Synthesis of galactooligosaccharides by Cryptococcus laurentii and Aspergillus oryzae using different kinds of acid whey

Abstract

Different kinds of acid whey, that is, casein whey, whey from traditional Greek yoghurt production, and concentrated acid whey permeate, were used to evaluate their potential for the synthesis of prebiotic galactooligosaccharides (GOS). Therefore, β-galactosidase from Cryptococcus laurentii was used in the form of a whole cell biocatalyst and characterised with regard to optimum temperature and pH, enzyme stability, substrate affinity, and the influence of various cations. The transgalactosylation activity was compared with that of a commercial preparation of Aspergillus oryzae β-galactosidase. With C. laurentii, high GOS yields of 34.6%–36.1% could be obtained in acid whey, while the yield with A. oryzae ranged from 8.8% to 19.6%. Using C. laurentii, the type of whey had an influence on GOS composition, because the enzyme is able to use galactose, which is present in Greek yoghurt whey, as an acceptor substrate.