Simultaneous hydrolysis of cheese whey and lactulose production catalyzed by β-galactosidase from Kluyveromyces lactis NRRL Y1564

摘要

beta-Galactosidase was produced by the yeast Kluyveromyces lactis NRRL Y1564 in cheese whey supplemented with yeast extract under the optimal temperature of 30 degrees C, delivering an enzymatic activity of 4418.37 U/g(cell) after 12 h of process. In order to develop more stable biocatalysts, the enzyme produced by fermentation was immobilized on 2.0% w/v chitosan activated with glutaraldehyde, epichlorohydrin or glycidol, producing a highly active and stable biocatalyst capable of hydrolyzing lactose and producing lactulose simultaneously. The biocatalyst obtained by immobilization in chitosan-glutaraldehyde showed high storage stabilities (100% of its activity when stored at 4 degrees C 105 days). Regarding the milk lactose hydrolysis by both the soluble and the immobilized enzyme, the conversions obtained were 38.0% and 42.8%, respectively. In this study, by using a biocatalyst deriving from enzyme immobilization to chitosan support, a lactulose production of 17.32 g/L was also possible.