertase of Schwanniomyces occidentalis (specifically the strains selected from the group consisting of ATCC260077, ATCC7410 and ATCC20499) and which can be used to obtain prebiotic oligosaccharides, mainly 6-kestose, which are widely used in the food industry. Another object of the invention relates to the method for obtaining an enzymatic product as well as to the substantially pure enzyme with fructofuranosidase activity.