Co-immobilized carrier-free enzymes for lactose upgrading

The enzymatic production of lactofructose syrup from lactose coming from surplus whey represents a sound example of the circular economy. The production process requires the sequential action of two enzymes, namely β-galactosidase and glucose (xylose) isomerase, which can act independently in different reactors or a one-pot system. The latter is an interesting option, even more, if considering the co-immobilization of the enzymes involved in the biotransformation. This review analyzes the different options to carry out this process, with a focus on the key aspects of the co-immobilization of the enzymes in a carrier-free system and the operating conditions for such catalysts, which are key issues for developing a successful technology. The production of lactofructose syrup from lactose is an illustrative case study, but the analysis performed both on the preparation and use of the biocatalyst can be extrapolated to other co-immobilized multienzyme systems.