Synthesis of galactosyl sucralose by β-galactosidase from Lactobacillus bulgaricus L3

The β-galactosidase gene was cloned from Lactobacillus bulgaricus L3 and expressed in Escherichia coli using the pET-21b vector. The recombinant enzyme was purified and applied to catalyze glycosyl transfer from lactose to sucralose, one of the most popular sweeteners. The influence of reaction parameters such as time and donor/acceptor molar ratios was investigated in detail. The dominant product reached a maximal yield of 41.0% at the lactose/sucralose ratio of 1.5:1 for 15 h. It was formed regioselectively and identified as β-galactosyl-(1 → 6)-sucralose by ESI-MS and NMR analysis. Also there were minor products formed (4.0%) based on further galactosylation of the major product. These novel produced chemicals were introduced with both sucralose residue and prebiotic β-(1 → 6) galactosyl linkage. They might combine functions of sweetener and prebiotics, and would act as novel functional food additives in the future.