Application relevant studies of fungal beta-galactosidases with potential application in the alleviation of lactose intolerance.

ABSTRACT

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 55 degrees C versus 65 degrees C were obtained. Unlike current commercialized supplemental lactases, both of the purified enzymes displayed significant stability when exposed to simulated gastric conditions, with beta-gal 1 in 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.