Production of d-galactose using β-galactosidase and Saccharomyces cerevisiae entrapped in poly(vinylalcohol) hydrogel

d-Galactose was produced from lactose (200 g l−1) in the batch mode of a simultaneous saccharification and fermentation process (SSF). β-Galactosidases (from Kluyveromyces lactis and Aspergillus oryzae) and yeasts were immobilized in poly(vinylalcohol) hydrogel lens-shaped capsules – LentiKats®. After 20 repeated batch runs with entrapped K. lactis, β-galactosidase and free Saccharomyces cerevisiae (10% v/v inoculum), galactose productivity decreased to 50% and 1.4 kg of galactose were prepared. Compared to this, just 20% decrease of galactose productivity and a 0.9 kg production of galactose were observed for the SSF process with β-galactosidase from A. oryzae after 15 repeated batches under the same conditions. In the process of SSF with co-immobilized enzyme from K. lactis and S. cerevisiae, the galactose productivity increased from 3 g l−1 h−1 to 4.1 g l−1 h−1, which reduced the time of preparation of d-galactose.