Enzymatic synthesis of HMOs through transgalactosylation is an efficient way for production. Various donors, including p-nitrophenyl-β-galactopyranoside, uridine diphosphate galactose and lactose, can be used in transgalactosylation. In particular, lactose may act as either a donor or an acceptor in a variety of enzymatic reactions and is available in large quantities from the whey produced as a co-processing product from cheese production. There is a lack of published data, however, describing the large-scale production of such galacto-oligosaccharides.