Functional screening studies revealed that Aspergillus carbonarius ATCC6276 produced extracellular beta-galactosidase activity potentially suited for use as a lactase digestive supplement in the treatment of lactose intolerance. The crude preparation contained two beta-galactosidase activities, beta-gal 1 and beta-gal 2, which were separated by ion-exchange chromatography. Both enzymes were purified to homogeneity by a combination of gel filtration, ion-exchange, chromatofocusing and hydrophobic interaction chromatographies. beta-gal 1 and beta-gal 2 displayed differences in molecular mass (110 kDa versus 120 kDa as judged by SDS PAGE) and in a range of additional physicochemical properties. Km values of 83 and 309 mM, respectively, were recorded using lactose as substrate while temperature optima of 55C versus 65C were obtained. Unlike current commercialized supplemental lactases, both of the purified enzymes displayed significant stability when exposed to simulated gastric conditions, with beta-gal 1in particular retaining 70% residual activity after exposure to pH 2.0 in the presence of pepsin for 2 h. Overall the results indicate that the beta-galactosidases of Aspergillus carbonarius ATCC6276, either individually or in combination, may be suitable for use as a digestive supplement for the alleviation of lactose intolerance.